Allelic Diversification of the Wx and ALK Loci in Indica Restorer Lines and Their Utilisation in Hybrid Rice Breeding in China over the Last 50 Years

Abstract

Hybrid rice technology has been used for more than 50 years, and eating and cooking quality (ECQ) has been a major focus throughout this period. Waxy (Wx) and alkaline denaturation (ALK) genes have received attention owing to their pivotal roles in determining rice characteristics. However, despite significant effort, the ECQ of restorer lines (RLs) has changed very little. By contrast, obvious changes have been seen in inbred rice varieties (IRVs), and the ECQ of IRVs is influenced by Wx, which reduces the proportion of Wxa and increases the proportion of Wxb, leading to a decrease in amylose content (AC) and an increase in ECQ. Meanwhile, ALK is not selected in the same way. We investigated Wx alleles and AC values of sterile lines of female parents with the main mating combinations in widely used areas. The results show that almost all sterile lines were Wxa-type with a high AC, which may explain the low ECQ of hybrid rice. Analysis of hybrid rice varieties and RLs in the last 5 years revealed serious homogenisation among hybrid rice varieties.

Control of Grain Shape and Size in Rice by Two Functional Alleles of OsPUB3 in Varied Genetic Background

“…This implied that OsPUB3 regulated GW by a rare molecular mechanism. OsPUB3 encodes a U-box type E3 ubiquitin ligase, which has been verified to have ubiquitination activities [ 53 ]. There are very few examples of overexpression and knockout/knockdown of the same gene exhibiting a similar phenotype [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ].…”

Molecular and genetic bases of rice cooking and eating quality: An updated review

“…In current rice breeding programs, the major Wx alleles in modern cultivated rice are Wx a , Wx b , and Wx in (Zhang et al, 2019). Over 50 years of experience in developing hybrid rice in China, it was found that almost all sterile lines have the Wx a allele, explaining why the hybrid rice varieties have a low CEQ (Pan et al, 2022). Introduction of other alleles into new varieties may facilitate breeding of rice varieties with low AAC, soft texture of cooked rice, and transparent grain appearance.…”