Exploring the Mycovirus Sclerotinia sclerotiorum Hypovirulence-Associated DNA Virus 1 as a Biocontrol Agent of White Mold Caused by Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a necrotrophic fungal pathogen causing white mold on many important economic crops. Recently, some mycoviruses such as S. sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) converted S. sclerotiorum into a beneficial symbiont that helps plants manage pathogens and other stresses. To explore the potential use of SsHADV-1 as a biocontrol agent in the United States and to test the efficacy of SsHADV-1-infected United States isolates in managing white mold and other crop diseases, SsHADV-1 was transferred from the Chinese strain DT-8 to United States isolates of S. sclerotiorum. SsHADV-1 is readily transmitted horizontally among United States isolates of S. sclerotiorum and consistently conferred hypovirulence to its host strains. Biopriming of dry bean seeds with hypovirulent S. sclerotiorum strains enhanced resistance to white mold, gray mold, and Rhizoctonia root rot. To investigate the underlying mechanisms, endophytic growth of hypovirulent S. sclerotiorum in dry beans was confirmed using PCR, and the expression of 12 plant defense-related genes were monitored before and after infection. The results indicated that the endophytic growth of SsHADV-1-infected strains in plants stimulated the expression of plant immunity pathway genes that assisted a rapid response from the plant to fungal infection. Finally, application of the seed biopriming technology with SsHADV-1-infected hypervirulent strain has promise for the biological control of several diseases of wheat, pea, and sunflower.

Chickpea Seed Rot and Damping-Off Caused by Metalaxyl-Resistant Pythium ultimum and Its Management with Ethaboxam.

Metalaxyl and its isomer mefenoxam have been the primary fungicides used as seed treatments in managing Pythium seed rot and damping-off of chickpea (Cicer arietinum). However, outbreaks of seed rot and damping-off of metalaxyl-treated chickpea seeds were found in the dryland agriculture regions of southeastern Washington and northern Idaho. Pythium spp. isolated from rotten seeds and associated soils showed high levels of resistance to metalaxyl. Large proportions (31 to 91%) of Pythium isolates resistant to metalaxyl were detected in areas where severe chickpea damping-off occurred and were observed in commercial chickpea fields over several years. All metalaxyl-resistant (MR) isolates were identified as Pythium ultimum var. ultimum. The metalaxyl resistance trait measured by EC50 values was stable over 10 generations in the absence of metalaxyl, and no observable fitness costs were associated with metalaxyl resistance. Under controlled conditions, metalaxyl treatments failed to protect chickpea seeds from seed rot and damping-off after inoculation with MR Pythium isolates. In culture, ethaboxam inhibited mycelial growth of both MR and metalaxyl-sensitive isolates. Greenhouse and field tests showed that ethaboxam is effective in managing MR Pythium. Ethaboxam in combination with metalaxyl is commonly applied as seed treatments in commercial chickpea production.

The D-galacturonic acid catabolic pathway genes differentially regulate virulence and salinity response in Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum causes white mold disease on a wide range of economically important crops such as soybean, canola, tomato, pea and sunflower. As one of the most successful plant pathogens, S. sclerotiorum has the unique ability of adapting to various environmental conditions and effectively suppressing or evading plant defense. Notably, S. sclerotiorum secretes an array of plant cell-wall degrading enzymes (CWDEs) to macerate host cell wall and utilizes the liberated monosaccharides and oligosaccharides as nutrients. One of the major plant cell wall constituents is polygalacturonic acid in pectin, with D-galacturonic acid being the most abundant component. In this research, we identified four S. sclerotiorum genes that encode the enzymes for the D-galacturonic acid catabolism, namely Ssgar1, Ssgar2, Sslgd1 and Sslga1. Gene-knockout mutants were created for all four catabolic genes. When cultured on pectin as the alternative carbon source, Sslgd1- and Sslga1-deletion mutants and Ssgar1/Ssgar2 double deletion mutants exhibited significantly reduced growth. The D-galacturonic acid catabolic genes are transcriptionally induced by either polygalacturonic acid in the culture media or during host infection. Virulence tests of the knockout mutants revealed that Ssgar2, Sslgd1 and Sslga1 all facilitated the effective colonization of S. sclerotiorum to the leaves of soybean and pea, but not of tomato which has the lowest D-galacturonic acid contents in its leaves. In addition to their positive roles in virulence, all four enzymes negatively affect S. sclerotiorum tolerance to salt stress. SsGAR2 has an additional function in tolerance to Congo Red, suggesting a potential role in cell wall stability of S. sclerotiorum. This study is the first report revealing the versatile functions of D-galacturonic acid catabolic genes in S. sclerotiorum virulence, salinity response and cell wall integrity.

Image-Based Phenotyping of Flowering Intensity in Cool-Season Crops.

The timing and duration of flowering are key agronomic traits that are often associated with the ability of a variety to escape abiotic stress such as heat and drought. Flowering information is valuable in both plant breeding and agricultural production management. Visual assessment, the standard protocol used for phenotyping flowering, is a low-throughput and subjective method. In this study, we evaluated multiple imaging sensors (RGB and multiple multispectral cameras), image resolution (proximal/remote sensing at 1.6 to 30 m above ground level/AGL), and image processing (standard and unsupervised learning) techniques in monitoring flowering intensity of four cool-season crops (canola, camelina, chickpea, and pea) to enhance the accuracy and efficiency in quantifying flowering traits. The features (flower area, percentage of flower area with respect to canopy area) extracted from proximal (1.6-2.2 m AGL) RGB and multispectral (with near infrared, green and blue band) image data were strongly correlated (r up to 0.89) with visual rating scores, especially in pea and canola. The features extracted from unmanned aerial vehicle integrated RGB image data (15-30 m AGL) could also accurately detect and quantify large flowers of winter canola (r up to 0.84), spring canola (r up to 0.72), and pea (r up to 0.72), but not camelina or chickpea flowers. When standard image processing using thresholds and unsupervised machine learning such as k-means clustering were utilized for flower detection and feature extraction, the results were comparable. In general, for applicability of imaging for flower detection, it is recommended that the image data resolution (i.e., ground sampling distance) is at least 2-3 times smaller than that of the flower size. Overall, this study demonstrates the feasibility of utilizing imaging for monitoring flowering intensity in multiple varieties of evaluated crops.

Functional Dissection of the Chickpea (Cicer arietinum L.) Stay-Green Phenotype Associated with Molecular Variation at an Ortholog of Mendel's I Gene for Cotyledon Color: Implications for Crop Production and Carotenoid Biofortification.

"Stay-green" crop phenotypes have been shown to impact drought tolerance and nutritional content of several crops. We aimed to genetically describe and functionally dissect the particular stay-green phenomenon found in chickpeas with a green cotyledon color of mature dry seed and investigate its potential use for improvement of chickpea environmental adaptations and nutritional value. We examined 40 stay-green accessions and a set of 29 BC2F4-5 stay-green introgression lines using a stay-green donor parent ICC 16340 and two Indian elite cultivars (KAK2, JGK1) as recurrent parents. Genetic studies of segregating populations indicated that the green cotyledon trait is controlled by a single recessive gene that is invariantly associated with the delayed degreening (extended chlorophyll retention). We found that the chickpea ortholog of Mendel's I locus of garden pea, encoding a SGR protein as very likely to underlie the persistently green cotyledon color phenotype of chickpea. Further sequence characterization of this chickpea ortholog CaStGR1 (CaStGR1, for carietinum stay-green gene 1) revealed the presence of five different molecular variants (alleles), each of which is likely a loss-of-function of the chickpea protein (CaStGR1) involved in chlorophyll catabolism. We tested the wild type and green cotyledon lines for components of adaptations to dry environments and traits linked to agronomic performance in different experimental systems and different levels of water availability. We found that the plant processes linked to disrupted CaStGR1 gene did not functionality affect transpiration efficiency or water usage. Photosynthetic pigments in grains, including provitaminogenic carotenoids important for human nutrition, were 2-3-fold higher in the stay-green type. Agronomic performance did not appear to be correlated with the presence/absence of the stay-green allele. We conclude that allelic variation in chickpea CaStGR1 does not compromise traits linked to environmental adaptation and agronomic performance, and is a promising genetic technology for biofortification of provitaminogenic carotenoids in chickpea.

Production of the antibiotic secondary metabolite solanapyrone A by the fungal plant pathogen Ascochyta rabiei during fruiting body formation in saprobic growth.

Fungi are noted producers of a diverse array of secondary metabolites, many of which are of pharmacological importance. However, the biological roles of the vast majority of these molecules during the fungal life cycle in nature remain elusive. Solanapyrones are polyketide-derived secondary metabolites produced by diverse fungal species including the plant pathogen Ascochyta rabiei. This molecule was originally thought to function as a phytotoxin facilitating pathogenesis of A. rabiei. Chemical profiling and gene expression studies showed that solanapyrone A was specifically produced during saprobic, but not parasitic growth of A. rabiei. Expression of the gene encoding the final enzymatic step in solanapyrone biosynthesis was specifically associated with development of the asexual fruiting bodies of the fungus on certain substrates. In confrontation assays with saprobic fungi that were commonly found in chickpea debris in fields, A. rabiei effectively suppressed the growth of all competing fungi, such as Alternaria, Epicoccum and Ulocladium species. Solanapyrone A was directly detected in the inhibitory zone using a MALDI-imaging mass spectrometry, and the purified compound showed significant antifungal activities against the potential saprobic competitors. These results suggest that solanapyrone A plays an important role for competition and presumably the survival of the fungus.

Comparative Transcriptome Analysis between the Fungal Plant Pathogens Sclerotinia sclerotiorum and S. trifoliorum Using RNA Sequencing.

The fungal plant pathogens Sclerotinia sclerotiorum and S. trifoliorum are morphologically similar, but differ considerably in host range. In an effort to elucidate mechanisms of the host range difference, transcriptomes of the 2 species at vegetative growth stage were compared to gain further insight into commonality and uniqueness in gene expression and pathogenic mechanisms of the 2 closely related pathogens. A total of 23133 and 21043 unique transcripts were obtained from S. sclerotiorum and S. trifoliorum, respectively. Approximately 43% of the transcripts were genes with known functions for both species. Among 1411 orthologous contigs, about 10% (147) were more highly (>3-fold) expressed in S. trifoliorum than in S. sclerotiorum, and about 12% (173) of the orthologs were more highly (>3-fold) expressed in S. sclerotiorum than in S. trifoliorum. The expression levels of genes on the supercontig 30 have the highest correlation coefficient value between the 2 species. Twenty-seven contigs were found to be new and unique for S. trifoliorum. Additionally, differences in expressed genes involved in pathogenesis like oxalate biosynthesis and endopolygalacturonases were detected between the 2 species. The analyses of the transcriptomes not only discovered similarities and uniqueness in gene expression between the 2 closely related species, providing additional information for annotation the S. sclerotiorum genome, but also provided foundation for comparing the transcriptomes with host-infecting transcriptomes.

Functional Analyses of the Diels-Alderase Gene sol5 of Ascochyta rabiei and Alternaria solani Indicate that the Solanapyrone Phytotoxins Are Not Required for Pathogenicity.

Ascochyta rabiei and Alternaria solani, the causal agents of Ascochyta blight of chickpea (Cicer arietinum) and early blight of potato (Solanum tuberosum), respectively, produce a set of phytotoxic compounds including solanapyrones A, B, and C. Although both the phytotoxicity of solanapyrones and their universal production among field isolates have been documented, the role of solanapyrones in pathogenicity is not well understood. Here, we report the functional characterization of the sol5 gene, which encodes a Diels-Alderase that catalyzes the final step of solanapyrone biosynthesis. Deletion of sol5 in both Ascochyta rabiei and Alternaria solani completely prevented production of solanapyrones and led to accumulation of the immediate precursor compound, prosolanapyrone II-diol, which is not toxic to plants. Deletion of sol5 did not negatively affect growth rate or spore production in vitro, and led to overexpression of the other solanapyrone biosynthesis genes, suggesting a possible feedback regulation mechanism. Phytotoxicity tests showed that solanapyrone A is highly toxic to several legume species and Arabidopsis thaliana. Despite the apparent phytotoxicity of solanapyrone A, pathogenicity tests showed that solanapyrone-minus mutants of Ascochyta rabiei and Alternaria solani were equally virulent as their corresponding wild-type progenitors, suggesting that solanapyrones are not required for pathogenicity.

Functional Analyses of the Diels-Alderase Gene sol5 of Ascochyta rabiei and Alternaria solani Indicate that the Solanapyrone Phytotoxins Are Not Required for Pathogenicity.

Ascochyta rabiei and Alternaria solani, the causal agents of Ascochyta blight of chickpea (Cicer arietinum) and early blight of potato (Solanum tuberosum), respectively, produce a set of phytotoxic compounds including solanapyrones A, B, and C. Although both the phytotoxicity of solanapyrones and their universal production among field isolates have been documented, the role of solanapyrones in pathogenicity is not well understood. Here, we report the functional characterization of the sol5 gene, which encodes a Diels-Alderase that catalyzes the final step of solanapyrone biosynthesis. Deletion of sol5 in both Ascochyta rabiei and Alternaria solani completely prevented production of solanapyrones and led to accumulation of the immediate precursor compound, prosolanapyrone II-diol, which is not toxic to plants. Deletion of sol5 did not negatively affect growth rate or spore production in vitro, and led to overexpression of the other solanapyrone biosynthesis genes, suggesting a possible feedback regulation mechanism. Phytotoxicity tests showed that solanapyrone A is highly toxic to several legume species and Arabidopsis thaliana. Despite the apparent phytotoxicity of solanapyrone A, pathogenicity tests showed that solanapyrone-minus mutants of Ascochyta rabiei and Alternaria solani were equally virulent as their corresponding wild-type progenitors, suggesting that solanapyrones are not required for pathogenicity.

A pulse crop dataset of agronomic traits and multispectral images from multiple environments.

Crop yield potential in breeding trials can be captured using unmanned aerial vehicle (UAV) based multispectral imagery. Several digital traits or phenotypes such as vegetation indices can represent canopy crop vigor and overall plant health, which can be used to evaluate differences in performance across varieties in crop breeding programs. This dataset contains agronomic data for named cultivars and breeding lines of spring-sown dry pea and chickpea, and over 275 multispectral images from advanced and preliminary breeding trials. The breeding trials were located at three locations in the "Palouse" region of Eastern Washington and Northern Idaho of the United States across 2017, 2018 and 2019 cropping seasons. The multispectral images were captured using a UAV integrated with a 5-band multispectral camera at multiple time points from early vegetative growth through pod development stages during each cropping season. This dataset details seed yield information from trials of dry peas and chickpea that were obtained from each location, as well as additional agronomic and phenological data recorded at one location (mostly Pullman, WA) for each cropping season. The dataset also includes 20-78 megabytes (MB) Tagged Image Format (TIF) uncalibrated stitched orthomosaic images generated from the photogrammetric software. The images can be processed using any convenient image processing algorithm to obtain vegetation indices and other useful information.

Unraveling the genomic reorganization of polygalacturonase-inhibiting proteins in chickpea.

Polygalacturonase-inhibiting proteins (PGIPs) are cell wall proteins that inhibit pathogen polygalacturonases (PGs). PGIPs, like other defense-related proteins, contain extracellular leucine-rich repeats (eLRRs), which are required for pathogen PG recognition. The importance of these PGIPs in plant defense has been well documented. This study focuses on chickpea (Cicer arietinum) PGIPs (CaPGIPs) owing to the limited information available on this important crop. This study identified two novel CaPGIPs (CaPGIP3 and CaPGIP4) and computationally characterized all four CaPGIPs in the gene family, including the previously reported CaPGIP1 and CaPGIP2. The findings suggest that CaPGIP1, CaPGIP3, and CaPGIP4 proteins possess N-terminal signal peptides, ten LRRs, theoretical molecular mass, and isoelectric points comparable to other legume PGIPs. Phylogenetic analysis and multiple sequence alignment revealed that the CaPGIP1, CaPGIP3, and CaPGIP4 amino acid sequences are similar to the other PGIPs reported in legumes. In addition, several cis-acting elements that are typical of pathogen response, tissue-specific activity, hormone response, and abiotic stress-related are present in the promoters of CaPGIP1, CaPGIP3, and CaPGIP4 genes. Localization experiments showed that CaPGIP1, CaPGIP3, and CaPGIP4 are located in the cell wall or membrane. Transcript levels of CaPGIP1, CaPGIP3, and CaPGIP4 genes analyzed at untreated conditions show varied expression patterns analogous to other defense-related gene families. Interestingly, CaPGIP2 lacked a signal peptide, more than half of the LRRs, and other characteristics of a typical PGIP and subcellular localization indicated it is not located in the cell wall or membrane. The study's findings demonstrate CaPGIP1, CaPGIP3, and CaPGIP4's similarity to other legume PGIPs and suggest they might possess the potential to combat chickpea pathogens.

Fatty acid composition and genome-wide associations of a chickpea (Cicer arietinum L.) diversity panel for biofortification efforts.

Chickpea is a nutritionally dense pulse crop with high levels of protein, carbohydrates, micronutrients and low levels of fats. Chickpea fatty acids are associated with a reduced risk of obesity, blood cholesterol, and cardiovascular diseases in humans. We measured four primary chickpea fatty acids; palmitic acid (PA), linoleic acid (LA), alpha-linolenic acid (ALA), and oleic acid (OA), which are crucial for human health and plant stress responses in a chickpea diversity panel with 256 accessions (Kabuli and desi types). A wide concentration range was found for PA (450.7-912.6 mg/100 g), LA (1605.7-3459.9 mg/100 g), ALA (416.4-864.5 mg/100 g), and OA (1035.5-1907.2 mg/100 g). The percent recommended daily allowances also varied for PA (3.3-6.8%), LA (21.4-46.1%), ALA (34.7-72%), and OA (4.3-7.9%). Weak correlations were found among fatty acids. Genome-wide association studies (GWAS) were conducted using genotyping-by-sequencing data. Five significant single nucleotide polymorphisms (SNPs) were identified for PA. Admixture population structure analysis revealed seven subpopulations based on ancestral diversity in this panel. This is the first reported study to characterize fatty acid profiles across a chickpea diversity panel and perform GWAS to detect associations between genetic markers and concentrations of selected fatty acids. These findings demonstrate biofortification of chickpea fatty acids is possible using conventional and genomic breeding techniques, to develop superior cultivars with better fatty acid profiles for improved human health and plant stress responses.

Links among nitrification, nitrifier communities, and edaphic properties in contrasting soils receiving dairy slurry.

Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy (Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha(-1). Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties.

Linkage QTL Mapping and Genome-Wide Association Study on Resistance in Chickpea to Pythium ultimum.

The soilborne oomycete plant pathogen Pythium ultimum causes seed rot and pre-emergence damping-off of chickpea (Cicer arietinum L.). The pathogen has been controlled for several decades using the fungicide metalaxyl as seed treatment but has re-emerged as a severe problem with the detection of metalaxyl-resistant isolates of the pathogen from infested fields in the United States Pacific Northwest. The objective of this study was to identify genetic markers and candidate genes associated with resistance to P. ultimum in an interspecific recombinant inbred line population (CRIL-7) derived from a cross between C. reticulatum (PI 599072) x C. arietinum (FLIP 84-92C) and conduct genome-wide association studies (GWAS) for disease resistance using a chickpea diversity panel consisting of 184 accessions. CRIL-7 was examined using 1029 SNP markers spanning eight linkage groups. A major QTL, "qpsd4-1," was detected on LG 4 that explained 41.8% of phenotypic variance, and a minor QTL, "qpsd8-1," was detected on LG8 that explained 4.5% of phenotypic variance. Seven candidate genes were also detected using composite interval mapping including several genes previously associated with disease resistance in other crop species. A total of 302,902 single nucleotide polymorphic (SNP) markers were used to determine population structure and kinship of the diversity panel. Marker-trait associations were established by employing different combinations of principal components (PC) and kinships (K) in the FarmCPU model. Genome-wide association studies detected 11 significant SNPs and seven candidate genes associated with disease resistance. SNP Ca4_1765418, detected by GWAS on chromosome 4, was located within QTL qpsd4-1 that was revealed in the interspecific CRIL-7 population. The present study provides tools to enable MAS for resistance to P. ultimum and identified genomic domains and candidate genes involved in the resistance of chickpea to soilborne diseases.

Genome Sequence of Sclerotinia sclerotiorum Hypovirulence-Associated DNA Virus 1 Found in the Fungus Penicillium olsonii Isolated from Washington State, USA.

We report the discovery of a Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) isolate, named SsHADV1_PO, from the fungus Penicillium olsonii isolated from Washington state, USA. The genome of SsHADV1_PO is 2,166 bp and contains two open reading frames, with more than 98% nucleotide identity with respect to reported SsHADV-1 isolates.

A fungal extracellular effector inactivates plant polygalacturonase-inhibiting protein.

Plant pathogens degrade cell wall through secreted polygalacturonases (PGs) during infection. Plants counteract the PGs by producing PG-inhibiting proteins (PGIPs) for protection, reversibly binding fungal PGs, and mitigating their hydrolytic activities. To date, how fungal pathogens specifically overcome PGIP inhibition is unknown. Here, we report an effector, Sclerotinia sclerotiorum PGIP-INactivating Effector 1 (SsPINE1), which directly interacts with and functionally inactivates PGIP. S. sclerotiorum is a necrotrophic fungus that causes stem rot diseases on more than 600 plant species with tissue maceration being the most prominent symptom. SsPINE1 enhances S. sclerotiorum necrotrophic virulence by specifically interacting with host PGIPs to negate their polygalacturonase-inhibiting function via enhanced dissociation of PGIPs from PGs. Targeted deletion of SsPINE1 reduces the fungal virulence. Ectopic expression of SsPINE1 in plant reduces its resistance against S. sclerotiorum. Functional and genomic analyses reveal a conserved virulence mechanism of cognate PINE1 proteins in broad host range necrotrophic fungal pathogens.

Crop Performance Evaluation of Chickpea and Dry Pea Breeding Lines Across Seasons and Locations Using Phenomics Data.

The Pacific Northwest is an important pulse production region in the United States. Currently, pulse crop (chickpea, lentil, and dry pea) breeders rely on traditional phenotyping approaches to collect performance and agronomic data to support decision making. Traditional phenotyping poses constraints on data availability (e.g., number of locations and frequency of data acquisition) and throughput. In this study, phenomics technologies were applied to evaluate the performance and agronomic traits in two pulse (chickpea and dry pea) breeding programs using data acquired over multiple seasons and locations. An unmanned aerial vehicle-based multispectral imaging system was employed to acquire image data of chickpea and dry pea advanced yield trials from three locations during 2017-2019. The images were analyzed semi-automatically with custom image processing algorithm and features were extracted, such as canopy area and summary statistics associated with vegetation indices. The study demonstrated significant correlations (P < 0.05) between image-based features (e.g., canopy area and sum normalized difference vegetation index) with yield (r up to 0.93 and 0.85 for chickpea and dry pea, respectively), days to 50% flowering (r up to 0.76 and 0.85, respectively), and days to physiological maturity (r up to 0.58 and 0.84, respectively). Using image-based features as predictors, seed yield was estimated using least absolute shrinkage and selection operator regression models, during which, coefficients of determination as high as 0.91 and 0.80 during model testing for chickpea and dry pea, respectively, were achieved. The study demonstrated the feasibility to monitor agronomic traits and predict seed yield in chickpea and dry pea breeding trials across multiple locations and seasons using phenomics tools. Phenomics technologies can assist plant breeders to evaluate the performance of breeding materials more efficiently and accelerate breeding programs.

Chickpea (Cicer arietinum L.) as a Source of Essential Fatty Acids - A Biofortification Approach.

Chickpea is a highly nutritious pulse crop with low digestible carbohydrates (40-60%), protein (15-22%), essential fats (4-8%), and a range of minerals and vitamins. The fatty acid composition of the seed adds value because fats govern the texture, shelf-life, flavor, aroma, and nutritional composition of chickpea-based food products. Therefore, the biofortification of essential fatty acids has become a nutritional breeding target for chickpea crop improvement programs worldwide. This paper examines global chickpea production, focusing on plant lipids, their functions, and their benefits to human health. In addition, this paper also reviews the chemical analysis of essential fatty acids and possible breeding targets to enrich essential fatty acids in chickpea (Cicer arietinum) biofortification. Biofortification of chickpea for essential fatty acids within safe levels will improve human health and support food processing to retain the quality and flavor of chickpea-based food products. Essential fatty acid biofortification is possible by phenotyping diverse chickpea germplasm over suitable locations and years and identifying the candidate genes responsible for quantitative trait loci mapping using genome-wide association mapping.

Development and characterization of microsatellite markers of the fungal plant pathogen Sclerotinia trifoliorum.

Sclerotinia trifoliorum is an important pathogen of forage legumes and some grain legumes. Attempts to study its population biology using microsatellite markers developed for Sclerotinia sclerotiorum and Sclerotinia subarctica resulted in no amplification or low levels of polymorphism. This study reports the development and characterization of 33 microsatellite loci developed from a microsatellite-enriched library of S. trifoliorum. Based on a population of 42 isolates of S. trifoliorum, these microsatellite markers are highly polymorphic, with a mean of 6.5 alleles per locus (range 3-12) and a mean expected heterozygosity of 0.63 (range 0.26-0.9). Based on locations of these marker sequences in the S. sclerotiorum genome, these microsatellite loci are dispersed throughout the genome. However, 50% (265 of 528) of pairwise comparisons of the 33 microsatellite loci had significant linkage disequilibrium, which could be explained by the mixed mating systems (homothallism and heterothallism) and clonal reproduction of S. trifoliorum. Thirty of the 33 loci were successfully applied to S. sclerotiorum, and 28 loci were polymorphic. However, only 10 loci are applicable to Sclerotinia minor and 1 locus to Sclerotinia homoeocarpa. These markers are therefore useful for population structure assessment, QTL mapping, and ecological analyses in S. trifoliorum and potentially in other Sclerotinia species.

Genotype and Environment Effects on Prebiotic Carbohydrate Concentrations in Kabuli Chickpea Cultivars and Breeding Lines Grown in the U.S. Pacific Northwest.

Prebiotic carbohydrates are compounds that include simple sugars, sugar alcohols, and raffinose family oligosaccharides, which are fermented by gut bacteria and can influence the species profile of the gut microbiome to reduce obesity and weight gain. Prebiotic carbohydrates are also associated with several health benefits including reduced insulin dependence and incidence of colorectal cancer. Although pulse crops such as chickpea have been important sources of nutrition for human diets for thousands of years, relatively little is known about the profiles of prebiotic carbohydrates in pulse crops. The objectives of this study were to characterize the type and concentration of seed prebiotic carbohydrates in 18 kabuli chickpea genotypes grown in 2017 and 2018 in Idaho and Washington, and partition variance components conditioning these nutritional quality traits in chickpea. Genotype effects were significant for fructose, sucrose, raffinose, and kestose. Environment effects were also significant for several carbohydrates. However, year effects were the greatest sources of variance for all carbohydrates. Concentrations of most carbohydrates were significantly greater in 2017, when there was less precipitation during the growing season coupled with greater heat stress during grain filling than in 2018. This may reflect the role of many of these carbohydrates as osmoprotectants produced in response to heat and water stress. Overall, our results suggest that a survey of more genetically diverse plant materials, such as a chickpea 'mini-core' collection, may reveal genotypes that produce significantly greater concentrations of selected prebiotic carbohydrates and could be used to introduce desirable nutritional traits into adapted chickpea cultivars.