INTROGRESSION OF OPAQUE-2 GENE INTO THE GENETIC BACKGROUND OF POPCORN USING MARKER ASSISTED SELECTION

Abstract

Biofortification of a natural snack like popcorn is important for improved nutrition and health of children and adults. This study was aimed at introgressing opaque-2 gene, a high lysine/tryptophan gene into the genetic background of popcorn. Field experiments were carried out at the Teaching and Research Farm (TRF) of the Federal University of Technology, Akure (FUTA) during the 2016 dry and wet season while biochemical and molecular analyses were carried out in the Biochemistry Laboratory, FUTA and Bioscience Laboratory, International Institute of Tropical Agriculture (IITA) respectively. Nine parental genotypes were used which comprised three popcorn maize varieties and six Quality Protein Maize (QPM) varieties. F1s were developed by crossing the parent genotypes using North Carolina mating design I. The F1s developed were evaluated for gene action and heritability. The ten F1 were also advanced to F2 by self pollination. Segregated kernels from each genotype were screened on the light box. Kernel modification 2 (25% opaque) and 3 (50% opaque) were selected. Selected kernels were analyzed biochemically for protein and tryptophan contents. The allelic state of opaque-2 gene in the selected F2s was determined using SSR marker phi 112. Additive gene effect and narrow-sense heritability were found to be most important for traits such as days to 50% flowering, days to 100% flowering, ear height and 100 grain weight. Protein and tryptophan contents and quality index for unpopped and popped F2 of crosses of QPM and popcorn were significantly higher than popcorn checks. Protein and tryptophan contents and quality index of F2s of crosses of QPM and popcorn reduced significantly when subjected to heat treatment. Unpopped protein content, unpopped tryptophan content and popped tryptophan content were highly correlated with one another. Phi 112 SSR marker showed dominant pattern of polymorphism, amplifying DNA fragments between 154bp and 160bp for the ten F2.