Abstract
Among various foliar diseases affecting maize yields worldwide, northern corn leaf blight (NCLB) is economically important. The genetics of resistance was worked out to be quantitative in nature thereby suggesting the need for the detection of quantitative trait loci (QTL) to initiate effective marker-aided breeding strategies. From the cross CML153 (susceptible) × SKV50 (resistant), 344 F2:3 progenies were derived and screened for their reaction to NCLB during the rainy season of 2013 and 2014. The identification of QTL affecting resistance to NCLB was carried out using the genetic linkage map constructed with 194 polymorphic SNPs and the disease data recorded on F2:3 progeny families. Three QTL for NCLB resistance were detected on chromosomes 2, 5, and 8 with the QTL qNCLB-8-2 explaining the highest phenotypic variation of 16.34% followed by qNCLB-5 with 10.24%. QTL for resistance to sorghum downy mildew (SDM) and southern corn rust (SCR) were also identified from one season phenotypic data, and the co-location of QTL for resistance to three foliar diseases was investigated. QTL present in chromosome bins 8.03, 5.03, 5.04, and 3.04 for resistance to NCLB, SDM, and SCR were co-localized, indicating their usefulness for the pyramiding of quantitative resistance to multiple foliar pathogens. Marker-assisted selection was practiced in the crosses CM212 × SKV50, HKI162 × SKV50, and CML153 × SKV50 employing markers linked to major QTL on chromosomes 8, 2, and 10 for NCLB, SDM, and SCR resistance, respectively. The populations were advanced to F6 stage to derive multiple disease-resistant inbred lines. Out of the 125 lines developed, 77 lines were tested for their combining ability and 39 inbred lines exhibited high general combining ability with an acceptable level of resistance to major diseases.
Highlights
Maize (Zea mays L.) is a widely cultivated food crop worldwide along with rice and wheat
Northern corn leaf blight incited by Exserohilum turcicum (Pass) Leonard and Suggs (Teliomorph = Setosphaeria turcica (Luttrell), sorghum downy mildew caused by Peronosclerospora sorghi (Weston and Uppal), and southern corn rust caused by Puccinia polysora (Underwood) are considered as the most persistent and destructive diseases of field maize (Pratt and Gordon, 2006)
Weather conditions at Mandya favored the development of severe northern corn leaf blight disease
Summary
Maize (Zea mays L.) is a widely cultivated food crop worldwide along with rice and wheat. It serves as a livestock feed and industrial raw material (Troyer, 2006). Maize (Z. mays L.) is cultivated in a wide variety of environments with major cultivation in the warmer parts of temperate regions and in humid–subtropical climate (Dowswell et al, 1996). About 61 diseases have been recorded on maize in India causing yield losses (Payak et al, 1973; Payak and Sharma, 1985).
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