Improvement Of Amylose Content Of Mid-Indica Rice Xieyou 57 With Molecular Marker-assisted Selection

Xieyou 57, i.e. Xieqingzao A×057, was one of three-line hybrid rice authorized by nation, thanks to its high yield, wide adaptability and high resistance to disease. But it had poor eating and cooking quality, which restricted the most-widely planting. So, it is significant to improve its eating and cooking quality. The main reason of its poor eating and cooking quality was that the amylose content (AC) of 057, the male parent of Xieyou 57, was too high. So, it is the key to lower the AC of 057 for the improvement of the quality of Xieyou 57. The AC is controlled by waxy gene (Wx) and it had been reported that molecular markers connected with Wx gene had been used for improvement of rice quality in rice breeding, but less succeeded in fact. Using four varieties with low AC as the donor parent of Wx gene, we have succeeded in lowering the AC of 057 and selected some improved lines and elite hybridized combinations through backcrossing with 057 and using the PCR-AccⅠmarker –assisted selection. The main results are as follows: 1. Improvement of the quality of 057 To lower the AC of 057, backcrosses were made respectively using four indica varieties (R367,91499, Yanhui 559, Hui 527) as the donor of elite Wx gene and 057 as recurrent receptor parent, and the elite Wx gene was introgressed from donor parent to 057 through backcross with PCR-AccⅠmarker-assisted selection. After successive backcrosses, the AC of 057 was reduced, and the elite agronomic traits of 057 were also retained. 2. Selection of the elite hybridized combinations The hybridized combinations were made between Xieqingzao A and the stable backcross generations. The comparison of the AC among the hybrid combinations showed as follows: 1)among 29 hybridized combinations which male parents genotype was TT, 8 hybridized combinations, i.e. 27.6%, could reach the grade Ⅰof the China National Standard for high quality paddy in AC and 86.2% of those could reach grade Ⅲ and over; 2) among 23 hybridized combinations with GG genotype male parents , only 2 could reach the grade Ⅲ in AC and was the 8.6% of those, but none with gradeⅡcould be found in this test; 3) among 10 hybridized combinations with TT genotype male parents, 6 could reach the gradeⅢ and none with gradeⅡcould be found either in this test. The result indicated that the quality of hybrid combinations could be improved through selecting TT genotype lines as the parents by PCR-AccⅠmarker. Four elite hybridized combinations had been selected through the block test. The AC of three elite hybridized combinations all reached gradeⅠand one reached gradeⅡof the China National Standard for High Quality Paddy and the yield had been enhanced in a different degree, comparing to Xieyou 57. the two hybridized combinations, i.e. 04ZH1185 and 04ZH1218, which female parents were Xieqingzao A and male parents were 04ZH086 and 04ZH181 respectively, had almost identical agronomic performance with Xieyou 57 including the grain type, and the other two, i.e. 04ZH1291 and 04ZH1306, which female parents were Xieqingzao A and male parents were 04ZH446 and 04ZH495 respectively, had similar agronomic performance to Xieyou 57, which grain type was longer than Xieyou 57 and reached the standard of high quality paddy, which appearance quality of rice had been improved a lot comparing to Xieyou 57. The four elite hybridized combinations and the four improved lines were cooked with Xieyou 57 and 057 as control. Their rice was observed and degusted primarily, and the result showed that the rice of the four male parents appeared soft, sticky, glossy, and still soft after it was cooled. While the rice 057 appeared hard after it was cooled as well as dry and fluffy. For Xieyou 57, the rice was dry and fluffy too, which turned hard after cooled. So it had bad mouthfeel. Comparing with them, the four selected hybrid combinations appeared soft but not sticky, which had gloss and good mouthfeel, but they showed a little hard after cooled. 3. The relationship between the genotype of Wx and the AC, gel consistency (GC)...