Mapping of QTL Conferring Resistance to Turcicum Leaf Blight using Microsatellites in Maize (Zea mays L.)

Abstract

Turcicum Leaf Blight (TLB), caused by Exserohilum turcicum is a foliar disease of maize. This study was conducted to identify quantitative trait loci (QTL) for TLB resistance in maize. A mapping population constituting 185 F_2:3 populations was developed by crossing two inbred lines viz., CM 212 (susceptible) and V 336 (resistant), and was evaluated in two environments to generate phenotypic data for QTL mapping. A polymorphic survey of 183 pairs of simple sequence repeat (SSR) primers between the two parents helped in identification of 101 polymorphic markers. Data on four disease severity traits viz., Percent Disease Index (PDI), Area Under Disease Progress Curve based on PDI (AUDPC-PDI), Lesion Area (LA), and Area Under Disease Progress Curve based on LA (AUDPC-LA) were generated for QTL mapping. Eight QTL intervals for resistance to TLB were located on chromosomes 2, 3, 4, 5, 7 and 9. Out of the eight QTL; one QTL was reported for LA on chromosome 4 flanking phi019 and bnlg2162 markers at the low disease-pressure environment (E₁), six QTL at high disease-pressure environment (E₂) and one QTL across pooled environments. Out of the six QTL identified at high disease-pressure environment, one QTL for AUDPC-PDI was identified on chromosome 9 flanked by markers phi065 and phi016 while the remaining five QTL for LA were identified on chromosomes 2, 3, 5 and 7. One QTL for PDI was identified across environments analysis on chromosome 3 flanked by markers mmc0071 and bnlg1160. For these QTL, the LOD values ranged from 2.70 to 14.84 and corresponding R² (% variation explained) ranged from 12.96 to 18.98 % in the individual environments. All QTL showed overdominance gene action except QTL 4 (dominance) at their respective chromosome.