Genetic variation developed in plant breeding programs is fundamental to creating new combinations that result in cultivars with enhanced characteristics. Over the years, tomato (Solanum lycopersicum) breeding program...Genetic variation developed in plant breeding programs is fundamental to creating new combinations that result in cultivars with enhanced characteristics. Over the years, tomato (Solanum lycopersicum) breeding programs associated with the Texas A&M University system have developed morphologically diverse lines of tomatoes selected for heat tolerance, fruit quality, and disease resistance to adapt them to Texas growing conditions. Here we explored the intraspecific genetic variations of 322 cultivated tomato genotypes, including 300 breeding lines developed by three Texas A&M breeding programs, as an initial step toward implementing molecular breeding approaches. Genotyping by sequencing using low coverage whole-genome sequencing (SkimGBS) identified 10,236 high-quality single-nucleotide polymorphisms (SNPs) that were used to assess genetic diversity, population structure, and phylogenetic relationship between genotypes and breeding programs. Model-based population structure analysis, phylogenetic tree construction, and principal component analysis indicated that the genotypes were grouped into two main clusters. Genetic distance analysis revealed greater genetic diversity? among the products of the three breeding programs. The germplasm developed at Texas A&M programs at Weslaco, College Station, and by Dr. Paul Leeper exhibited genetic diversity ranges of 0.175 - 0.434, 0.099 - 0.392, and 0.183 - 0.347, respectively, suggesting that there is enough variation within and between the lines from the three programs to perform selection for cultivar development. The SNPs identified here could be used to develop molecular tools for selecting various traits of interest and to select parents for future tomato breeding.展开更多
In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to ...In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.展开更多
This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed...This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.展开更多
This study aimed to investigate the differences in shoot and root traits, and water use and water use efficiency（WUE） in drought tolerant（DT） maize（Zea mays L.） hybrids under full and deficit irrigated condition...This study aimed to investigate the differences in shoot and root traits, and water use and water use efficiency（WUE） in drought tolerant（DT） maize（Zea mays L.） hybrids under full and deficit irrigated conditions. A two-year greenhouse study was conducted with four hybrids（one conventional hybrid, 33D53AM, two commercial DT hybrids, P1151 AM, N75H, and an experimental hybrid, Exp HB） grown under two water regimes（I（100） and I（50）, referring to 100 and 50% of evapotranspiration requirements）. Under water stress, the hybids P1151 AM, N75, and Exp HB showed more drought tolerance and had either greater shoot dry weight or less dry weight reduction than the conventional hybrid（33 D53 AM）. However, these three hybrids responded to water stress using different mechanisms. Compared with the conventional hybrid, the two commercial DT hybrids（P1151 AM and N75H） had a smaller leaf area, shoot dry weight, and root system per plant. As a result, these hybrids used less water but had a higher WUE compared with the conventional hybrid. In contrast, the experimental hybrid（ExpHB） produced more shoot biomass by silking stage at both irrigation levels than all other hybrids, but it had relatively lower WUE. The hybrids demonstrated different drought response mechanisms that may require different irrigation management strategies. More investigation and validation are needed under field conditions and in different soil types.展开更多
Streptococcus pneumoniae is a medically important pathogen capable of causing human infections of pneumonia, bacteremia, otitis media, and meningitis. Although there are vaccinations available, infections with S. pneu...Streptococcus pneumoniae is a medically important pathogen capable of causing human infections of pneumonia, bacteremia, otitis media, and meningitis. Although there are vaccinations available, infections with S. pneumoniae still remains a global problem. S. pneumoniae is a highly adaptable bacterial species with numerous serotypes based on capsular polysaccharides. The different serotypes vary in their ability to colonize and causing pathology. Here we compared the regulation of five different virulence factors from four common serotypes of S. pneumoniae that vary in their carriage, morbidity, and mortality rates in the human population using two different in vitro methods, broth and cell culture. We determine that there is variation of virulence factor gene regulation within a serotype using two different culture methods, and variation between the serotypes in the same culture condition. The regulation of genes appeared to have a correlation with the ability of the various serotypes to grow in broth culture, adhere to cultured lung cells, and invade the cultured lung cells, as serotypes that shared similar regulation of virulence factors tended to behave similarly in culture. Many studies with S. pneumoniae rely on the use of one selected serotype, but since there is a wide variation in the growth and regulatory mechanisms of these bacteria. As demonstrated here, future studies should utilize more strains in models before concluding mechanisms of pathobiology.展开更多
Recent technological advances in cotton(Gossypium hirsutum L.) phenotyping have offered tools to improve the efficiency of data collection and analysis.High-throughput phenotyping(HTP) is a non-destructive and rapid a...Recent technological advances in cotton(Gossypium hirsutum L.) phenotyping have offered tools to improve the efficiency of data collection and analysis.High-throughput phenotyping(HTP) is a non-destructive and rapid approach of monitoring and measuring multiple phenotypic traits related to the growth,yield,and adaptation to biotic or abiotic stress.Researchers have conducted extensive experiments on HTP and developed techniques including spectral,fluorescence,thermal,and three-dimensional imaging to measure the morphological,physiological,and pathological resistance traits of cotton.In addition,ground-based and aerial-based platforms were also developed to aid in the implementation of these HTP systems.This review paper highlights the techniques and recent developments for HTP in cotton,reviews the potential applications according to morphological and physiological traits of cotton,and compares the advantages and limitations of these HTP systems when used in cotton cropping systems.Overall,the use of HTP has generated many opportunities to accurately and efficiently measure and analyze diverse traits of cotton.However,because of its relative novelty,HTP has some limitations that constrains the ability to take full advantage of what it can offer.These challenges need to be addressed to increase the accuracy and utility of HTP,which can be done by integrating analytical techniques for big data and continuous advances in imaging.展开更多
The evaluation of rice （Oryza safiva L.） cultivars assists breeders in identifying useful trait relationships and in selecting parents as donors of specific traits. This study was conducted to compare long-grain ric...The evaluation of rice （Oryza safiva L.） cultivars assists breeders in identifying useful trait relationships and in selecting parents as donors of specific traits. This study was conducted to compare long-grain rice cultivars using genotype x trait （GT） biplot analysis and determine potential donors of traits related to grain yield and quality. Seventeen cultivars in the 2005 and 2006 Uniform Regional Rice Nursery in Beaumont, Texas, USA were analyzed for 20 traits using GT biplot analysis. The GT biplots showed the diversity among cultivars with regards to yield-related traits. Cultivars recommended as donor parents were： Trenasse, Spring, Presidio, and Cocodrie for high grain yield and head rice rate Trenasse and Presidio for semi-dwarfness; Banks for tall plant height; Wells for high flag leaf area, panicle weight, and number and mass of filled grains per panicle; Hidalgo for high tiller density; Francis for high number of spikelets per panicle; Spring and Trenasse for short flowering duration; Cheniere for more days to heading and maturity and Spring for less days; and Spring and Hidalgo for high grain weiqht. Breeders can use these cultivars with specific traits to increase qrain yield and quality.展开更多
Minor alleles(MA)have been associated with disease incidence in human studies,enabling the identification of diagnostic risk factors for various diseases.However,allelic mapping has rarely been performed in plant syst...Minor alleles(MA)have been associated with disease incidence in human studies,enabling the identification of diagnostic risk factors for various diseases.However,allelic mapping has rarely been performed in plant systems.The goal of this study was to determine whether a difference in MA prevalence is a strong enough risk factor to indicate a likely significant difference in disease resistance against white rust(WR;Albugo occidentalis)in spinach(Spinacia oleracea).We used WR disease severity ratings(WR-DSRs)in a diversity panel of 267 spinach accessions to define resistant-and susceptibility-associated groups within the distribution scores and then tested the single-nucleotide polymorphism(SNP)variants to interrogate the MA prevalence in the most susceptible(MS)vs.most resistant(MR)individuals using permutation-based allelic association tests.A total of 448 minor alleles associated with WR severity were identified in the comparison between the 25%MS and the 25%MR accessions,while the MA were generally similar between the two halves of the interquartile range.The minor alleles in the MS group were distributed across all six chromosomes and made up~71%of the markers that were also strongly associated with WR in parallel performed genome-wide association study.These results indicate that susceptibility may be highly determined by the disproportionate overrepresentation of minor alleles,which could be used to select for resistant plants.Furthermore,by focusing on the distribution tails,allelic mapping could be used to identify plant markers associated with quantitative traits on the most informative segments of the phenotypic distribution.展开更多
The soil extractant, H3A, has undergone several iterations to extract calcium (Ca), iron (Fe), aluminum (Al), potassium (K), phosphorus (P), ammonium (NH4-N) and nitrate (NO3-N) under ambient soil conditions. Few soil...The soil extractant, H3A, has undergone several iterations to extract calcium (Ca), iron (Fe), aluminum (Al), potassium (K), phosphorus (P), ammonium (NH4-N) and nitrate (NO3-N) under ambient soil conditions. Few soil extractants currently used by commercial and university soil testing laboratories can perform multi-nutrient extraction without over- or under-estimating at least one nutrient. Soil pH and plant root exudates have a strong influence on nutrient availability and H3A was developed to mimic soil conditions. Lithium citrate was previously used in the H3A formulation, but resulted in a cloudy supernatant in some samples, complicating laboratory analyses. In this study, we removed lithium citrate and compared the nutrients extracted from the modified (H3A-4) to the established (H3A-3) solutions. We found that the new extractant, H3A-4, produced a clear supernatant even in soils with low pH and high iron and aluminum concentrations. H3A-4 accurately predicts plant available nutrients and is a viable choice for commercial and laboratory settings due to its ease of use.展开更多
The Soil and Water Assessment Tool (SWAT) model has been successfully used to predict alterations in streamflow, evapotranspiration and soil water;however, it is not clear how effective or accurate SWAT is at predicti...The Soil and Water Assessment Tool (SWAT) model has been successfully used to predict alterations in streamflow, evapotranspiration and soil water;however, it is not clear how effective or accurate SWAT is at predicting crop growth. Previous research suggests that while the hydrologic balance in each watershed is accurately simulated with SWAT, the SWAT model over or under predicts crop yield relative to fertilizer inputs. The SWAT model now has three alternative N simulation options: 1) SWAT model with an added flush of N (SWAT-flush);2) N routines derived from the CENTURY model (SWAT-C);and 3) a one-pool C and N model (SWAT-One). The objective of this study was to evaluate the performance of SWAT-flush, SWAT-C, and SWAT-One as they affect wheat yield prediction. Simulated yields were compared to wheat yields in a 28-year fertilizer/wheat yield study in Lahoma, OK. Simulated yields were correlated with actual 28-year mean yield;however, none of the available N cycling models predicted yearly yields. SWAT-C simulated average yields were closer than other N sub-models to average actual yield. Annually there was a stronger correlation between SWAT-flush and actual yields than the other submodels. However, none of the N-cycling routines were able to accurately predict annual variability in yield at any fertilizer rate. We found that SWAT-C or SWAT-flush are the most viable choices for accurately simulating long-term average wheat yields although annual variations in yield prediction should be taken into consideration. Further research is needed to determine the effectiveness of SWAT-C and SWAT-flush in determining average and annual yield in various farming regions and with numerous agronomic crops.展开更多
A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was a...A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was aimed towards investigating the verde plant bug (<em>Creontiades signatus</em>) link between interior boll disease in Texas, USA. Using glasshouse grown bolls, bacteria recovered from locules with disease symptoms from field-grown cotton bolls caged with the piercing-sucking <em>C. signatus</em> were analyzed for the capacity to inflict the disease. For pathogenicity testing, spontaneously generated rifampicin resistant (Rifr) variants were utilized to track the antibiotic resistant bacterium and deter growth of endophytic and contaminating bacteria. To simulate <em>C. signatus</em> feeding, a needle (31 gauge) was employed to inoculate bolls at 13 - 15 days after flower bloom. Bacterial suspensions ranged from 10<sup>1</sup> - 10<sup>6</sup> colony forming units/ml. Field infection symptoms were duplicated after two weeks of bacterial exposure. Infectious strains were best categorized as <em>Serratia marcescens</em> based on traditional carbon utilization and enzyme production testing, and a 99% nucleotide sequence identity of 16S ribosomal DNA. Putative <em>S. marcescens</em> representatives isolated from rotted bolls exposed to<em> C. signatus</em> were shown to reproduce field infection symptoms upon inoculation into greenhouse grown fruit. <em>Serratia</em> spp. can inflict disease in alfalfa, cucurbits, and sunflower. The presented data are the first to definitively show that a <em>Serratia</em> sp. has the capacity to infect cotton.展开更多
The microbiome has a profound impact on host fitness. pH, oxygen, nutrients, or other factors such as food or pharmaceuticals, subject the microbiome to variations in the gastrointestinal tract. This variation is a ca...The microbiome has a profound impact on host fitness. pH, oxygen, nutrients, or other factors such as food or pharmaceuticals, subject the microbiome to variations in the gastrointestinal tract. This variation is a cause for concern given dysbiosis of the microbiome is correlated with various disease states. Currently, much research relies on model organisms to study microbial communities since intact microbiomes are challenging to utilize. The objective of this study is to culture an explanted colon microbiome of 4 Balb/c mice to develop an in vitro tool for future microbiome studies. We cultured homogenates of the distal colons of 4 mice in trans-well culture dishes. These dishes were incubated for 24 hours in two different oxygen concentration levels and the pH was compared before and after incubation of the cultures. To analyze the integrity of the microbiome, we utilized massively paralleled DNA sequencing with 16S metagenomics to characterize fecal and colon samples to speculate whether future studies may utilize feces in constructing an in vitro microbial community to spare animal lives. We found that pH and familial relationships had a profound impact on community structure while oxygen did not have a significant influence. The feces and the colon were similar in community profiles, which lends credence to utilizing feces in future studies. The gut microbiome is of great interest and great importance for studies in a variety of different diseases. Many laboratories do not have access to germ-free mice, which is one optimal way to study mammalian microbiomes, but this technique allowed for the in vitro culturing of a majority of the prokaryotes isolated from the colons of mice. This may allow an alternative to study the interactions of this very diverse population of microorganisms without the need for germ-free conditions.展开更多
Seven zoysiagrass genotypes were evaluated for salt tolerance in a greenhouse study.The plant materials included Zoysia matrella'Diamond',Z.japonica'Palisades',three Z.matrella×Z.japonica hybrids ...Seven zoysiagrass genotypes were evaluated for salt tolerance in a greenhouse study.The plant materials included Zoysia matrella'Diamond',Z.japonica'Palisades',three Z.matrella×Z.japonica hybrids DALZ 1701,DALZ 1713,and'Innovation',and two Z.minima×Z.matrella hybrids(DALZ 1309 and'Lazer').Treatments included a control(nutrient solution)and two saline treatments representing moderate and high salt levels.The electrical conductivity(EC)was 1.3 dS m−1 for control and moderate(EC5)and high salinity(EC10)were 5.0 and 10.0 dS m−1,respectively.At the end of eight-weeks of treatment,the relative(percent control)shoot dry weight(DW)was greatest in'Diamond'in EC10,and the relative root DW was greatest in DALZ 1309 in EC5.A cluster analysis based on the relative tissue dry weight identified'Diamond',DALZ 1309,and DALZ 1713 as the most salt tolerant genotypes.Additionally,the green leaf area(GLA)index of'Diamond'and DALZ 1713 were 98.8%and 100%,respectively,indicating excellent visual appearance under high salt levels.Bi-weekly clipping DW showed that'Diamond'continued to produce biomass throughout the duration of the study under the EC10 treatment.Sodium(Na^(+))and chloride(Cl−)content in the shoot tissue of the seven turfgrass genotypes indicated that lower concentrations corresponded to greater salt tolerance indicating exclusion of Na+and Cl−from the shoot tissue.Taken together,the genotypes'Diamond'and DALZ 1713 were determined to be the most salt tolerant and recommended for use in areas with high soil or water salinity.展开更多
Modern technologies and information tools can be used to maximize agricultural aviation productivity allowing for precision application of agrochemical products.This paper reviews and summarizes the state-of-the-art i...Modern technologies and information tools can be used to maximize agricultural aviation productivity allowing for precision application of agrochemical products.This paper reviews and summarizes the state-of-the-art in precision agricultural aviation technology highlighting remote sensing,aerial spraying and ground verification technologies.Further,the authors forecast the future of precision agricultural aviation technology with key development directions in precision agricultural aviation technologies,such as real-time image processing,variable-rate spraying,multi-sensor data fusion and RTK differential positioning,and other supporting technologies for UAV-based aerial spraying.This review is expected to provide references for peers by summarizing the history and achievements,and encourage further development of precision agricultural aviation technologies.展开更多
Dendrobium officinale has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway.In this study,D.officinale were grown aeroponically with light/dark cycles of 12 h/1...Dendrobium officinale has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway.In this study,D.officinale were grown aeroponically with light/dark cycles of 12 h/12 h,4 h/4 h,and 2 h/2 h for 150 d.The photosynthetic electron transfer characteristics,photosynthetic CO_(2) fixation pathways,and accumulations of biomass and soluble polysaccharides in D.officinale leaves were studied.The results showed that the photosynthetic apparatus states of D.officinale in aeroponic cultivation under short light/dark cycles of 4 h/4 h and 2 h/2 h were better than that under 12 h/12 h.The dark net CO_(2) exchange percentages of D.officinale were negative in short light/dark cycles of 4 h/4 h and 2 h/2 h,and the daily net CO_(2) exchange amount and dry/fresh weight increases were doubled compared with those in 12 h/12 h light/dark cycle.High soluble polysaccharides content and the soluble polysaccharides yield of D.officinale were obtained in the shorter light/dark cycle of 2 h/2 h.Therefore,the photosynthetic pathway of D.officinale could be switched from CAM to C3 by short light/dark cycles of 4 h/4 h and 2 h/2 h,and its higher biomass accumulation and soluble polysaccharides yield could be obtained by the shorter light/dark cycle of 2 h/2 h in aeroponic cultivation.展开更多
Virus-induced gene silencing （VIGS） offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resista...Virus-induced gene silencing （VIGS） offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticfllium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line （CA4002） with partial resistance to Verticillium wilt, and GhMKK2 and Gh Ve I are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases （SERKs） with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.展开更多
Cotton defoliation and post-harvest destruction are important cultural practices for cotton production.Cotton root rot is a serious and destructive disease that affects cotton yield and lint quality.This paper present...Cotton defoliation and post-harvest destruction are important cultural practices for cotton production.Cotton root rot is a serious and destructive disease that affects cotton yield and lint quality.This paper presents an overview and summary of the methodologies and results on the use of remote sensing technology for evaluating cotton defoliation and regrowth control methods and for assessing cotton root rot infection based on published studies.Ground reflectance spectra and airborne multispectral and hyperspectral imagery were used in these studies.Ground reflectance spectra effectively separated different levels of defoliation and airborne multispectral imagery permitted both visual and quantitative differentiations among defoliation treatments.Both ground reflectance and airborne imagery were able to differentiate cotton regrowth among different herbicide treatments for cotton stalk destruction.Airborne multispectral and hyperspectral imagery accurately identified root rot-infected areas within cotton fields.Results from these studies indicate that remote sensing can be a useful tool for evaluating the effectiveness of cotton defoliation and regrowth control strategies and for detecting and mapping root rot damage in cotton fields.Compared with traditional visual observations and ground measurements,remote sensing techniques have the potential for effective and accurate assessments of various cotton production operations and pest conditions.展开更多
Switchgrass （Panicum virgaturn L.） has been proposed as a sustainable bioenergy crop because of its high yield potential, adap- tation to marginal sites, and tolerance to water and nutrient limitations. A better und...Switchgrass （Panicum virgaturn L.） has been proposed as a sustainable bioenergy crop because of its high yield potential, adap- tation to marginal sites, and tolerance to water and nutrient limitations. A better understanding of the potential effects of biomass energy crop production practices on soil biological properties and organic matter dynamics is critical to its production. Our objective was to evaluate changes in C pools under a warm-season perennial switchgrass in different soils compared to typically-grown crops col- lected at College Station, Dallas, and Stephenville, TX in February 2001. Sampling depths were 0-5, 5-15, and 15-30 cm. Switchgrass increased soil organic C （SOC）, soil microbial biomass C （SMBC）, mineralizable C, and particulate organic matter C （POM-C） com- pared to conventional cropping systems. Soil C concentrations were in the order： long-term coastal bermudagrass [Cynodon dactylon （L.） Pers.] 〉 switchgrass or kleingrass （Panicum coloratura L.） planted in 1992 〉 switchgrass 1997 〉 conventional cropping systems. Soil C concentrations tended to increase with increasing clay content. Greater microbial biomass C followed the order of Dallas 〉 College Station 〉 Stephenville, and ranged from approximately 180 mg C kg-1 soil at Stephenville to 1 900 mg C kg-1 soil at Dallas. Particulate organic C was more sensitive than other fractions to management, increasing as much as 6-fold under long-term coastal bermudagrass compared to conventional cropping systems. Our study indicated that conversion of conventional cropping systems into switchgrass production can sequestrate more SOC and improve soil biological properties in the southern USA.展开更多
文摘Genetic variation developed in plant breeding programs is fundamental to creating new combinations that result in cultivars with enhanced characteristics. Over the years, tomato (Solanum lycopersicum) breeding programs associated with the Texas A&M University system have developed morphologically diverse lines of tomatoes selected for heat tolerance, fruit quality, and disease resistance to adapt them to Texas growing conditions. Here we explored the intraspecific genetic variations of 322 cultivated tomato genotypes, including 300 breeding lines developed by three Texas A&M breeding programs, as an initial step toward implementing molecular breeding approaches. Genotyping by sequencing using low coverage whole-genome sequencing (SkimGBS) identified 10,236 high-quality single-nucleotide polymorphisms (SNPs) that were used to assess genetic diversity, population structure, and phylogenetic relationship between genotypes and breeding programs. Model-based population structure analysis, phylogenetic tree construction, and principal component analysis indicated that the genotypes were grouped into two main clusters. Genetic distance analysis revealed greater genetic diversity? among the products of the three breeding programs. The germplasm developed at Texas A&M programs at Weslaco, College Station, and by Dr. Paul Leeper exhibited genetic diversity ranges of 0.175 - 0.434, 0.099 - 0.392, and 0.183 - 0.347, respectively, suggesting that there is enough variation within and between the lines from the three programs to perform selection for cultivar development. The SNPs identified here could be used to develop molecular tools for selecting various traits of interest and to select parents for future tomato breeding.
基金funded by the National Scientific and Technological Supporting Scheme,China (2013BAD05B02 )the Demonstration Plan of Modern Agriculture of Chinese Academy of Sciences (CXJQ120108-2)the support by the Sino-German Center for Research Promotion,Germany (GZ 1149)
文摘In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.
基金supported by the National Natural Science Foundation of China(Grant No.51069017)the International Collaborative Research Program of Xinjiang Science and Technology Commission(Grant No.20126013)
文摘This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.
基金supported in part by the UDSA-Ogallala Aquifer ProgramTexas A&M Agri Life Research Cropping System Program, USAthe USDA National Institute of Food and Agriculture Hatch Project, USA (TEX09438)
文摘This study aimed to investigate the differences in shoot and root traits, and water use and water use efficiency（WUE） in drought tolerant（DT） maize（Zea mays L.） hybrids under full and deficit irrigated conditions. A two-year greenhouse study was conducted with four hybrids（one conventional hybrid, 33D53AM, two commercial DT hybrids, P1151 AM, N75H, and an experimental hybrid, Exp HB） grown under two water regimes（I（100） and I（50）, referring to 100 and 50% of evapotranspiration requirements）. Under water stress, the hybids P1151 AM, N75, and Exp HB showed more drought tolerance and had either greater shoot dry weight or less dry weight reduction than the conventional hybrid（33 D53 AM）. However, these three hybrids responded to water stress using different mechanisms. Compared with the conventional hybrid, the two commercial DT hybrids（P1151 AM and N75H） had a smaller leaf area, shoot dry weight, and root system per plant. As a result, these hybrids used less water but had a higher WUE compared with the conventional hybrid. In contrast, the experimental hybrid（ExpHB） produced more shoot biomass by silking stage at both irrigation levels than all other hybrids, but it had relatively lower WUE. The hybrids demonstrated different drought response mechanisms that may require different irrigation management strategies. More investigation and validation are needed under field conditions and in different soil types.
文摘Streptococcus pneumoniae is a medically important pathogen capable of causing human infections of pneumonia, bacteremia, otitis media, and meningitis. Although there are vaccinations available, infections with S. pneumoniae still remains a global problem. S. pneumoniae is a highly adaptable bacterial species with numerous serotypes based on capsular polysaccharides. The different serotypes vary in their ability to colonize and causing pathology. Here we compared the regulation of five different virulence factors from four common serotypes of S. pneumoniae that vary in their carriage, morbidity, and mortality rates in the human population using two different in vitro methods, broth and cell culture. We determine that there is variation of virulence factor gene regulation within a serotype using two different culture methods, and variation between the serotypes in the same culture condition. The regulation of genes appeared to have a correlation with the ability of the various serotypes to grow in broth culture, adhere to cultured lung cells, and invade the cultured lung cells, as serotypes that shared similar regulation of virulence factors tended to behave similarly in culture. Many studies with S. pneumoniae rely on the use of one selected serotype, but since there is a wide variation in the growth and regulatory mechanisms of these bacteria. As demonstrated here, future studies should utilize more strains in models before concluding mechanisms of pathobiology.
基金National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2014BAD06B01-17)National Natural Science Foundation of China(41301471)International Postdoctoral Exchange Fellowship Program(20130043)
文摘Recent technological advances in cotton(Gossypium hirsutum L.) phenotyping have offered tools to improve the efficiency of data collection and analysis.High-throughput phenotyping(HTP) is a non-destructive and rapid approach of monitoring and measuring multiple phenotypic traits related to the growth,yield,and adaptation to biotic or abiotic stress.Researchers have conducted extensive experiments on HTP and developed techniques including spectral,fluorescence,thermal,and three-dimensional imaging to measure the morphological,physiological,and pathological resistance traits of cotton.In addition,ground-based and aerial-based platforms were also developed to aid in the implementation of these HTP systems.This review paper highlights the techniques and recent developments for HTP in cotton,reviews the potential applications according to morphological and physiological traits of cotton,and compares the advantages and limitations of these HTP systems when used in cotton cropping systems.Overall,the use of HTP has generated many opportunities to accurately and efficiently measure and analyze diverse traits of cotton.However,because of its relative novelty,HTP has some limitations that constrains the ability to take full advantage of what it can offer.These challenges need to be addressed to increase the accuracy and utility of HTP,which can be done by integrating analytical techniques for big data and continuous advances in imaging.
基金funded by the Texas Rice Research Foundation and by Lloyd T. WILSON through the Jack B. WENDT Endowed Chair
文摘The evaluation of rice （Oryza safiva L.） cultivars assists breeders in identifying useful trait relationships and in selecting parents as donors of specific traits. This study was conducted to compare long-grain rice cultivars using genotype x trait （GT） biplot analysis and determine potential donors of traits related to grain yield and quality. Seventeen cultivars in the 2005 and 2006 Uniform Regional Rice Nursery in Beaumont, Texas, USA were analyzed for 20 traits using GT biplot analysis. The GT biplots showed the diversity among cultivars with regards to yield-related traits. Cultivars recommended as donor parents were： Trenasse, Spring, Presidio, and Cocodrie for high grain yield and head rice rate Trenasse and Presidio for semi-dwarfness; Banks for tall plant height; Wells for high flag leaf area, panicle weight, and number and mass of filled grains per panicle; Hidalgo for high tiller density; Francis for high number of spikelets per panicle; Spring and Trenasse for short flowering duration; Cheniere for more days to heading and maturity and Spring for less days; and Spring and Hidalgo for high grain weiqht. Breeders can use these cultivars with specific traits to increase qrain yield and quality.
基金supported in part by funds from USDA-NIFA SCRI 2017-51181-26830 and a Texas A&M AgriLife Research Vegetable Seed Grant 124353-96181 to C.A.A.,as well as a Texas A&M AgriLife Research Insect-vectored Disease Seed Grants(114,190-96,210)to K.K.M.
文摘Minor alleles(MA)have been associated with disease incidence in human studies,enabling the identification of diagnostic risk factors for various diseases.However,allelic mapping has rarely been performed in plant systems.The goal of this study was to determine whether a difference in MA prevalence is a strong enough risk factor to indicate a likely significant difference in disease resistance against white rust(WR;Albugo occidentalis)in spinach(Spinacia oleracea).We used WR disease severity ratings(WR-DSRs)in a diversity panel of 267 spinach accessions to define resistant-and susceptibility-associated groups within the distribution scores and then tested the single-nucleotide polymorphism(SNP)variants to interrogate the MA prevalence in the most susceptible(MS)vs.most resistant(MR)individuals using permutation-based allelic association tests.A total of 448 minor alleles associated with WR severity were identified in the comparison between the 25%MS and the 25%MR accessions,while the MA were generally similar between the two halves of the interquartile range.The minor alleles in the MS group were distributed across all six chromosomes and made up~71%of the markers that were also strongly associated with WR in parallel performed genome-wide association study.These results indicate that susceptibility may be highly determined by the disproportionate overrepresentation of minor alleles,which could be used to select for resistant plants.Furthermore,by focusing on the distribution tails,allelic mapping could be used to identify plant markers associated with quantitative traits on the most informative segments of the phenotypic distribution.
文摘The soil extractant, H3A, has undergone several iterations to extract calcium (Ca), iron (Fe), aluminum (Al), potassium (K), phosphorus (P), ammonium (NH4-N) and nitrate (NO3-N) under ambient soil conditions. Few soil extractants currently used by commercial and university soil testing laboratories can perform multi-nutrient extraction without over- or under-estimating at least one nutrient. Soil pH and plant root exudates have a strong influence on nutrient availability and H3A was developed to mimic soil conditions. Lithium citrate was previously used in the H3A formulation, but resulted in a cloudy supernatant in some samples, complicating laboratory analyses. In this study, we removed lithium citrate and compared the nutrients extracted from the modified (H3A-4) to the established (H3A-3) solutions. We found that the new extractant, H3A-4, produced a clear supernatant even in soils with low pH and high iron and aluminum concentrations. H3A-4 accurately predicts plant available nutrients and is a viable choice for commercial and laboratory settings due to its ease of use.
文摘The Soil and Water Assessment Tool (SWAT) model has been successfully used to predict alterations in streamflow, evapotranspiration and soil water;however, it is not clear how effective or accurate SWAT is at predicting crop growth. Previous research suggests that while the hydrologic balance in each watershed is accurately simulated with SWAT, the SWAT model over or under predicts crop yield relative to fertilizer inputs. The SWAT model now has three alternative N simulation options: 1) SWAT model with an added flush of N (SWAT-flush);2) N routines derived from the CENTURY model (SWAT-C);and 3) a one-pool C and N model (SWAT-One). The objective of this study was to evaluate the performance of SWAT-flush, SWAT-C, and SWAT-One as they affect wheat yield prediction. Simulated yields were compared to wheat yields in a 28-year fertilizer/wheat yield study in Lahoma, OK. Simulated yields were correlated with actual 28-year mean yield;however, none of the available N cycling models predicted yearly yields. SWAT-C simulated average yields were closer than other N sub-models to average actual yield. Annually there was a stronger correlation between SWAT-flush and actual yields than the other submodels. However, none of the N-cycling routines were able to accurately predict annual variability in yield at any fertilizer rate. We found that SWAT-C or SWAT-flush are the most viable choices for accurately simulating long-term average wheat yields although annual variations in yield prediction should be taken into consideration. Further research is needed to determine the effectiveness of SWAT-C and SWAT-flush in determining average and annual yield in various farming regions and with numerous agronomic crops.
文摘A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was aimed towards investigating the verde plant bug (<em>Creontiades signatus</em>) link between interior boll disease in Texas, USA. Using glasshouse grown bolls, bacteria recovered from locules with disease symptoms from field-grown cotton bolls caged with the piercing-sucking <em>C. signatus</em> were analyzed for the capacity to inflict the disease. For pathogenicity testing, spontaneously generated rifampicin resistant (Rifr) variants were utilized to track the antibiotic resistant bacterium and deter growth of endophytic and contaminating bacteria. To simulate <em>C. signatus</em> feeding, a needle (31 gauge) was employed to inoculate bolls at 13 - 15 days after flower bloom. Bacterial suspensions ranged from 10<sup>1</sup> - 10<sup>6</sup> colony forming units/ml. Field infection symptoms were duplicated after two weeks of bacterial exposure. Infectious strains were best categorized as <em>Serratia marcescens</em> based on traditional carbon utilization and enzyme production testing, and a 99% nucleotide sequence identity of 16S ribosomal DNA. Putative <em>S. marcescens</em> representatives isolated from rotted bolls exposed to<em> C. signatus</em> were shown to reproduce field infection symptoms upon inoculation into greenhouse grown fruit. <em>Serratia</em> spp. can inflict disease in alfalfa, cucurbits, and sunflower. The presented data are the first to definitively show that a <em>Serratia</em> sp. has the capacity to infect cotton.
文摘The microbiome has a profound impact on host fitness. pH, oxygen, nutrients, or other factors such as food or pharmaceuticals, subject the microbiome to variations in the gastrointestinal tract. This variation is a cause for concern given dysbiosis of the microbiome is correlated with various disease states. Currently, much research relies on model organisms to study microbial communities since intact microbiomes are challenging to utilize. The objective of this study is to culture an explanted colon microbiome of 4 Balb/c mice to develop an in vitro tool for future microbiome studies. We cultured homogenates of the distal colons of 4 mice in trans-well culture dishes. These dishes were incubated for 24 hours in two different oxygen concentration levels and the pH was compared before and after incubation of the cultures. To analyze the integrity of the microbiome, we utilized massively paralleled DNA sequencing with 16S metagenomics to characterize fecal and colon samples to speculate whether future studies may utilize feces in constructing an in vitro microbial community to spare animal lives. We found that pH and familial relationships had a profound impact on community structure while oxygen did not have a significant influence. The feces and the colon were similar in community profiles, which lends credence to utilizing feces in future studies. The gut microbiome is of great interest and great importance for studies in a variety of different diseases. Many laboratories do not have access to germ-free mice, which is one optimal way to study mammalian microbiomes, but this technique allowed for the in vitro culturing of a majority of the prokaryotes isolated from the colons of mice. This may allow an alternative to study the interactions of this very diverse population of microorganisms without the need for germ-free conditions.
基金Funding for this project is provided by USDA NIFA to Project No.2017-68007-26318through the Agriculture and Food Research Initiative,Water for Agricultural Challenge Area,and hatch project TEX07726.
文摘Seven zoysiagrass genotypes were evaluated for salt tolerance in a greenhouse study.The plant materials included Zoysia matrella'Diamond',Z.japonica'Palisades',three Z.matrella×Z.japonica hybrids DALZ 1701,DALZ 1713,and'Innovation',and two Z.minima×Z.matrella hybrids(DALZ 1309 and'Lazer').Treatments included a control(nutrient solution)and two saline treatments representing moderate and high salt levels.The electrical conductivity(EC)was 1.3 dS m−1 for control and moderate(EC5)and high salinity(EC10)were 5.0 and 10.0 dS m−1,respectively.At the end of eight-weeks of treatment,the relative(percent control)shoot dry weight(DW)was greatest in'Diamond'in EC10,and the relative root DW was greatest in DALZ 1309 in EC5.A cluster analysis based on the relative tissue dry weight identified'Diamond',DALZ 1309,and DALZ 1713 as the most salt tolerant genotypes.Additionally,the green leaf area(GLA)index of'Diamond'and DALZ 1713 were 98.8%and 100%,respectively,indicating excellent visual appearance under high salt levels.Bi-weekly clipping DW showed that'Diamond'continued to produce biomass throughout the duration of the study under the EC10 treatment.Sodium(Na^(+))and chloride(Cl−)content in the shoot tissue of the seven turfgrass genotypes indicated that lower concentrations corresponded to greater salt tolerance indicating exclusion of Na+and Cl−from the shoot tissue.Taken together,the genotypes'Diamond'and DALZ 1713 were determined to be the most salt tolerant and recommended for use in areas with high soil or water salinity.
文摘Modern technologies and information tools can be used to maximize agricultural aviation productivity allowing for precision application of agrochemical products.This paper reviews and summarizes the state-of-the-art in precision agricultural aviation technology highlighting remote sensing,aerial spraying and ground verification technologies.Further,the authors forecast the future of precision agricultural aviation technology with key development directions in precision agricultural aviation technologies,such as real-time image processing,variable-rate spraying,multi-sensor data fusion and RTK differential positioning,and other supporting technologies for UAV-based aerial spraying.This review is expected to provide references for peers by summarizing the history and achievements,and encourage further development of precision agricultural aviation technologies.
基金supported by China Agriculture Research System(Grant No.CARS-21)National Natural Science Foundation of China(Grant No.31372089)。
文摘Dendrobium officinale has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway.In this study,D.officinale were grown aeroponically with light/dark cycles of 12 h/12 h,4 h/4 h,and 2 h/2 h for 150 d.The photosynthetic electron transfer characteristics,photosynthetic CO_(2) fixation pathways,and accumulations of biomass and soluble polysaccharides in D.officinale leaves were studied.The results showed that the photosynthetic apparatus states of D.officinale in aeroponic cultivation under short light/dark cycles of 4 h/4 h and 2 h/2 h were better than that under 12 h/12 h.The dark net CO_(2) exchange percentages of D.officinale were negative in short light/dark cycles of 4 h/4 h and 2 h/2 h,and the daily net CO_(2) exchange amount and dry/fresh weight increases were doubled compared with those in 12 h/12 h light/dark cycle.High soluble polysaccharides content and the soluble polysaccharides yield of D.officinale were obtained in the shorter light/dark cycle of 2 h/2 h.Therefore,the photosynthetic pathway of D.officinale could be switched from CAM to C3 by short light/dark cycles of 4 h/4 h and 2 h/2 h,and its higher biomass accumulation and soluble polysaccharides yield could be obtained by the shorter light/dark cycle of 2 h/2 h in aeroponic cultivation.
基金supported by funds from the Texas AgriLife Research Cotton Improvement Program to J.D.,T.W.,P.H., and L.S.the USDA National Institute of Food and Agriculture(Agriculture and Food Research Initiative Competitive Grants Program grant no.2012-67013-19433) to P.H.+1 种基金L.S.A.K.was supported by the NSF REU programF.L.was supported by the China Scholarship Council
文摘Virus-induced gene silencing （VIGS） offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticfllium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line （CA4002） with partial resistance to Verticillium wilt, and GhMKK2 and Gh Ve I are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases （SERKs） with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.
文摘Cotton defoliation and post-harvest destruction are important cultural practices for cotton production.Cotton root rot is a serious and destructive disease that affects cotton yield and lint quality.This paper presents an overview and summary of the methodologies and results on the use of remote sensing technology for evaluating cotton defoliation and regrowth control methods and for assessing cotton root rot infection based on published studies.Ground reflectance spectra and airborne multispectral and hyperspectral imagery were used in these studies.Ground reflectance spectra effectively separated different levels of defoliation and airborne multispectral imagery permitted both visual and quantitative differentiations among defoliation treatments.Both ground reflectance and airborne imagery were able to differentiate cotton regrowth among different herbicide treatments for cotton stalk destruction.Airborne multispectral and hyperspectral imagery accurately identified root rot-infected areas within cotton fields.Results from these studies indicate that remote sensing can be a useful tool for evaluating the effectiveness of cotton defoliation and regrowth control strategies and for detecting and mapping root rot damage in cotton fields.Compared with traditional visual observations and ground measurements,remote sensing techniques have the potential for effective and accurate assessments of various cotton production operations and pest conditions.
基金Supported by the Department of Energy Bioenergy Feedstock Development Program at Oak Ridge National Laboratory, USA(No. 19XSY091C)the Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS), USA
文摘Switchgrass （Panicum virgaturn L.） has been proposed as a sustainable bioenergy crop because of its high yield potential, adap- tation to marginal sites, and tolerance to water and nutrient limitations. A better understanding of the potential effects of biomass energy crop production practices on soil biological properties and organic matter dynamics is critical to its production. Our objective was to evaluate changes in C pools under a warm-season perennial switchgrass in different soils compared to typically-grown crops col- lected at College Station, Dallas, and Stephenville, TX in February 2001. Sampling depths were 0-5, 5-15, and 15-30 cm. Switchgrass increased soil organic C （SOC）, soil microbial biomass C （SMBC）, mineralizable C, and particulate organic matter C （POM-C） com- pared to conventional cropping systems. Soil C concentrations were in the order： long-term coastal bermudagrass [Cynodon dactylon （L.） Pers.] 〉 switchgrass or kleingrass （Panicum coloratura L.） planted in 1992 〉 switchgrass 1997 〉 conventional cropping systems. Soil C concentrations tended to increase with increasing clay content. Greater microbial biomass C followed the order of Dallas 〉 College Station 〉 Stephenville, and ranged from approximately 180 mg C kg-1 soil at Stephenville to 1 900 mg C kg-1 soil at Dallas. Particulate organic C was more sensitive than other fractions to management, increasing as much as 6-fold under long-term coastal bermudagrass compared to conventional cropping systems. Our study indicated that conversion of conventional cropping systems into switchgrass production can sequestrate more SOC and improve soil biological properties in the southern USA.
