Development Of Blast And Bacterial Blight Resistant Photo-thermo-sensitive Genic Male Sterile Rice By Marker Assisted Selection

Two-line hybrid rice system as a rice heterosis utilization method was pioneered and widely used in China. Because of reduction of the breeding steps, diversification of the cytoplasm, the broadened choice of male parents, and the efficient in developing higher yield and quality hybrids as compared with three-line system with the cytoplasmic male sterility(CMS), it has become main hybrid rice cultivars in China. The development of photo-thermo-sensitive genic male sterile(PTGMS) lines is the basis for two-line system hybrid rice technology. But as a result of the breeders focused on sterility, rice quality and combining ability, most of popularized two-line hybrid rice varieties in China were susceptible to rice blast and bacterial blight. To introgressing resistance genes into elite PTGMS lines using molecular marker assisted selection with conventional breeding method has been considered as the efficient and cost-effective method to prevent these diseases in two-line hybrid rice production.One rice blast resistance gene Pi2 and three bacterial blight resistance genes Xa7, Xa21 and Xa23, were introgressed into three elite PTGMS lines C815 S, Guangzhan63-4S and Hua328 S by backcrossing, multicrossing, molecular marker-assisted selection(MAS) and pyramiding to develop many rice blast and BB resistant introgression and pyramiding PTGMS lines. The performance of fertility, disease resistance, main agronomic traits, flowering traits, rice quality and hybrid rice agronomic traits were evaluated, and the main results are showed as follows:1. 14 PTGMS lines harboring different resistance genes were selected. Of them, five PTGMS lines harboring Pi2 were named Hua1032 S, Hua1033 S, Hua1034 S, Hua1037 S and Hua1035S; Eight bacterial blight resistant PTGMS lines were selected, including one PTGMS line harboring Xa7 was named Hua1017S; four PTGMS lines harboring Xa7 and Xa21 were named Hua1002 S, Hua1005 S, Hua1010 S and Hua1012S; two PTGMS lines harboring Xa23 were named Hua1006 S and Hua1009S; one PTGMS line harboring Xa7 and Xa23 was named Hua1001 S. one PTGMS line harboring Xa23 and Pi2 resistant to both rice blast and bacterial blight was named Hua1015 S.2. The field evaluation of blast resistance of the new developed lines and their derived hybrids at two blast epidemic sites, Yuanan and Enshi in past two years, showed that the PTGMS lines harboring Pi2, Hua1037 S, Hua1032 S, Hua1033 S, Hua1034 S and Hua1035 S showed from moderate resistant to high resistant against the blast, and Hua1015 S harboring Pi2 and Xa23 showed moderate susceptible to moderate resistant against the blast, but the recipient parents, C815 S and Guangzhan63-4S were highly susceptible to the blast. The hybrids derived from new breeding lines and the susceptible male parent IR24, showed resistant against the blast, and the control hybrids derived from C815 S and Guangzhan63-4S were susceptible to the blast. The pathogenicity assays inoculated with 62 blast prevalent isolates in glasshouse showed that the blast resistant frequencies of six PTGMS lines were 87.1%-98.4% that is equivalent to blast resistant donor parent VE6219 and higher than C815 S and Guangzhan63-4S.3. Seven strains of Xanthomonas oryzae pv. Oryzae, PXO61, PXO99, ZHE173, GD1358, Fu J, YN24 and He N11 were inoculated to eight PTGMS lines and their hybrid combinations for identifying the bacterial blight resistances. The results showed that Hua1006 S, Hua1009 S, Hua1002 S, Hua1005 S, Hua1001 S, Hua1010 S, Hua1012 S and Hua1015 S were from moderate resistant to high resistant against all of seven strains, but the recipient parent C815 S was moderate susceptible or susceptible to the seven strains, and the other recipient parent Guangzhan63-4S was moderate susceptible or susceptible to six strains except that it was resistant to He N11. Most hybrids derived from new breeding lines and the susceptible male parent IR24 showed from moderate resistant to high resistant against the seven strains, and the control hybrids derived from C815 S and Guangzhan63-4S were susceptible to the seven strains. Hua1017 S only harboring Xa7 was susceptible to PXO99, moderate susceptible to Fu J and Yu N24, high resistant against ZHE173, resistant against PXO61 and GD1358, and moderate resistant against He N11, and the hybrids derived from Hua1017 S showed similar resistant level compared with Hua1017 S.4. The characterization results of fertility-sterility alteration in growth chamber showed that the critical temperature points(CTP) of fertility-sterility alteration of Hua1006 S, Hua1009 S, Hua1002 S, Hua1037 S, Hua1034 S, Hua1012 S, Hua1035 S, Hua1015 S and Hua1017 S were at 22℃ of daily mean temperature, and Hua1005 S and Hua1010 S were between 22°C and 23°C, and Hua1032 S and Hua1033 S were between 23°C and 24°C, and Hua1001 was higher than 24°C.5. The results of dynamic observation of pollen fertility-sterility alteration in the field showed that the pollen sterile periods of Hua1006 S, Hua1009 S, Hua1002 S, Hua1037 S, Hua1034 S, Hua1012 S, Hua1035 S, Hua1015 S, Hua1017 S, Hua1005 S, Hua1032 S and Hua1033 S were 71-88 d, similar with C815 S and Guangzhan63-4S. But the pollen sterile periods of Hua1010 S and Hua1001 S were only 61 d and 52 d, respectively, obviously shorter than C815 S and Guangzhan63-4S.6. The results of heading days evaluation showed that the days to heading of all the 14 PTGMS lines were 83-92 d, similar with the three recipient parents, C815 S, Guangzhan63-4S and Hua328 S. The results of the evaluation of agronomic showed that the main agronomic traits of new developed PTGMS lines were similar with the control C815 S, Guangzhan63-4S and Hua328 S, expect that the plant height of Hua1034 S, Hua1015 S and Hua1017 S were higher than the control. The natural spikelet fertilities of Hua1002 S and Hua1034 S were only 28.0% and 38.0%, respectively, lower than the recipient parent C815 S, but the natural spikelet fertilities of the other 12 new PTGMS lines were 47.1%-86.0%, higher than each controls. Hua1015 S and Hua1037 S gave higher hybrid seed yields on account of increased outcrossing rates due to better floral traits under high temperature conditions.7. The results of rice quality traits showed that Hua1034 S reached the third grade standard of national good quality rice. The head rice rate and amylose content of Hua1035 S was 48.8% and 14.1%, respectively, but other rice quality traits of Hua1035 S could reach the second grade standard of national good quality rice. The rice quality traits of the other 12 new developed PTGMS lines were similar with each recipient parents, C815 S, Guangzhan63-4S and Hua328 S.