Mapping of resistance genes to races 1, 3 and 5 of Podosphaera xanthii in melon PI 414723

Abstract

The fungus Podosphaera xanthii affects melon crops and presents several races controlled by race-specific resistance genes.The accession PI 414723 is resistant to races 1, 3 and 5 and it is a suitable source of resistance genes. The inheritance of resistanceto these races was analyzed on 87 F2 plants from the cross of PI 414723 × Védrantais, and resistance to all three races could be explainedby the segregation of a single dominant gene, although a digenic model could also be accepted. A genetic map was assembledwith 206 markers, and co-segregation analysis of resistance phenotypes indicated the existence of two linked loci in linkage group II,one conferring resistance to races 1 and 5 (denominated Pm-x1,5), and the second to race 3 (denominated Pm-x3), located 5.1 cMapart. This study reports for the first time the existence of Pm-x3 and the genetic locations of these resistance genes from PI 414723.

Keywords

• Disease resistance
• molecular marker
• genetic mapping
• powdery mildew.