Molecular marker-assisted selection for improved cooking and eating quality of two elite parents of hybrid rice

Long-te-fu (LTF) and Zhan-shan 97 (ZS) are two key female parents for the generation of indica hybrid rice, which have greatly contributed to the achievement of rice production in China. However, the high amylose content (AC) in the endosperm, controlled by the Waxy (Wx) gene encoded granule-bound starch synthase I, of both lines results in poor cooking and eating quality of the milled rice. Our previous studies have shown that AC was correlated with the ability to excise intron 1 from the leader sequence of the Wx transcript, and which is responsible by a single nucleotide polymorphism (G or T) located at the first nucleotide of the splice donor site of Wx intron 1. Thus, a CAPS marker was subsequently developed, and with this molecular marker-assisted selection (MAS) we successfully introgressed the Wx-TT locus of rice cultivars with good quality intermediate AC into LTF-B and ZS-B. These were subsequently introduced into their relevant male-sterile lines (LTF-A and ZS-A) to generate improved indica hybrids. In the selected lines LTF(tt)-B and ZS(tt)-B, the AC was reduced to a relatively low level (15%). Consequently, the hybrids crossed from the selected lines had dramatically reduced amylose levels. In the field trials, the agronomic performance in the improved lines and their hybrids was examined and compared to the originals. The other key factors involved in rice cooking and eating quality were also improved in the selected lines and their hybrids.