Conversion of normal inbred lines into quality protein maize through marker assisted selection

Abstract

Protein malnutrition is one of the challenges to ensure nutritional security of the global poor masses especially in rural population of the developing world. Cereals are deficient in some of essential amino acids like lysine and tryptophan. The deficiency leads to one of the protein deficiency disorder like kwashiorkor. Therefore the challenge is to deliver nutritious, safe and affordable food to reduce the impact of nutritional deficiency. Quality protein maize (QPM), contain double the amount of lysine and tryptophan as compared to normal maize is one of the intervention could play vital role to reduce amino acid deficiency. In this context, several efforts have been made to enhance the lysine and tryptophan levels through marker assisted introgression of o2 gene into elite inbred lies of maize. In the present study, opaque2 gene along with phenotypic selection for kernel modification was incorporated using marker assisted backcross breeding (MABB) program into normal inbred line i.e. LM19. This is the parental line of popular single cross hybrids PMH6 in India. HKI 163 was the donor for opaque2 allele. opaque2 gene􀀐based simple sequence repeat (SSR) markers were successfully used for introgression of opaque2 allele. BC2F2 population derived from marker identified BC2F1 individuals were subjected to foreground selection. 86 BC2F2 plants derived from LM19 × HKI 163 cross were screened for o2 gene linked molecular marker. The result showed that 50 plants were heterozygous, 18 plants were homozygous while 15 plants were negative for o2 allele. The o2 carrying homozygous plants were subjected to background selection using sequence tagged microsatellites (STMS) to accelerate the recovery of recurrent parent genome (RPG). The background selection has revealed that the RPG varied from 79􀀐 87 % in BC2F2 generation derived from LM19 × HKI 163 cross. The newly developed near isogenic lines (NILs) from the hard endosperm kernels were evaluated for desirable agronomic and biochemical traits in replicated trials and the best lines were chosen to represent the QPM version of LM19. The agronomic performance of the selected BC2F2 population for LM19 × HKI 163 inbreds showed comparable performance with LM17 in days of anthesis, days of silking and yield and yield component traits.