Marker-Assisted Backcrossing (MABc) to Improve Eating Quality with Thin Seed Coat and Aleurone Layer of Non-Glutinous Japonica Variety in Rice

Abstract

Brown rice is composed of rice bran, pericarp, seed coat, and aleurone layers, and the rice bran layer contains a large number of substances useful for the human body, such as dietary fiber, α-tocopherol, α-tocotrienol, and vitamins. However, more than 90% of these substances are removed when polished, and white rice has the disadvantage of losing food-related ingredients, such as umami-related amino acids, when compared to the unpolished group. In this study, we tried to develop new breeding lines with a thinner seed coat and aleurone layer to provide high eating quality with softer chewing characteristics and processability in rice grain. We detected an SNP for foreground selection for the backcross population by comparing genome sequences between Samgwang and Seolgaeng and developed high eating quality brown rice breeding lines by applying marker-assisted backcrossing (MABC) breeding programs to backcross populations between Samgwang and Seolgaeng using KASP markers. SNP markers for foreground selection were identified to improve eating and processability through SNP mapping of Samgwang and Seolgaeng with SSIIa as a target gene in this study. Line selection according to genotype of KASP markers was successful in BC1F1 and BC2F1 generations, with the recurrent parent genome recovery ratio ranging from 91.22% to 98.65%. In BC2F1 seeds of the selected lines, thickness of the aleurone layer was found to range from 13.82 to 21.67 μm, which is much thinner than the 30.91 μm of the wild type, suggesting that selection by MABc could be used as an additional breeding material for the development of highly processed rice varieties. These lines will be useful to develop new brown rice varieties with softer chewing characteristics and processability in rice grain.

Marker-assisted introgression of wild chromosome segments conferring resistance to fungal foliar diseases into peanut (Arachis hypogaea L.)

“…Specially for introgression of wild genes, marker-assisted backcrossing (MABC) is essential, as it enables a rapid recovery of the recurrent parent genome, the pyramiding of multiple useful genes into the same genotype, and considerable time saving ( Frisch and Melchinger, 2005 ; Bharadwaj et al., 2022 ; Kim et al., 2022 ). Nevertheless, very few genomic segments of Arachis wild species containing genes of interest have been well-defined to date.…”

Development of SNP Markers from GWAS for Selecting Seed Coat and Aleurone Layers in Brown Rice (Oryza sativa L.)

“…For images of half-cut staining seeds, the total cutting area and staining area were calculated using the ImageJ program, to measure the thickness of the seed coat and aleurone layers [ 28 , 29 ]. The experiment was repeated at least 4 times and the results are expressed as average values [ 30 ].…”

Genetic Research and Plant Breeding

“…These results are useful for developing new markers for MAS (marker-assisted selection), selecting candidate genes in map-based cloning, and producing efficient high-throughput genome-wide genotyping systems for Korean temperate japonica rice varieties. In addition, Kim et al [22] measured the thickness of seed coat and aleurone layers using a set of 294 rice varieties. They also found candidate genes for selecting the thickness of seed coat and aleurone layers by performing GWAS analyses using whole-genome resequencing data.…”

“…The utilization of DNA markers in a markerassisted backcrossing (MABc) program significantly increases selection efficiency. Kim et al [22] attempted to develop new breeding lines with a thinner seed coat and aleurone layer to provide a high eating quality with softer chewing characteristics and processability in rice grain. Line selection according to genotype of KASP markers was successful in the BC 1 F 1 and BC 2 F 1 generations, with the recurrent parent genome recovery ratio ranging from 91.22% to 98.65%.…”