Marker-assisted breeding of rice lines special for rice noodle-making by pyramiding the Wx g2 and ALK GC 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., Wx g2 (showing high amylose and hard gel consistency) and ALK GC (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 Wx g2 ) and ZX14 (carrying ALK GC ) into new rice lines through marker-assisted breeding. Based on the functional mutations of Wx g2 and ALK GC , two sets of allele-specific PCR markers were developed. An intercross was made between HJX74 and ZX14 to develop a F 2 population in which marker-assisted selection was applied to select individuals possessing both Wx g2 and ALK GC in homozygous condition. According to the marker genotypes, five homozygous lines were finally selected from 60 F 2 progenies. The two-gene pyramided lines were selfed to generate F 3 generation. Several promising F 3 lines with fine agro-morphological traits were identified and then advanced to F 4 generation for further evaluation of grain quality traits. All F 4 selected lines exhibited desired starch properties required for rice noodles, demonstrating that marker-assisted pyramiding of Wx g2 and ALK GC is an essential approach to develop the rice lines suitable for rice noodle-making.