Marker-assisted breeding of rice lines special for rice noodle-making by pyramiding the Wxg2 and ALKGC genes

Rice noodles are a popular food widely consumed in South Asia. Up to now the breeding progress in the development of rice varieties used for rice noodle-making by conventional breeding methods is very limited, owing to the complex nature of grain quality traits. Fortunately, two functional genes, i.e., Wxg2 (showing high amylose and hard gel consistency) and ALKGC (associated with intermediate high gelatinization temperature), have been identified to have desired starch quality phenotypes for rice noodle-making. This research was carried out to transfer the two major dominant genes from two rice donors HJX74 (carrying Wxg2) and ZX14 (carrying ALKGC) into new rice lines through marker-assisted breeding. Based on the functional mutations of Wxg2 and ALKGC, two sets of allele-specific PCR markers were developed. An intercross was made between HJX74 and ZX14 to develop a F2 population in which marker-assisted selection was applied to select individuals possessing both Wxg2 and ALKGC in homozygous condition. According to the marker genotypes, five homozygous lines were finally selected from 60 F2 progenies. The two-gene pyramided lines were selfed to generate F3 generation. Several promising F3 lines with fine agro-morphological traits were identified and then advanced to F4 generation for further evaluation of grain quality traits. All F4 selected lines exhibited desired starch properties required for rice noodles, demonstrating that marker-assisted pyramiding of Wxg2 and ALKGC is an essential approach to develop the rice lines suitable for rice noodle-making.