To identify genetic variability for resistance to banded leaf and sheath blight (BLSB) in India, 29 selected inbred lines were evaluated under artificial inoculation at three disease hot spots (Udaipur, Pantnagar and New Delhi, India) during the kharif (monsoon) seasons of 2002-2004. The study indicated high vulnerability of the maize lines to the BLSB isolates; only one inbred line (CA00106) offered moderate resistance to BLSB at all three locations, while some (eg, CM104 and LM6) showed moderate resistance at specific locations. To analyze the genetic basis of resistance to BLSB, a half-diallel set was generated using nine inbred lines (CA00106, CA00310, CM104, CM105, CM300, CM139, CM140, LM5 and LM6) differing in their responses to BLSB. Evaluation of this set at Delhi, Pantnagar and Udaipur revealed larger SCA effects as compared to GCA effects, and a significant contribution of nonadditive gene action. The combining ability analyses indicated that BLSB resistance was both generally and specifically transferable among crosses. An F2:3 mapping population comprising 193 individuals was generated using CA00106 as the resistant parent and CM140 as the susceptible parent. Genotyping of this mapping population was undertaken using 127 polymorphic SSR (single sequence repeat) markers covering the maize genome. Linkage mapping was performed with the MULTIPOINT software using genotypic data from 108 SSR markers. The map had a total length of 2001.3 cM, with an average marker interval of 19.53 cM. Phenotyping of 192 F3 families, along with the parental lines, was undertaken in 2005 at the three locations. Quantitative Trait Loci (QTL) mapping using QTL Cartographer revealed location-specific QTLs for BLSB resistance, with most of the favorable QTL alleles contributed by the resistant parent CA00106. Analysis using QTL Network V2.0 led to the identification of three QTLs (on chr. 6, 8 and 9) with significant epistatic interactions.

Genetic Resources Program|Global Maize Program

Text in English

INT1617|INT3057