Resistance response of yellow maize inbreds and F1 crosses against Philippine downy mildew [Peronosclerospora philippinensis (Weston) C.G. Shaw]

Abstract

Maize is one of the world's most important staple crops, yet various pests and diseases impede its optimal production. Philippine maize downy mildew disease (PDM) caused by Peronosclerospora philippinensis (Weston) Shaw is one of the most devastating diseases in corn-growing areas in Asia. Breeding for resistant varieties is the most cost-effective and environmentally safe alternative for controlling the disease. In this study, we evaluated the resistance responses of yellow maize inbreds and hybrids against PDM to select promising genotypes for genetic analysis and varietal improvement. Resistance trials under greenhouse conditions were conducted to investigate the PDM resistance response of 14 selected CIMMYT lines (CMLs) and IPB Var 6 (susceptible check) to select potential parents prior to hybridization. CML 431 and CML 452 were identified to have significantly low disease incidence among the test genotypes. Subsequently, disease evaluation of the two inbred lines with putative DM resistance, four experimental hybrids derived from these inbred lines, and checks was performed in the field. Across three validation trials, inbred CML 431, and hybrid CML 452 × CML 431 showed degrees of resistance to PDM. This study's findings enabled the identification of resistant lines to downy mildew for the generation of mapping populations for genetic association studies, as well as the establishment of experimental units for transcriptomics research.