Introgression of lac6/tl1/du13 improves the palatability of japonica rice

Abstract

Amylose content (AC) is a crucial determinant of the eating and cooking quality (ECQ) of rice, with low AC varieties exhibiting a softer texture and greater stickiness −attributes that enhance palatability and are desirable in specific culinary contexts. To harness these traits, significant efforts have been made to manipulate AC to improve rice ECQ. Our research utilized the MutMap+ approach to identify LAC6/TL1, a gene that is an allele of Du13, responsible for low AC. LAC6 encodes a C2H2 zinc finger protein, which specifically increases the splicing efficiency of the Wxb allele without affecting the Wxa allele. Functional studies of LAC6 revealed that its proper integration could rectify the undesirable AC phenotype, whereas mutations within this gene led to reduced AC and were associated with shorter grain length and decreased thousand-grain weight. Despite these drawbacks, such mutations positively impact rice palatability, presenting a trade-off between grain size and eating quality. To address the challenges posed by the reduced grain weight associated with LAC6 mutations, we developed a specific molecular marker for LAC6, which has been effectively used in breeding programs to select lac6/tl1/du13 homozygous individuals with larger grain size. Our findings demonstrate that the “small grain” trait associated with lac6/tl1/du13 can be effectively mitigated through combined phenotype-based and marker-assisted selection. This study highlights the potential of lac6/tl1/du13 as a valuable gene for breeding novel, high-quality soft rice varieties through targeted breeding strategies.