Development of hybrid rice germplasm

Nine three-line hybrids were elevated to the national cooperative tests (NCT): PR30262H, PR30263, PR31181H, PR31204H, PR31205H, PR31215H, PR31276H, and PR35015H. PR31204H (7755 kg/ha) achieved a 14.7% heterosis for yield over PSB Rc 28 in the DSNCT at PhilRice CES. Yield heterosis of the PYT hybrid PR31728H (7908 kg/ha) reached 28.5% during the DS [dry season] relative to PSB Rc28. In WS [wet season], yield heterosis of better hybrids in the yield trial nurseries ranged from 2.0% to 25.0%. The best comparable check to the hybrids evaluated in the WS yielded 5081 kg/ha to 6200 kg/ha. DS results indicate that the number of filled grains (FG) per panicle in the F1 correlated positively and very significantly with spikelet number (SN) per panicle and panicle length (PL) of the hybrid. Correlation was negative and highly significant with spikelet fertility (SF) ratings. PL in the F1 was also significantly and linearly associated with both heights (HT) of the F1 and the male parent (MP). WS results extended associations noted from the DS for FG of the F1 with the SN, FG, PL, and SF of the MP. However, PL of the hybrid showed significant correlation with the PL of the MP, but not with HT of either the F1 of MP. The 31 new TGMS lines had more stable sterility/fertility characteristics than previous selections. Evaluation and seed multiplication of TGMS lines, including those developed at IRRI, continued at the male-fertile environments (MFE) in Carranglan, Nueva Ecija and Tublay, Benguet [Philippines]. Data indicate that Benguet might be more suitable for TGMS lines with lower critical sterility points, i.e. 24-25 deg C. Based on the mitDNA differences between a WA-type CMS and normal, fertile rice, specific PCR primers were designed and two sets of primers were shown to amplify highly discriminative profiles between the maintainer and the CMS or hybrid. The optimized PCR assay detected the presence of the off-type maintainer in CMS population and hybrid seedlings using bulked DNA assay. This technology is for verification tests. A special study determined whether a calibration model for seed purity (in terms of inert matter) can be designed based on the values obtained in comparison with the trained analysts of NSQCS. Preliminary results showed that near-infrared (NIR) technology (Infratec 1241 Whole Grain Analyzer, Foss Tecator, Sweden) could be used for rapid inert matter analysis of A-line and inbred seeds. Nucleus seeds produced for A and B lines of Mestizo 1, 2 and 3 amounted to 311 and 445 kg, respectively. Moreover, 5147 kg of A-line breeder seeds, 5567 kg B-line, and 4074 kg R line were produced, exceeding targets. Breeder seeds produced will be sufficient for 87% of one the 288 ha targeted for foundation seed production