Marker assisted selection for β-carotene rich maize: two-level selection procedure in BC2 generation

Abstract

This paper is a part of the breeding program conducted at the Maize Research Institute "Zemun Polje", with the aim to convert the standard maize to β-carotene rich genotypes adapted to temperate regions using the marker assisted selection. When SSR marker specific to the crtRB1 gene has been tested on parental lines, distinct polymorphism was observed between the donor and recurrent parents. The same marker has also been validated in BC1 generation when heterozygous individuals were clearly distinguishable from the homozygous dominants. The results presented herein refer to two-level selection procedure in BC2 generation. First, BC2 plants were analyzed with crtRB1-specific molecular marker to separate heterozygotes from dominant homozygotes. Percentage of heterozygous plants was approximately 50%, which was in accordance with the expected Mendelian ratio of 1:1. Second, the selected heterozygotes were screened with 30 polymorphic SSR markers distributed throughout the maize genome to identify genotypes with the highest recovery of recurrent parent’s genome (RPG). The RPG values among three analyzed parental lines and their respective progenies ranged from 85-99%. For each line separately, RPG values were: 86-97% (RP1), 90-95% (RP2) and 85-99% (RP3). Plants with RPG above 95% were selfed to produce BC2F2 generation in which homozygous recessive individuals would be identified. Those genotypes will be subjected to biochemical and phenotypic evaluation to confirm their nutritional and agronomical superiority. Finally, these β-carotene enriched lines, as well as the resulting improved hybrids, can be used in the biofortification programs.