Southern Leaf Blight, Northern Leaf Blight, and Gray Leaf Spot, caused by ascomycete fungi, are among the most important foliar diseases of maize worldwide. Previously, disease resistance quantitative trait loci (QTL) for all three diseases were identified in a connected set of chromosome segment substitution line (CSSL) populations designed for the identification of disease resistance QTL. Some QTL for different diseases co-localized, indicating the presence of multiple disease resistance (MDR) QTL. The goal of this study was to perform an independent test of several of the MDR QTL identified to confirm their existence and derive a more precise estimate of allele additive and dominance effects. Twelve F 2:3 family populations were produced, in which selected QTL were segregating in an otherwise uniform genetic background. The populations were assessed for each of the three diseases in replicated trials and genotyped with markers previously associated with disease resistance. Pairwise phenotypic correlations across all the populations for resistance to the three diseases ranged from 0.2 to 0.3 and were all significant at the alpha level of 0.01. Of the 44 QTL tested, 16 were validated (identified at the same genomic location for the same disease or diseases) and several novel QTL/disease associations were found. Two MDR QTL were associated with resistance to all three diseases. This study identifies several potentially important MDR QTL and demonstrates the importance of independently evaluating QTL effects following their initial identification.

Calcium (Ca) is an essential plant nutrient, required for signaling, cell wall fortification and growth and development. Calcium deficiency (Ca-deficiency) in maize causes leaf tip rot and a so-called “bull-whipping” or “buggy-whipping” phenotype. Seedlings of the maize line B73 displayed these Ca-deficiency-like symptoms when grown in the greenhouse with excess fertilizer during the winter months, while seedlings of the Mo17 maize line did not display these symptoms under the same conditions. These differential phenotypes could be recapitulated in ‘mini-hydroponic’ systems in the laboratory in which high ammonium, but not nitrate, levels induced the symptoms in B73 but not Mo17 seedlings. Consistent with this phenotype being caused by Ca-deficiency, addition of Ca2+ completely relieved the symptoms. These data suggest that ammonium reduces the seedling’s ability to absorb calcium, which causes the Ca-deficiency phenotype, and that this trait varies among genotypes. A recombinant inbred line (RIL) population derived from a B73 x Mo17 cross was used to map quantitative trait loci (QTL) associated with the Ca-deficiency phenotype. QTL associated with variation in susceptibility to Ca-deficiency were detected on chromosomes 1, 2, 3, 6 which explained between 3.30–9.94% of the observed variation. Several genes predicted to bind or be activated by calcium map to these QTL on chromosome 1, 2, 6. These results describe for the first time the genetics of Ca-deficiency symptoms in maize and in plants in general.

Peas (Pisum sativum) are the second most cultivated pulse crop in the world. They can serve as human food, fodder, and cover crop. The most serious foliar disease of pea cultivars worldwide is Ascochyta blight, which can be caused by several pathogens. Of these, Peyronella pinodes is the most aggressive and prevalent worldwide. Several traits, including resistance to Peyronella pinodes, stem diameter, internode length between nodes 2-3 and 5-6, and area of 7th leaf were measured in 269 entries of the Pea Single Plant Plus Collection (SPPC). The heritability (H2) of the morphological traits was relatively high, while disease resistance had low heritability. Using 53,196 single nucleotide polymorphism (SNPs) markers to perform a genome-wide association study to identify genomic loci associated with variation in all the traits measured, we identified 27 trait-locus associations, 5 of which were associated with more than one trait.

Winter pea (Pisum sativum L.) can be used as a forage and cover crop in the southeast and mid-Atlantic United states; however, minimal effort has been devoted to optimize winter pea genetics for forage and cover crop production in these regions. Studies were conducted from 2015-2017 in Maryland and North Carolina screening 18 winter pea genotypes for forage and cover crop use. Winter pea genotypes were compared with widely grown crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth]. All legume genotypes were harvested across four timings. Legume winter hardiness, disease incidence, biomass production, quality, and N release were estimated. Winter hardiness was severe with many winter pea genotypes at the Maryland environments, which restricted winter pea biomass production. There was considerable variation for disease incidence among the winter pea genotypes depending on biotic stressors at each environment. At the North Carolina environments, several winter pea genotypes produced similar biomass to crimson clover and hairy vetch across harvest timings. At the Maryland environments, crimson clover and hairy vetch biomass exceeded winter pea biomass. The winter pea genotypes varied considerably for quality traits including protein, lignin, and cellulose. Relative forage value declined as biomass harvest was delayed and was generally higher with all winter pea genotypes than crimson clover or hairy vetch. These results show wide genetic variation in the winter pea genotypes screened for biomass and quality; this variation could be utilized in breeding efforts to enhance winter pea production in the region. 1 INTRODUCTION Cover crop adoption is increasing in the U.S. southeast region, with some states having surpassed 10% of cropland acreage planted with cover crops (USDA-National Agricultural Statistics Service, 2016; Wayman et al., 2016). Farm-Abbreviations: ADF, acid detergent fiber; NDF, neutral detergent fiber; NIRS, near-infrared spectroscopy; RFV, relative forage value.