An integrated strategy of phenotypic selection for endosperm modifiers and molecular marker-assisted foreground and background selection has been adapted in this study for conversion of six elite maize inbreds in India, namely CM137, CM138, CM139, CM140, CM150 and CM151, into QPM versions. The donor lines used were CML161, DMRQPM-03-124 and DMRQPM-58. All the parental lines were first analyzed using 100 polymorphic microsatellite/SSR markers, which revealed high genetic divergence among the selected lines. Foreground selection was carried out on BC1F1, BC2F1 and BC2F2 progenies using opaque2 specific umc1066 and phi057 SSR markers. Nearly 30 polymorphic SSR markers covering the maize genome were employed in background selection for identification of BC1F1 and BC2F1 individuals with the highest recovery of recurrent parent genomic background. Phenotypic selection for endosperm modifiers was carried out (using the standard light box test) on the backcross progenies in each generation for recovery of segregants with good kernel texture. Biochemical analysis for total endosperm protein content and tryptophan content percentage was undertaken using standard procedures on the BC2F2 progenies for identification of promising o2/o2 genotypes with high nutritional value and proper kernel texture. During the winter season of 2007/08, the opaque2 homozygotes from the BC2F2 populations, identified using MAS, were further selfed to generate BC2F3 families. Further, these BC__2F3 was analyzed for endosperm protein and tryptophan content and selected genotypes were used to generate BC2F4. The study led to the conversion of elite maize lines that are parents of three popular single-cross hybrids (PEHM2, PEEHM5 and Parkash) into QPM versions.

Global Maize Program

English

No CIMMYT affiliation

Lucia Segura

INT3057