Search

Aflatoxin production by isolates of Aspergillus flavus varies, ranging from highly toxigenic to completely atoxigenic. Several mechanisms have been identified which regulate aflatoxin production including medium carbon source and oxidative stress. In recent studies, aflatoxin production has been implicated in partially ameliorating oxidative stress in A. flavus. To better understand the role of aflatoxin production in oxidative stress responses, a selection of toxigenic and atoxigenic isolates of A. flavus with moderate to high oxidative stress tolerance were exposed to increasing concentrations of H2O2 in both aflatoxin-conducive and non-conducive media. Mycelial mats were collected for global transcriptome sequencing followed by differential expression, functional prediction, and weighted co-expression analyses. Oxidative stress and medium carbon source had a significant effect on the expression of several secondary metabolite gene clusters including those for aflatoxin, aflatrem, aflavarin, cyclopiazonic acid, and kojic acid. Atoxigenic biological control isolates showed less differential expression under stress than other atoxigenic isolates suggesting expression profiles may be useful in screening. Increasing stress also resulted in regulation of SakA/Hog1 and MpkA MAP kinase signalling pathways pointing to their potential roles in regulating oxidative stress responses. Their expression was also influenced by medium carbon source. These results suggest that aflatoxin production along with that of other mycotoxins may occur as part of a concerted coping mechanism for oxidative stress and its effects in the environment. This mechanism is also regulated by availability of simple sugars and glycolytic compounds for their biosynthesis.

Objectives Advanced tools and resources are needed to efficiently and sustainably produce food for an increasing world population in the context of variable environmental conditions. The maize genomes to fields (G2F) initiative is a multi-institutional initiative effort that seeks to approach this challenge by developing a flexible and distributed infrastructure addressing emerging problems. G2F has generated large-scale phenotypic, genotypic, and environmental datasets using publicly available inbred lines and hybrids evaluated through a network of collaborators that are part of the G2F’s genotype-by-environment (G × E) project. This report covers the public release of datasets for 2014–2017. Data description Datasets include inbred genotypic information; phenotypic, climatic, and soil measurements and metadata information for each testing location across years. For a subset of inbreds in 2014 and 2015, yield component phenotypes were quantified by image analysis. Data released are accompanied by README descriptions. For genotypic and phenotypic data, both raw data and a version without outliers are reported. For climatic data, a version calibrated to the nearest airport weather station and a version without outliers are reported. The 2014 and 2015 datasets are updated versions from the previously released files [1] while 2016 and 2017 datasets are newly available to the public.

Pre-harvest aflatoxin contamination occurs in maize following kernel colonization by Aspergillus flavus. Aflatoxin contamination resistance is a highly desired trait in maize breeding programs. The identification of novel sources of resistance to pre-harvest aflatoxin contamination is a major focus in germplasm screening efforts. Here, we performed a field evaluation of 64 inbred lines over two years for pre-harvest aflatoxin contamination. Topcrosses were also performed with two testers, B73 and Mo17, to generate 128 F1 hybrids which were also evaluated over two years. Hybrid performance was used to calculate both general combining ability (GCA) of the inbreds, and observed heterosis for aflatoxin resistance. Over both years of the study, aflatoxin concentrations ranged from 80 ± 47 to 17,617 ± 8816 μg kg−1 for inbreds, and from 58 ± 39 to 2771 ± 780 μg kg−1 for hybrids with significant variation between years and lines. The inbred lines CML52, CML69, CML247, GT-603, GEMS-0005, Hi63, Hp301, and M37 W showed

Mycotoxins are toxins produced by fungi which are harmful to humans and animals and can contaminate staple crops. Aflatoxins are particularly toxic and can cause liver cancer so the permitted levels in foodstuffs are legislated. Batches of grain where average aflatoxin concentrations are higher than legislative thresholds are rejected or sold at a lesser price for a more limited range of use. High maximum temperatures and low rainfall have been shown to increase contamination. For corn grown in Southern Georgia, USA, June weather is particularly important as this coincides with the sensitive mid-silk growth stage. An AFs survey and weather data have been used to show the association between AFs and June weather [1]. The risk factors were June maximum temperatures >33˚C and June rainfall 33˚C and rainfall 33˚C and June rainfall

Aspergillus flavus and Aspergillus parasiticus produce carcinogenic aflatoxins during crop infection, with extensive variations in production among isolates, ranging from atoxigenic to highly toxigenic. Here, we report draft genome sequences of one A. parasiticus isolate and nine A. flavus isolates from field environments for use in comparative, functional, and phylogenetic studies.

Corn (Zea mays L.) kernel infection by Aspergillus flavus and subsequent aflatoxin accumulation in grain can have a deleterious effect on both humans and animals that consume contaminated grain. Predicting the aflatoxin risk is challenging due to complex interactions of biotic and abiotic stress factors that govern and exacerbate the phenomenon. The goal of this study was to determine whether a drought index could be used to predict the risk for pre-harvest aflatoxin contamination in corn. Risk assessment was approached at: 1) field (plot) level with data obtained from an in-field controlled experiment (Mississippi study), and 2) state level, where corn fields were sampled at a county level (Georgia study). The data used for this study consisted of historical records on aflatoxin contamination collected over thirteen growing seasons from 2000 to 2011, 2013, and 2014 at Mississippi State, Mississippi (1), and from random corn fields in 53 counties across Georgia between 1977 and 2004 (2). A controlled experiment was conducted at Mississippi with two soil types (a Leeper silty clay loam and a Myatt loam), and three commercial hybrids characterized by different susceptibility levels to aflatoxin contamination. The Agricultural Reference Index for Drought (ARID), a generic drought index for calculating drought on daily basis was evaluated as an aflatoxin risk prediction tool. Mid-silk day was selected to split each growing season into two time periods, which were further divided into positive and negative weeks representing weeks after and before mid-silk, respectively. Weekly ARID factors were calculated for all periods to evaluate the in-season alterations in aflatoxin risk. In both studies, multiple logistic regression models were used to predict aflatoxin risk as a function of the weekly ARID values. In Mississippi, risk level changes were additionally tested according to soil type and corn hybrid aflatoxin susceptibility. The United States Food and Drug Administration restricts corn grain consumption by humans and young animals if the contamination level is above 20 μg/kg; thus, this threshold (20 μg/kg) was selected to develop a binary dependent variable for the logistic model from the raw aflatoxin data. The results revealed that ARID might be used as a predictive tool to assess aflatoxin risk, soil type and hybrid susceptibility to aflatoxin contamination were statistically significant independent factors, and there are critical week windows during the growing season when changes in drought conditions affect the likelihood for aflatoxin contamination. These findings can be used to minimize risk by adapting site-specific management strategies such as triggering irrigation during critical risk weeks, selecting the most appropriate hybrid for a given site/location based on soil type, and determining optimum harvest date.

Remarkable productivity has been achieved in crop species through artificial selection and adaptation to modern agronomic practices. Whether intensive selection has changed the ability of improved cultivars to maintain high productivity across variable environments is unknown. Understanding the genetic control of phenotypic plasticity and genotype by environment (G × E) interaction will enhance crop performance predictions across diverse environments. Here we use data generated from the Genomes to Fields (G2F) Maize G × E project to assess the effect of selection on G × E variation and characterize polymorphisms associated with plasticity. Genomic regions putatively selected during modern temperate maize breeding explain less variability for yield G × E than unselected regions, indicating that improvement by breeding may have reduced G × E of modern temperate cultivars. Trends in genomic position of variants associated with stability reveal fewer genic associations and enrichment of variants 0–5000 base pairs upstream of genes, hypothetically due to control of plasticity by short-range regulatory elements., Breeding has increased crop productivity, but whether it has also changed phenotypic plasticity is unclear. Here, the authors find maize genomic regions selected for high productivity show reduced contribution to genotype by environment variation and provide evidence for regulatory control of phenotypic stability.

Aflatoxin is a mycotoxin produced by the Aspergillus flavus fungi that can severely contaminate corn grain. The U.S. Food and Drug Administration (FDA) have set a limit of 20 ppb, total aflatoxin, for interstate commerce of food and feed as it can induce liver cancer in humans and animals. Contamination is exacerbated by high temperatures, drought conditions and light-textured soil which are all common in Georgia (GA). Lack of irrigation infrastructure can further amplify drought stress and aflatoxin contamination. Accurate aflatoxin assessment requires the collection of multiple corn samples, is expensive and conducted at harvest which does not allow for the use of in-season mitigation strategies to reduce the risk. Given the expense of measurement and the consequences of crop loss, an important goal for agricultural extension services is the prediction and identification of years and counties at higher risk of aflatoxin contamination. This would allow growers to deploy management tactics to reduce risk and to reduce unnecessary expense on aflatoxin testing. In this research, aflatoxin levels were analysed by Poisson kriging and used to validate a strategy for identifying high risk years and counties. It is based on mapping risk factors (Maximum June temperatures, June rainfall, % corn planted area and % soil drainage types) that are above key thresholds. The aflatoxin data used were county level, collected unevenly in space and time from 1977 to 2004 in 53 counties in southern GA. Averaging and typical geostatistical methods were unreliable for producing a temporal summary of the spatial patterns because aflatoxin data were highly skewed and approached a Poisson distribution, and averages for counties with fewer observations are less reliable. Poisson kriging down-weights the influence of these in variogram computation and the estimation process. Comparison tests confirmed significant differences in aflatoxin levels between counties and years that were identified as having different levels of risk using the risk factors approach. Sensitivity analysis for Poisson kriged aflatoxin risk showed that the more years of data are clearly better for this analysis, but fewer than 15 years of data were not advisable.

Aflatoxin is a fungal toxin contaminating corn and causing liver cancer in humans and animals. Contamination is driven by high temperatures and drought. Aflatoxin assessment is expensive so extension services need to identify high risk areas so irrigation, planting strategies and corn varieties can be adapted. This research presents a web-based decision support tool for risk illustrated with a case study from southern Georgia. The tool employs the approach, developed by Kerry et al. (2017b) where exceedance of key thresholds in temperatures, rainfall, soil type and corn production are used to determine risk. The tool also includes NDVI to indicate drought stress and could be further expanded to include new risk factors and adapted to other crops.

Herbicide resistant Palmer amaranth (Amaranthus palmeri) has rapidly become a dominant weed management issue in agronomic crops of the Southeast US. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-biomass, rolled cover crop mulches, in conjunction with herbicide tools. Experiments were conducted to characterize Palmer amaranth suppression and light permeability from a range of rye biomass levels. There was an inverse relationship between Palmer amaranth emergence and rye biomass that was described by a log-logistic regression model. In the absence of rye, there was approximately 80% Palmer amaranth emergence, while the highest rate of rye biomass prevented Palmer amaranth emergence. A log-logistic regression model also described the amount of photosynthetic active radiation transmitted through rye mulch in a green house experiment. The highest level of rye biomass reduced the amount of light to 13% of full sunlight, while 5370 kg ha−1 of rye caused a 50% reduction of light transmission; a similar level of rye biomass (P = 0.93) reduced Palmer amaranth emergence by 50%. Effective suppression of Palmer amaranth will depend upon the ability to produce high-biomass rye. Field experiments evaluated changes in planting date, seeding rate, and nitrogen application on rye biomass production. Maximum rye biomass in April occurred when rye was planted prior to middle-November. However, a 50% reduction in rye biomass resulted from middle-December planting of rye, providing growers with a short planting interval for high-biomass rye production. Additionally, rye seeding rate did not increase rye biomass accumulation indicating that delays in autumn sowing cannot be overcome with plant density. Finally, nitrogen fertilizer applied at planting consistently increased rye biomass production 23–33% relative to non-fertilized controls averaged over all planting dates. Additional research is needed to evaluate how repeated high-biomass cover crop systems affect weed management systems, other pest complexes, and soil moisture status in the sandy soils of the southeast Coastal Plain.

Sugar crops grown for biofuel production provide a source of simple sugars that can readily be made into advanced biofuels. In the mild climate of the southeastern USA, sugar beet can be grown as a winter crop, providing growers with an alternative crop that is complementary to existing summer crops. Experiments evaluated autumn planting dates from September to December on the yield of five varieties of sugar beet harvested in the spring. A linear relationship existed between sugar beet canopy width and thermal time. Plant canopy diameter increased

Worldwide avocado consumption is growing due to potential health benefits. Most research has been focused on ‘Hass’, which does not perform well in Florida. Fatty acids and volatile organic compounds (VOCs) were evaluated in 14 avocado genotypes grown in East-Central Florida conditions and compared to ‘Hass’. Two saturated and five unsaturated fatty acids were detected. Total oil content (TOC) was 11–25%, with 58.2–71.5% unsaturated fatty acids (UFA). ‘FL Hass’ contained 20% TOC, near the average for genotypes tested, but with a low UFA of 61.9%. ‘PA-6206’ (a ‘Hass’ x ‘Bacon’ seedling) and ‘35707’ (a ‘Catalina’ seedling) had higher TOC and UFA than other genotypes, while the mostly West Indian types such as ‘Simmonds’, ‘Day’, ‘Pflume’ and ‘Miguel’ had low TOC. Detected VOCs were acetaldehyde, hexanal, (E)-2-hexenal, limonene, α-cubebene, α-copaene, and β-caryophyllene. Most genotypes contained most of the VOCs. ‘Monroe’ lacked C6 aldehydes, and ‘Pflume’, ‘Bernecker-43’, ‘Lula’ and ‘35707’ lacked some or all sesquiterpenes.

Objectives Crop improvement relies on analysis of phenotypic, genotypic, and environmental data. Given large, well-integrated, multi-year datasets, diverse queries can be made: Which lines perform best in hot, dry environments? Which alleles of specific genes are required for optimal performance in each environment? Such datasets also can be leveraged to predict cultivar performance, even in uncharacterized environments. The maize Genomes to Fields (G2F) Initiative is a multi-institutional organization of scientists working to generate and analyze such datasets from existing, publicly available inbred lines and hybrids. G2F’s genotype by environment project has released 2014 and 2015 datasets to the public, with 2016 and 2017 collected and soon to be made available. Data description Datasets include DNA sequences; traditional phenotype descriptions, as well as detailed ear, cob, and kernel phenotypes quantified by image analysis; weather station measurements; and soil characterizations by site. Data are released as comma separated value spreadsheets accompanied by extensive README text descriptions. For genotypic and phenotypic data, both raw data and a version with outliers removed are reported. For weather data, two versions are reported: a full dataset calibrated against nearby National Weather Service sites and a second calibrated set with outliers and apparent artifacts removed.

Aflatoxin is a carcinogenic toxin to humans and animals produced by mold fungi in staple crops. Surveys of Aflatoxin are expensive, and the results are usually not available for implementing within season mitigation strategies. Identification of high and low risk areas and years is essential to reduce the number of samples analyzed for Aflatoxin concentration. Previously a risk factors approach was developed to determine county level Aflatoxin contamination risk in southern Georgia, but Aflatoxin concentrations and risk factor data were not analyzed simultaneously and all risk factors had equal weight which is unrealistic. In the current paper we propose a regression approach to overcome these problems. Spatial Poisson profile regression identified clusters of counties which have similar Aflatoxin risk and risk factor profiles, whilst explicitly taking into account multicollinearity in the risk factor data and spatial autocorrelation in the Aflatoxin data. This approach allows examination of the utility of different highly correlated variables including remotely sensed data that could give information at the sub-county level. The results identify plausible clusters compared to previous work but also give the relative importance of the risk factors associated with those clusters. The approach also helps show that some factors like well-drained soil behave differently from expectations and irrigation data is not useful.

The colonization of maize (Zea mays L.) and peanut (Arachis hypogaea L.) by the fungal pathogen Aspergillus flavus results in the contamination of kernels with carcinogenic mycotoxins known as aflatoxins leading to economic losses and potential health threats to humans. The regulation of aflatoxin biosynthesis in various Aspergillus spp. has been extensively studied, and has been shown to be related to oxidative stress responses. Given that environmental stresses such as drought and heat stress result in the accumulation of reactive oxygen species (ROS) within host plant tissues, host-derived ROS may play an important role in cross-kingdom communication between host plants and A. flavus. Recent technological advances in plant breeding have provided the tools necessary to study and apply knowledge derived from metabolomic, proteomic, and transcriptomic studies in the context of productive breeding populations. Here, we review the current understanding of the potential roles of environmental stress, ROS, and aflatoxin in the interaction between A. flavus and its host plants, and the current status in molecular breeding and marker discovery for resistance to A. flavus colonization and aflatoxin contamination in maize and peanut. We will also propose future directions and a working model for continuing research efforts linking environmental stress tolerance and aflatoxin contamination resistance in maize and peanut.

Although conservation tillage is widely believed to be an agricultural management practice effective for increasing soil carbon (C) accretion and associated soil quality, there is limited research to determine whether conservation tillage increases net C accretion versus simply altering the distribution of C content by soil depth. We implemented conservation farming practices (winter cover cropping plus strip tillage) for a nonirrigated corn (Zea mays L.) production system in the southeastern coastal plain of Georgia, United States, that had been previously managed under a conventional plow and harrow tillage regime. Total soil C and nitrogen (N) were measured on samples collected from 0 to 65 cm (0 to 25.6 in) at 57 sites before and after five years under conservation farming practices. Crop yield, winter and summer aboveground crop biomass production, and biomass C and N content were also measured annually at each site. Soil C increased an average of 20 Mg ha -1 (8.9 tn ac -1 ; 6 to 62 Mg C ha -1 (2.6 to 27.6 tn C ac -1 ), depending upon slope position) and was associated with a N increase of 2 Mg ha -1 (0.89 tn ac -1 ). Although 72% to 80% of the C accretion was in the top 35 cm (13.8 in), 3 to 6 Mg C ha -1 (1.3 to 2.6 tn C ac -1 ) was accreted from 35 to 65 cm (13.8 to 25.6 in). The soil C accreted during the study amounted to 36% of the net biomass C produced. Corn yield increased 2,200 kg ha -1 (1,964 lb ac -1 ) depending upon slope position (1,200 to 2,500 kg ha -1 (1,071 to 2,232 lb ac -1 )) during the same time. Analysis indicated that soil C content from 15 to 35 cm (5.9 to 13.8 in) was the soil parameter primarily associated with corn yield. Season rainfall from planting to corn silking stage for both corn production years was the lowest in the past 45 years (20 to 25 cm (7.8 to 9.8 in) below the net crop demand) suggesting that soil C-mediated increase in plant-available soil water was a mech- anism contributing to improved corn yield. Calculated estimates (from soil clay, sand, and C content) of increased soil water holding capacity suggest that C accretion in the top 35 cm (13.8 in) of soil potentially increased water storage enough to supply up to four days' worth of additional crop water demand. These results indicated that conservation farming practices can increase soil C and N accretion in degraded sandy soils of the humid southeastern United States coastal plain, and that increased soil C may potentially mitigate the deleterious effects of short-term rainfall deficits in nonirrigated production systems.

Efforts to identify maize germplasm with resistance to Aspergillus flavus infection and subsequent accumulation of aflatoxins were initiated by the US Department of Agriculture, Agricultural Research Service at several locations in the late 1970s and early 1980s. Research units at four locations in the south-eastern USA are currently engaged in identification and development of maize germplasm with resistance to A. flavus infection and accumulation of aflatoxins. The Corn Host Plant Resistance Research Unit, Mississippi State, MS, developed procedures for screening germplasm for resistance to A. flavus infection and accumulation of aflatoxins. Mp313E, released in 1990, was the first line released as a source of resistance to A. flavus infection. Subsequently, germplasm lines Mp420, Mp715, Mp717, Mp718, and Mp719 were released as additional sources of resistance. Quantitative trait loci associated with resistance have also been identified in four bi-parental populations. The Crop Protection and Management Research Unit and Crop Genetics and Breeding Research Unit, Tifton, GA, created a breeding population GT-MAS:gk. GT601, GT602, and GT603 were developed from GT-MAS:gk. The Food and Feed Safety Research Unit, New Orleans, LA, in collaboration with the International Institute for Tropical Agriculture used a kernel screening assay to screen germplasm and develop six germplasm lines with resistance to aflatoxins. The Plant Science Research Unit, Raleigh, NC, through the Germplasm Enhancement of Maize (GEM) Project provides to co-operators diverse germplasm that is a valuable source of resistance to A. flavus infection and accumulation of aflatoxins in maize.

Winter cover crops were evaluated for their effect on Amaranthus palmeri establishment and growth in cotton production. Cover crops examined included rye and four winter legumes: narrow-leaf lupine, crimson clover, Austrian winter pea, and cahaba vetch. Each legume was evaluated alone and in a mixture with rye. Cover crop biomass in monoculture was greatest for rye and lupine (>6750 kg ha−1), while clover, pea, and vetch were less and ranged from 2810 to 4610 kg ha−1. Cover crop biomass was more than doubled when rye was mixed with clover or vetch relative to the legume monoculture. In early-June, A. palmeri densities were 46 seedlings m−2 in the non-disturbed areas between cotton rows in the fallow, while populations were 80% relative to the non-cover crop fallow treatment, while control from clover, vetch and lupine ranged from 64 to 70%. The relationship between A. palmeri control in between cotton rows and cover crop biomass was described by a log-logistic regression model with 4530 kg ha−1 providing median weed control (Bio50); predicted A. palmeri control was 25, 50, and 75% from 2950, 4900, and 8600 kg ha−1 cover crop biomass, respectively. However, A. palmeri plants in the cotton rows prevented yield production in the absence of herbicides. Where A. palmeri was controlled with herbicides, the highest yields occurred following rye, with lower yields following lupin/rye mixture and treatments including pea. Management of herbicide resistant weed species requires diverse management tactics; this may include high-biomass cover crops to reduce weed establishment between crop rows. However, greater research effort is needed to devise weed management options for the crop row that do not rely exclusively on the diminishing array of herbicide tools.

Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize ( Zea mays ) and affecting crop yield and quality. Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides , is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance. The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years. Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg − 1 , while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg − 1 . The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines, particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.

Contamination of crops with aflatoxin is a serious global threat to food safety. Aflatoxin production by Aspergillus flavus is exacerbated by drought stress in the field and by oxidative stress in vitro. We examined transcriptomes of three toxigenic and three atoxigenic isolates of A. flavus in aflatoxin conducive and non-conducive media with varying levels of H2O2 to investigate the relationship of secondary metabolite production, carbon source, and oxidative stress. We found that toxigenic and atoxigenic isolates employ distinct mechanisms to remediate oxidative damage, and that carbon source affected the isolates’ expression profiles. Iron metabolism, monooxygenases, and secondary metabolism appeared to participate in isolate oxidative responses. The results suggest that aflatoxin and aflatrem biosynthesis may remediate oxidative stress by consuming excess oxygen and that kojic acid production may limit iron-mediated, non-enzymatic generation of reactive oxygen species. Together, secondary metabolite production may enhance A. flavus stress tolerance, and may be reduced by enhancing host plant tissue antioxidant capacity though genetic improvement by breeding selection.

Use of novel crops for bio-fuel production requires evaluating the potential for sound ecological and economical implementation in a particular region. We examined the pest and generalist beneficial insect species associated with various winter cover crops (including narrowleaf lupin, white vetch, Austrian winter pea, crimson clover, faba bean, and rye) as sources of colonists in 2 subsequent summer crops, sorghum and cotton. Sorghum is a potential cellulosic bio-fuel crop and cotton is commonly grown in the region and could be a viable low-input rotation for biofuel sorghum. Insects were sampled weekly over 3 ys in winter cover plots beginning in early spring and in the later planted crop plots beginning at the 15 cm height stage of the crops and continuing for 3 - 6 wks. Of the predators, coccinellids (Coleoptera: Coccinellidae) dominated and were consistently abundant in vetch, faba and lupin, as was the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae) and the aphid parasitoid, Lys...

‘Hammock’ (Reg. No. CV-264, PI 652949) centipedegrass [Eremochloa ophiuroides (Munro) Hack] was developed at the Everglades Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Belle Glade, FL and initially approved for release in 2006. A plant patent was fi led in 2008, and U.S. Patent PP20,812 was issued in 2010. Hammock was tested in Florida under the experimental designation of BA-417 and also patented under this name. The purpose of this breeding program was to identify, select, and develop a centipedegrass that would be acceptable as a regional cultivar in the subtropical and tropical climates of Florida. This cultivar originated as an open-pollinated progeny selected and identifi ed as a unique and distinctly different vegetative phenotype growing in a planting of an unimproved population of centipedegrasses typically known throughout the southern U.S. turf industry as common centipedegrass. Hammock was selected for a more compact leaf structure with consistent canopy structure, uniformity, and quality and for its faster rate of crop establishment and ground coverage. Hammock produced leaves that were 13.9% shorter than Centennial and 22.2% shorter than the common centipedegrass standards. It also received signifi cantly higher summerquality ratings, presented acceptable color ratings, and generally produced narrower leaves than the standard cultivars. Hammock established full ground coverage and closed canopy 1 mo earlier than the standard cultivars, but this was site dependent, and differences in seasonal patterns were evident.

Water-deficit stress tolerance is a complex trait, and water deficit results in various physiological and chemical changes in maize (Zea mays L.) and exacerbates pre-harvest aflatoxin contamination. The objective of this study was to characterize the variations in morphology, physiology, and gene expression in two contrasting inbred lines, Lo964 and Lo1016, in order to understand the differences in response to water-deficit stress. The results revealed that Lo964 was less sensitive to water-deficit stress, and had a strong lateral root system and a higher root/shoot ratio in comparison to Lo1016. In response to water-deficit stress by comparing stressed versus well-watered conditions, abscisic acid syntheses were increased in leaves, roots, and kernels of both Lo964 and Lo1016, but by different magnitudes. Indole-3-acetic acid (IAA) was undetectable in the leaves and roots of either genotype regardless of treatments, but increases of 58% and 8% in IAA concentration were observed in 20 DAP kernels, in response to water-deficit stress, respectively. The expression of the MIPS was up-regulated 7-fold in leaf tissues of Lo964 compared to Lo1016 at watered conditions, but decreased significantly to similar levels in both genotypes at water-deficit conditions. ZmPR10 and ZmFer1 expressions tended to up-regulate although ZmPR10 was expressed higher in root tissue while ZmFer1 was expressed higher in leaf tissue. Further study is needed to confirm if Lo964 has reduced aflatoxin contamination associated with the drought tolerance in the field in order to utilize the resistant trait in breeding.

This research examined the expression patterns of 94 stress-related genes in seven maize inbred lines with differential expressions of resistance to aflatoxin contamination. The objective was to develop a set of genes/probes associated with resistance to A. flavus and/or aflatoxin contamination. Ninety four genes were selected from previous gene expression studies with abiotic stress to test the differential expression in maize lines, A638, B73, Lo964, Lo1016, Mo17, Mp313E, and Tex6, using real-time RT-PCR. Based on the relative-expression levels, the seven maize inbred lines clustered into two different groups. One group included B73, Lo1016 and Mo17, which had higher levels of aflatoxin contamination and lower levels of overall gene expression. The second group which included Tex6, Mp313E, Lo964 and A638 had lower levels of aflatoxin contamination and higher overall levels of gene expressions. A total of six “cross-talking” genes were identified between the two groups, which are highly expressed in the resistant Group 2 but down-regulated in susceptible Group 1. When further subjected to drought stress, Tex6 expressed more genes up-regulated and B73 has fewer genes up-regulated. The transcript patterns and interactions measured in these experiments indicate that the resistant mechanism is an interconnected process involving many gene products and transcriptional regulators, as well as various host interactions with environmental factors, particularly, drought and high temperature.

The turf-type bermudagrasses include dip- loid Cynodon transvaalensis Burtt Davy, tetra- ploid C. dactylon (L.) Pers., and sterile triploid hybrids produced by crosses of these species. The objective of this study was to develop a set of microsatellite markers that could distin- guish among commercially important turf-type cultivars. A genomic library enriched for the (CA/GT) n repeat motif was constructed from DNA of the 'Tifway' hybrid and sequenced to identify microsatellite regions. Twenty-fi ve mic- rosatellite-fl anking primer sets were developed and used to genotype two plant introductions and 12 turf-type cultivars. These primer sets produced an average of 10 amplicons across the 14 DNA templates. Sequences of selected amplicons revealed polymorphism resulting from expansion and/or contraction of the micro- satellite and from indel mutations in the micro- satellite fl anking regions. As few as two primer sets were suffi cient to differentiate all unrelated introduction lines and cultivars. The primer sets failed to distinguish among closely related culti- vars developed by selection of natural variants, but one primer set uniquely distinguished the cultivar TifEagle from its irradiated parent cul- tivar. These genomic microsatellites were not derived from gene coding sequences and will supplement the existing expressed sequence tag (EST)-based bermudagrass microsatel- lites. They will be most useful for evaluating the genetic diversity of Cynodon accessions and distinguishing among cultivars that exploit this diversity.

GT603 (Reg. No. GP-577, PI 659665) is an inbred line of yellow dent maize ( Zea mays L.) developed and released in 2010 by the USDA-ARS Crop Protection and Management Research Unit in cooperation with the University of Georgia Coastal Plain Experiment Station. GT603 was developed through seven generations of self-pollination from the maize population GT-MAS:gk (PI 561859), which was released as a source of resistance to Aspergillus fl avus Link:Fr. GT603 was initially selected from early self-pollinated lines under the experimental name GT-P50. Laboratory and fi eld studies demonstrated that GT603 had afl atoxin levels similar to or lower than the related inbred lines GT601 (PI 644026) and GT602 (PI 644027) and the controls Mp313E (PI539859) and Mp715 (PI614819), but it matured earlier than Mp313E and Mp715. The line GT603 is phenotypically different (darker cob and kernel colors and better agronomic traits) from the related lines GT601 and GT602 although the source of resistance may be the same. In hybrid performance tests in 2005 and 2009, GT603 exhibited better combining ability and heterosis with the Stiff Stalk Synthetic (SSS) inbred (B73) than with the non-SSS inbred (Mo17) for afl atoxin level and grain yield.

‘Aloha’ (Reg. No. CV-3, PI 652948) seashore paspalum (Paspalum vaginatum O. Swartz) was developed at the Everglades Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida and jointly released by the Florida and Hawaii agricultural experiment stations. It was initially approved for release in early 2005 and a pending plant patent was submitted in late 2005. This variety of seashore paspalum was selected as an open-pollinated progeny derived from naturalized local landraces growing on the island of Hawaii and was tested in southern Florida under the coded breeding line number H99–47. Aloha was selected for improved agronomic, horticultural, and host-plant resistance traits including a faster rate of crop establishment and ground coverage, darker and deeper green leaf color, and superior resistance to the greenbug aphid (Schizaphis graminum Rondani; Homoptera:Aphididae). In comparison to a set of standard varieties, Aloha attained 50% plot coverage in less than 4 mo whereas the standards took, on average, more than 5 mo. The leaf color of Aloha was a darker green and had a deeper hue than the standard varieties, and the greenbug aphids took longer to reach reproductive maturity, had a shorter lifespan, and produced fewer offspring when cultured on Aloha. Aloha also exhibited a morphology distinct from the standards for a set of measured infl orescence and vegetative traits.

In the Southeastern US, peanut plants are often naturally infected with different viruses resulting in economic losses. Limited information is available concerning the identification and characterization of various viruses in peanut. A collaborative effort has resulted in the production of 44,064 expressed sequence tags (ESTs) from developing seeds at three reproductive stages (R5, R6 and R7) of two peanut genotypes, Tifrunner and GT-C20 and from field collected leaf tissues using the same two genotypes. EST sequences were analyzed, assembled and putative functions were determined based on the comparison of these unique peanut sequences with the National Center of Biotechnology Information (NCBI) non-redundant (nr) database using BLASTX program. Sequences matched viral or viral associated proteins were selected for further study. We analyzed the extent of viral sequences in these peanut ESTs and detected the sequences of Peanut mottle virus (PMV), Peanut stripe virus (PStV) and Tomato spotted wilt virus (TSWV). A total of 942 sequences were identified that matched viral sequences in GenBank to PMV (606), PStV (330) and TSWV (6). We also identified peanut plant sequences with homology to pea (Pisum sativum) plant-specific Potyvirus VPg-interacting protein (PVIP), Arabidopsis thaliana tobamovirus multiplication protein 3 (TOM3) and a tobacco TMV helicase domain-binding protein. These host proteins are essential for viral multiplication and movement from cell to cell in host plants. Further study, we examined and identified the presence of these viral and plant sequences in peanut leaves, seeds and roots using RT-PCR. The potential use of these putative peanut virus host responsive proteins may lead to the development of potentially new strategies to control these virus diseases by silencing or disrupting these genes to prevent virus infection and multiplication in host plants.

Preharvest aflatoxin contamination of grain grown on the US southeastern Coast Plain is provoked and aggravated by abiotic stress. The primary abiotic stress is drought along with high temperatures. The objectives of the present study were to monitor gene expression in developing kernels in response to drought stress and to identify drought-responsive genes for possible use in germplasm assessment. The maize breeding line Tex6 was used, and gene expression profiles were analyzed in developing kernels under drought stress verses well-watered conditions at the stages of 25, 30, 35, 40, 45 d after pollination (DAP) using the 70 mer maize oligo-arrays. A total of 9 573 positive array spots were detected with unique gene IDs, and 7 988 were common in both stressed and well-watered samples. Expression patterns of some genes in several stress response-associated pathways, including abscisic acid, jasmonic acid and phenylalanine ammonia-lyase, were examined, and these specific genes were responsive to drought stress positively. Real-time quantitative polymerase chain reaction validated microarray expression data. The comparison between Tex6 and B73 revealed that there were significant differences in specific gene expression, patterns and levels. Several defense-related genes had been downregulated, even though some defense-related or drought responsive genes were upregulated at the later stages.

The accumulation of aflatoxin, produced by the fungus Aspergillus flavus in maize, is a chronic problem in the southeastern United States. Its presence in grain greatly reduces its value and marketability. Aflatoxin accumulation is frequently associated with high temperatures, drought, and insect damage. Ten maize germplasm lines, some selected for resistance to aflatoxin accumulation, were crossed to transgenic (transformed with genes from Bacillus thuringiensis Berliner (BT) and expressing the Cry1Ab protein) and non-transgenic versions of LH287. Testcrosses were evaluated for ear damage from insect feeding and aflatoxin accumulation. Ear damage caused by insect feeding and aflatoxin accumulation was significantly less in BT than non-BT testcrosses. The germplasm line × BT/non-BT interaction was not significant. Three lines selected for resistance to aflatoxin accumulation (Mp313E, Mp717, Mp04:97) exhibited the lowest levels of aflatoxin whether crossed to the BT or non-BT versions of LH287. Neither the...

Evaluation of corn genotypes for resistance to aflatoxin accumulation has evolved over the past 30 years. Inoculation techniques have been developed to ensure that plants are exposed to Aspergillus flavus and resistant genotypes can be identified. We compared two inoculation techniques (side needle and knife) and different inoculation rates in Georgia and Mississippi. The relative performance of side-needle and knife inoculation techniques did not change or interact significantly across site years, suggesting that both the needle and knife are consistent inoculation techniques for discriminating between resistant and susceptible corn hybrids at the Mississippi State and Tifton locations.

Preharvest aflatoxin contamination of grain grown on the U.S. Southeastern Coastal Plain is provoked and aggravated by both biotic and abiotic stress factors that influence infection by the Asperigillus group. Asperigillus flavus, Link ex Fr., is one of the principal toxigenic fungi of summer grains grown in the region, and the hot, humid weather patterns along with suboptimal summer rainfall favor the development of this organism. An array of arthropod species also contributes to the dispersal of this fungus as they attack and feed on the developing grain. Research on summer grains grown on the Coastal Plain has the expressed goal of reducing, and perhaps eliminating aflatoxin contamination in adapted germplasm using classical crop improvement methods to deploy host plant resistance. This research is complimented and enhanced by molecular techniques that have proven invaluable in the identification and development of superior germplasm. It also emphasizes the need to fully understand the biological inter...

Peanut (Arachis hypogaea L.), or groundnut, is an important crop economically and nutritionally in many tropical and subtropical areas of the world. It is also one of the most susceptible host crops to Aspergillus flavus resulting in aflatoxin contamination. The prevention or elimination of aflatoxin contamination in preharvest and postharvest crops is a serious challenge facing scientists. The recent International Conference on Groundnut Aflatoxin Management and Genomics held in Guangzhou, China, provided an international forum for discussions on the latest accomplishments, the development of strategies, and the initiation of cooperative research for the prevention of aflatoxin contamination. This review summarizes the progress in genetic and genomic research of peanuts and the toxin-producing fungus A. flavus. In particular, the pathway for production and the genetic regulation of afaltoxin, and the peanut-Aspergillus interaction are discussed. The use of a peanut-Aspergillus microarray will help scientists to study the crop-pathogen interaction; aids in the identification of genes involved in both fungal invasion and crop resistance, and ultimately enhance research to find solutions that prevent aflatoxin contamination in agricultural commodities.

Field trials using Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) and Euxesta stigmatias Loew (Diptera: Ulidiidae) were conducted to evaluate resistance and potential damage interactions between these two primary corn, Zea mays L., pests against Lepidoptera-resistant corn varieties derived from both endogenous and exogenous sources. The endogenous source of resistance was maysin, a C-glycosyl flavone produced in high concentrations in varieties 'Zapalote Chico 2451' and 'Zapalote Chico sh2'. The exogenous resistance source was the Bacillus thuringiensis (Bt)11 gene that expresses Cry1A(b) insecticidal protein found in 'Attribute GSS-0966'. Damage by the two pests was compared among these resistant varieties and the susceptible 'Primetime'. Single-species tests determined that the Zapalote Chico varieties and GSS-0966 effectively reduced S. frugiperda larval damage compared with Primetime. E. stigmatias larval damage was less in the Zapalote Chico varieties than the other varieties in single-species tests. E. stigmatias damage was greater on S. frugiperda-infested versus S. frugiperda-excluded ears. Ears with S. frugiperda damage to husk, silk and kernels had greater E. stigmatias damage than ears with less S. frugiperda damage. Reversed phase high-performance liquid chromatography analysis of nonpollinated corn silk collected from field plots determined that isoorientin, maysin, and apimaysin plus 3'-methoxymaysin concentrations followed the order Zapalote Chico sh2 > Zapalote Chico 2451 > Attribute GSS-0966 = Primetime. Chlorogenic acid concentrations were greatest in Zapalote Chico 2451. The two high maysin Zapalote Chico varieties did as well against fall armyworm as the Bt-enhanced GSS-0966, and they outperformed GSS-0966 against E. stigmatias.

Drought stress decreases crop growth, yield, and can further exacerbate pre-harvest aflatoxin contamination. Tolerance and adaptation to drought stress is an important trait of agricultural crops like maize. However, maize genotypes with contrasting drought tolerances have been shown to possess both common and genotype-specific adaptations to cope with drought stress. In this research, the physiological and metabolic response patterns in the leaves of maize seedlings subjected to drought stress were investigated using six maize genotypes including: A638, B73, Grace-E5, Lo964, Lo1016, and Va35. During drought treatments, drought-sensitive maize seedlings displayed more severe symptoms such as chlorosis and wilting, exhibited significant decreases in photosynthetic parameters, and accumulated significantly more reactive oxygen species (ROS) and reactive nitrogen species (RNS) than tolerant genotypes. Sensitive genotypes also showed rapid increases in enzyme activities involved in ROS and RNS metabolism. However, the measured antioxidant enzyme activities were higher in the tolerant genotypes than in the sensitive genotypes in which increased rapidly following drought stress. The results suggest that drought stress causes differential responses to oxidative and nitrosative stress in maize genotypes with tolerant genotypes with slower reaction and less ROS and RNS production than sensitive ones. These differential patterns may be utilized as potential biological markers for use in marker assisted breeding.