Characterization and Molecular Mapping of Two Novel Genes Resistance to Pythium Stalk Rot in Maize.

Pythium stalk rot caused by Pythium inflatum is becoming a more and more serious disease in maize, which has caused severe yield loss in China in recent years. Deployment of resistant maize varieties is the most effective way to control this disease. Searching for the resistant maize germplasm and identifying the resistance genes is the vital process in breeding program. The maize inbred line X178 previously showed high resistance to Pythium stalk rot. Thus, this study aimed to reveal the gene(s) resistance to Pythium stalk rot in X178 by resistance inheritance analysis using the derived F2 and F2:3 genetic populations. The results showed that two independently inherited dominant genes carried by X178 are responsible for its resistance relative to the susceptible parent Ye107, designated RpiX178-1 and RpiX178-2, which were respectively located on regions of maize chromosome (chr.) 1 bin 1.09 and chr. 4 bin 4.08, and respectively flanked by markers umc2047 and bnlg1671, and bnlg1444 and umc1313 by linkage analysis. Subsequently, RpiX178-1 was finely mapped between markers SSRZ8 and IDP2347, with the genetic distances of 0.6 and 1.1 cM, respectively and the physical distance of the target region was about 700 kb. RpiX178-2 was also further located between markers bnlg1444 and umc2041, with a genetic distance of 2.4 cM. Morover, we confirmed that the two genes RpiX178-1 and RpiX178-2 were newly identified and different from those genes known on chrs. 1 and 4, according to results of allelism testing. Herein, we newly identified two genes resistance to P. inflatum, which provided important genetic information for resistance to Pythium stalk rot in maize.