A rare Waxy allele coordinately improves rice eating and cooking quality and grain transparency

Abstract

In rice ( Oryza sativa), amylose content (AC) is the major factor that determines eating and cooking quality (ECQ). The diversity in AC is largely attributed to natural allelic variation at the Waxy ( Wx) locus. Here we identified a rare Wx allele, Wx ^mw , which combines a favorable AC, improved ECQ and grain transparency. Based on a phylogenetic analysis of Wx genomic sequences from 370 rice accessions, we speculated that Wx ^mw may have derived from recombination between two important natural Wx alleles, Wx ⁱⁿ and Wx ^b . We validated the effects of Wx ^mw on rice grain quality using both transgenic lines and near‐isogenic lines (NILs). When introgressed into the japonica Nipponbare (NIP) background, Wx ^mw resulted in a moderate AC that was intermediate between that of NILs carrying the Wx ^b allele and NILs with the Wx ^mp allele. Notably, mature grains of NILs fixed for Wx ^mw had an improved transparent endosperm relative to soft rice. Further, we introduced Wx ^mw into a high‐yielding japonica cultivar via molecular marker‐assisted selection: the introgressed lines exhibited clear improvements in ECQ and endosperm transparency. Our results suggest that Wx ^mw is a promising allele to improve grain quality, especially ECQ and grain transparency of high‐yielding japonica cultivars, in rice breeding programs.

Abstract

In the present study, a rare Wx allele, Wx ^mw which may have derived from recombination between two important natural Wx alleles in rice, was identified as a promising allele to improve grain quality, especially cooked rice taste and grain transparency of high‐yielding japonica cultivars, in rice breeding programs.