Mapping of southern corn rust-resistant genes in the W2D inbred line of maize (Zea mays L.)

Southern corn rust, caused by Puccinia polysora Underw., has destructive potential on the susceptible host. In this study, the resistance inheritance was investigated in an F2 and its F2:3 populations derived from a cross from two inbred lines W2D (resistant) and W222 (susceptible). The 3:1 ratio of resistant to susceptible plants indicated that the resistance is controlled by one dominant gene (named as RppD). The gene RppD was located by means of the F2 population. Total of 11 markers, including five SSR markers, five sequence-tagged site markers and one cleaved-amplified polymorphic sequence (CAPS) marker, were identified to narrow the gene RppD down to a smaller interval. The closest markers flanking RppD were SSR marker umc1291 and CAPS marker CAPS858, with genetic distances of 2.9 and 0.8 cM, respectively. Moreover, RppD might be a novel Rpp resistance gene or haplotype differing from RppQ and RppP25 according to an allelism test among the three crosses W2D × Qi319, W2D × P25 and Qi319 × P25. As a result, RppD haplotype might be helpful to maize germplasm enhancement and disease-resistant breeding.