Quantitative trait loci mapping for Gibberella ear rot resistance and associated agronomic traits using genotyping-by-sequencing in maize

Abstract

Unique and co-localized chromosomal regions affecting Gibberella ear rot disease resistance and correlated agronomic traits were identified in maize. Dissecting the mechanisms underlying resistance to Gibberella ear rot (GER) disease in maize provides insight towards more informed breeding. To this goal, we evaluated 410 recombinant inbred lines (RIL) for GER resistance over three testing years using silk channel and kernel inoculation techniques. RILs were also evaluated for agronomic traits like days to silking, husk cover, and kernel drydown rate. The RILs showed significant genotypic differences for all traits with above average to high heritability estimates. Significant (P < 0.01) but weak genotypic correlations were observed between disease severity and agronomic traits, indicating the involvement of agronomic traits in disease resistance. Common QTLs were detected for GER resistance and kernel drydown rate, suggesting the existence of pleiotropic genes that could be exploited to improve both traits at the same time. The QTLs identified for silk and kernel resistance shared some common regions on chromosomes 1, 2, and 8 and also had some regions specific to each tissue on chromosomes 9 and 10. Thus, effective GER resistance breeding could be achieved by considering screening methods that allow exploitation of tissue-specific disease resistance mechanisms and include kernel drydown rate either in an index or as indirect selection criterion.

QTL mapping and candidate genes for resistance to Fusarium ear rot and fumonisin contamination in maize

“…The parental lines employed in the present study were initially selected for F. graminearum resistance, but showed analogous levels of resistance to FER and common smut ( Ustilago zeae ) [42]. Indeed, a cross with parent CO441 was recently used to detect QTLs related to GER resistance [45]. Resistant sources to multiple maize pathogens, such as F. verticillioides , F. graminearum and A. flavus were found, suggesting the presence of a common genetic mechanism regulating resistance to different diseases [6, 10, 13].…”

“…Furthermore, SNPs associated with resistance to GER in a CO441xB73 RIL population were located close to qFER-1/qFB1-1.1, qFER-2.2, qFB1-9.1 and qFER-9.3/qFB1-9.3 [45]. Similarly, qFB1-1.3, qFB1-4.1, qFER-9.1 and qFB1-9.2 localized in bin positions corresponding to QTLs for GER resistance, ZEA and DON contamination reduction [39, 40].…”

Ethylene signaling regulates natural variation in the abundance of antifungal acetylated diferuloylsucroses and Fusarium graminearum resistance in maize seedling roots

“…Depending on the developmental stage and infection site, F. graminearum also can cause root rot, stem rot and ear rot in maize (Munkvold & White, 2016). Previous research on maize-F. graminearum interactions has focused primarily on ear rot, with results generally showing that resistance against this disease is controlled by numerous small-effect quantitative trait loci (QTL) that are influenced by experimental methods and genetic backgrounds (Ali et al, 2005;Kebede et al, 2016;Brauner et al, 2017). Furthermore, transcriptomic studies in maize and wheat show that host-F. graminearum interactions are significantly influenced by host tissue types, suggesting that the QTL associated with F. graminearum ear rot resistance probably will not confer resistance in seedling roots (Kazan et al, 2012;Zhang et al, 2016).…”

Fusarium graminearum-induced shoot elongation and root reduction in maize seedlings correlate with later seedling blight severity

“…Genetic mapping of Gibberella ear rot resistance based on symptom severity has identified a large number of quantitative trait loci (QTL), each with small effect size. Moreover, these QTL tend to be sensitive to experimental methods and environmental conditions, making them difficult to validate across different studies (Ali et al 2005; Brauner et al 2017; Kebede et al 2016). In contrast, major genetic loci contributing to Gibberella stalk rot resistance have been identified with bi-parental mapping populations (Chen et al 2017; Ma et al 2017; Yang et al 2010; Zhang et al 2012).…”