Genetic Analysis and Identification of RAPD Markers Linked to Northern Corn Leaf Blight Disease Resistance in a White Maize Population

Northern corn leaf blight (NCLB) is an important disease occurring in maize producing areas. Understanding the genetic nature of NCLB is regarded as a primer step in maize breeding programs. This study used the resistant line Sids-63 (Sd-63) and the susceptible line Sids-7 (Sd-7) to develop F1 and F2 generations. P1, P2,F1 and F2 were used to study the genetic nature and to detect RAPD markers associated with the NCLB resistance gene(s) using bulked segregant on analysis (BSA). The genetic studies revealed that the inbred line, Sd-63, recorded low disease severity (ranged from less than 5% to 10 %) and the inbred line, Sd-7, recorded high disease severity (ranged from 26 % to more than 75 %). F1 severity ranged from less than 5% to 50%. The F2 severity ranged from less than 5% to more than 75 %. The observed ratio (number of plants with high: low disease severity) fitted the Mendelian ratio, 3:1, and suggested the operation of one gene pair in this cross. The degrees of dominance for F1 (h1) and F2 (h2) gave significant negative values (–0.86 and –0.71 respectively). The heritability value for the tested cross was 92.00% and the estimated number of genes was 1.1, indicating that there was a difference in resistance genes between the two inbred lines. Thirty-eight primers were screened to identify two RAPD markers; namely, Pr11180 and Pr11300 linked to NCLB susceptible genotypes. Results from the two RAPD markers fitted the expected Mendalian ratio, 3:1, according to ?2-test .The regression analysis showed that the relationships between the two markers, Pr11180 and Pr11300, and the phenotype of the F2 individuals were significant and they recorded a determination coefficient (r2) = 0.54 and 0.60,for the two markers, respectively