Crops are hosts to numerous plant pathogenic microorganisms. Maize has several major disease issues; thus, breeding multiple disease resistant (MDR) varieties is critical. While the genetic basis of resistance to multiple fungal pathogens has been studied in maize, less is known about the relationship between fungal and bacterial resistance. In this study, we evaluated a disease resistance introgression line (DRIL) population for the foliar disease Goss's bacterial wilt and blight (GW) and conducted quantitative trait locus (QTL) mapping. We identified a total of ten QTL across multiple environments. We then combined our GW data with data on four additional foliar diseases (northern corn leaf blight, southern corn leaf blight, gray leaf spot, and bacterial leaf streak) and conducted multivariate analysis to identify regions conferring resistance to multiple diseases. We identified 20 chromosomal bins with putative multiple disease effects. We examined the five chromosomal regions (bin 1.05, 3.04, 4.06, 8.03, and 9.02) with the strongest statistical support. By examining how each haplotype effected each disease, we identified several regions associated with increased resistance to multiple diseases and three regions associated with opposite effects for bacterial and fungal diseases. In summary, we identified several promising candidate regions for multiple disease resistance in maize and specific DRILs to expedite interrogation.

Background: Exserohilum turcicum is an important pathogen of both sorghum and maize, causing sorghum leaf blight and northern corn leaf blight. Because the same pathogen can infect and cause major losses for two of the most important grain crops, it is an ideal pathosystem to study plant-pathogen evolution and investigate shared resistance mechanisms between the two plant species. To identify sorghum genes involved in the E. turcicum response, we conducted a genome-wide association study (GWAS). Results: Using the sorghum conversion panel evaluated across three environments, we identified a total of 216 significant markers. Based on physical linkage with the significant markers, we detected a total of 113 unique candidate genes, some with known roles in plant defense. Also, we compared maize genes known to play a role in resistance to E. turcicum with the association mapping results and found evidence of genes conferring resistance in both crops, providing evidence of shared resistance between maize and sorghum. Conclusions: Using a genetics approach, we identified shared genetic regions conferring resistance to E. turcicum in both maize and sorghum. We identified several promising candidate genes for resistance to leaf blight in sorghum, including genes related to R-gene mediated resistance. We present significant advancements in the understanding of host resistance to E. turcicum, which is crucial to reduce losses due to this important pathogen.

Miscanthus is a genus of perennial, warm season grasses that is a leading candidate for biomass production in temperate environments. Relative to other C4 grasses, some Miscanthus genotypes have exceptionally efficient photosynthesis at low temperatures. Typically planted at about the same time as maize (Zea mays L.), it is unknown if earlier planting of Miscanthus would be possible or even preferable. Moreover, little is known about the response of Miscanthus to frosts. The aim of this study was to determine low temperature thresholds for damage and death of Miscanthus seedlings in a controlled environment chamber, quantify the effect of early planting dates for Miscanthus seedlings in the field on survival, growth, and yield, and assess genotypic differences for spring and autumn frost tolerance for field plantings of established clonal materials. We observed that Miscanthus seedlings and mature plants had exceptional cold tolerance for a C4 grass. In a controlled environment chamber, 29 to 65% of seedlings in four Miscanthus populations subjected to a 12 h cold treatment at −10°C survived, whereas none of the maize seedlings survived a 1°C treatment. In the field, all Miscanthus seedling populations tested had ≥66% survival in 2011 and 2012, despite light freezes associated with planting in mid‐March at Urbana, IL. The standard for biomass production, M. ×giganteus J. M. Greef & Deuter ex Hodk. & Renvoize, had low frost tolerance relative to other genotypes, indicating potential for genetic improvement.

Miscanthus is among the best biomass crops for temperate environments but current production is almost entirely associated with a single sterile clone of Miscanthus × giganteus J.M.Greef, Deuter ex Hodk., Renvoize. To create additional and improved cultivars, characterization of available germplasm is needed for biomass traits and genotype × environment (G × E) interactions. Additionally, there has been little guidance on how to best allocate experimental units in Miscanthus breeding trials. The purpose of this study was to quantify genetic diversity for biomass yield in a Miscanthus germplasm collection of 98 accessions that represent publicly available materials in North America, determine the predictive value of three putative yield component traits for estimating yield, and quantify the relative importance of G × E and error variances for estimating genotypic values. We observed large and significant differences among genotypes for all traits. Indirect selection for yield based on the tested yield‐component traits alone would be too inefficient to be advisable. Estimates of G × E interactions and repeatabilities indicated that selection efficiency would benefit more from increased sampling of locations rather than years and that effective selection of Miscanthus for yield could be accomplished in Year 2 rather than Year 3 for environments similar to central and southern Illinois. Minimizing the number of years per selection cycle will be critical for maximizing genetic gain per unit of time.

Bacterial leaf streak (BLS), a foliar disease of maize (Zea mays L.) caused by Xanthomonas vasicola pv. vasculorum, recently emerged in the Americas as a disease of major importance. Little is known about the disease cycle, and consequently, management is difficult. No chemical control is available. Host resistance will likely play a major role in controlling the disease, but to date, no data regarding the resistance of maize germplasm to X. vasicola pv. vasculorum have been published. The objective of this study was to examine the genetic architecture of resistance to BLS. We conducted quantitative trait locus (QTL) mapping for BLS resistance in three maize populations: the Z022 (B73 × Oh43 recombinant inbred line) nested association mapping (NAM) population, the Z023 (B73 × Oh7B recombinant inbred line) NAM population, and the DRIL78 (NC344 × Oh7B chromosome segment substitution line) population. A total of five QTL were detected across two of the mapping populations. Of the QTL detected, one conferred a moderate effect, whereas the others conferred small effects. We also examined the relationship between resistance to BLS and resistance to three foliar diseases of maize, which had been mapped previously. The only significant correlation we found for BLS was with northern corn leaf blight [caused by Exserohilum turcicum (Pass.) K. J. Leonard & Suggs] in one of the populations, although two of the five BLS regions were involved in resistance to other diseases. These data will be useful for developing maize varieties resistant to BLS to mitigate the impact of bacterial leaf streak on maize production.