| Photoperiod and thermo-sensitive genie male sterile (PTGMs) rice plays an important role in hybrid rice breeding. In this study, we sistimaticly evaluated the agronomy traits, critical sterility temperature point, out-crossing characteristic, the broad-spectrum resistance to rice blast fungus of a two-line male sterile line LongS breeded by Rice Institute of Hunan Agricultural University, and also molecularly mapped one major blast resistance gene Pi-LS(t). The main results are presented as follows.1. The LongS posesses an ideal plant architecture with a length of 35-43 cm and a 6.9°of opening angle for flag leaf.2. LongS is a typical photoperiod and thermo-sensitive genie male sterile line. Temperature is the leading factor for its sterility transistion. The critical sterility temperature point is between 22.5 to 22.8℃, and the physiology sterility temperature is around 17.2℃, the suitable growing temperature for seed increasing is between 19.0 to 21.5℃.3. LongS shows an out-crossing superiority. Its peak flowering period is 2 to 6 days after heading. The flowering rate before noon is about 59.09%. The peak daily-flowering period is at 09:00 to 14:00. The opening angle of flower is about 30.64°, and the flowering time lasts 2.5 hours. Its stigma has a strong vitality insisted for 5 days. The stigma exposed rate is high. The clasping spikelet rate is about 3.3%. LongS is sensitive to GA3 which used for releasing the clasping spikelet, the optimal concentration is 15-20 g/667 m2, and the optimal spraying time is on the point of crevasse.4. The rice blast resistance evaluation showed that LongS is highly resistant to all 41 rice blast isolates collected from China and four foreign countries and is a elite rice blast resistace germplasm.5. The investigation of hybrids resistance using LongS as female line, and another PTGM line C815S as a control, the results indicated that the F1 hybrids originated from the cross between LongS and 8 male parents show a higher rice blast resistance compared to the combinations of C815S.6. The genetic analysis using two F2 population derived from the resistant parent of LongS and the susceptible parent of CO39, NPB showed that the segregation ratio of F2 population derived from cross between LongS with CO39 by inoculation with isolate IC-17 is 15 to 1, suggesting that LongS resistance to race IC-17 are controlled by two resistance genes. The segregation ratios of F2 populations crossed between LongS and CO39 or NPB by inoculation with 318-2 and RB7 respectively is 3 to 1, indicating LongS resistance to race 318-2 or RB7 is controlled by single dominant resistance gene.7. A total of 848 SSR and SNP markers were used to evaluate the genomic polymorphism between LongS and CO39 or NPB for futher rice blast R gene mapping. the results showed that 142 polymorphic markers were identified between LongS and CO39 with a percentage of 16.75% of the tested markers; and 287 were identified from LongS and NPB with a percentage of 33.84% of the tested markers.8. To molecularly map the R gene from LongS, a F2 population crossed by LongS and NPB was used for phenotyping inoculated with a isolate 318-2. and the susceptible plants DNA were genotyped with 287 polymorphic markers through BSA and RCA methods. The linkgae analysis indicated that the R gene was linked to two makers M1 and M2 on chromosome 9 within an interval of 1.3 cM. The gene was temperally designated Pi-LS(t). The resistance spectrum comparasion with two previously mapped R genes Pi5 and Pii on this locus showed that LongS express much more broader resistance spectrum than Pi5 and Pii, suggested that Pi-LS(t) may be a new blast R allelic gene.9. A F6RILs population derived from cross of LongS and CO39 was used for genotyping using 114 SSR and SNP markers, a total of 1522.1 cM genetic linkage map was constructed with 23 linkage groups. To futher identify the blast resistance QTLs, the field blast resistance phenotype was evaluated. Combining the phenotype and genotype data,8 minor QTLs were detected using the composite interval mapping (CIM) method, of which located on chromosome 5 between the marker RM8039 and RM18516; chromosome 6 in the interval of marker RM190 and RM19410 and chromosome 10 between the marker RM5304 and RM304.Take together with above results, our data indicated that LongS is an elite two-line male sterile with a good plant architechture, low critical sterility temperature, out-crossing superiority and broad spectrum blast resistance with a major dominant blast R gene Pi-LS(t). The identified linkage molecular markers of Pi-LS(t) are useful for futher gene cloning and marker-assisted rice blast resistance breeding. |
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