Marker assisted selection for β-carotene rich maize: validation of the gene-specific marker in BC1 generation

Abstract

Worldwide, modern grain breeding programs widely implement marker assisted selection (MAS). Molecular markers are being used in two ways: to control the target gene (foreground selection) and to accelerate the reconstruction of the recurrent parent genotype (background selection). Marker analysis allow breeders to discard plants without allels of interest prior to pollination, reducing the size of breeding population. Marker assisted selection for the qualitative traits, which are regulated by the action of a single or several genes and are clearly phenotypically defined, achieved the best results. The improvement of β-carotene content using crtRB1-specific molecular marker is one of the successful examples of MAS. The introgressed inbreds possessing favourable allele of crtRB1 and improved hybrids with increased β-carotene can be used in the biofortification program. The results presented herein are 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. The utility of SSR marker specific to the crtRB1 gene in foreground selection has been already tested on parental lines and distinct marker polymorphism was observed between the donor and recurrent parents. The objective of this study was to validate the ability of the same SSR marker to detect homozygous dominant and heterozygous plants separately in BC1 generation. Heterozygous individuals were clearly distinguishable, therefore they will be selected and backcrossed with the recurrent parent to produce BC2 generation. Percentage of heterozygous plants identified in BC1 generation was approximately 50%, which is in accordance with the expected Mendelian ratio of 1 O2O2 : 1 O2o2. The use of the crtRB1-specific marker will be extended in the next generation of MAS for β-carotene enriched lines for growing in temperate regions.