Application Of Molecular Markers In Rice Resistant Breeding And Identification Of Hybrid Rice Seeds Purify And Authenticity

Rice (Oryza sativa L.) is one of the most important cereal crops in the world. The bacterial blight (BB) is a significant disease of rice. And the brown planthopper (BPH) is a significant insect pest of rice. The application of resistant cultivars has generally been considered to be the most effective and economical means for BB and BPH control.In order to breed resistant cultivars to BB and BPH, a highly BB resistant line CBB23 and a highly BPH resistant line B5 are used as donors, and elite restores yangdao6 and 1826 are used as recipients. The crossing and multiple-crossing were used to pyramid BB resistant gene Xa23 and BPH resistant gene Bph14/Bph15. EST marker C189 was used to select Xa23, and SSR markers MRG2329 and MS5 were used to select Bph14 and Bph15 respectively in the segregating population. Some gene-pyramided lines were achieved, in which Xa23 and Bph14 or/and Bph15 were combined through molecular marker-assisted selection in seedling and selection of agronomic traits in adult stage. The resistance level to BB and BPH of 18 important lines was evaluated. The results indicated that the BB and BPH resistance of 18 lines were improved obviously. All lines showed resistance to BB. Except 2 Bph14-single introgression lines showed moderate susceptible, the others showed moderate resistance to high resistance to BPH insects. The survey revealed that marker-assisted selection is an efficient way for Xa23 and Bph14/Bph15 selection and pyramiding in rice breeding programs.Application of hybrid rice has made a great contribution to rice yield increasing on a large scale. But in recent years, there existed some problems in hybrid seed quality, such as biological admixture, mechanical admixture and impurity of hybrid seeds resulted from confusion of similar hybrids or wrong use among seed-shape-like genotypes. The traditional field identifying method in Hainan province was used to identify hybrid seeds purity and authenticity before the normal sowing season. But this method has some disadvantages such as time-consuming and high expensive. With the development of molecular biology and biotechnology, DNA molecular markers were studied and applied in hybrid seeds purity and authenticity identification. The molecular markers of application are usual RAPD and SSR. But SSR technique shows more reproducibility and stability than that of RAPD technique.In order to discuss the dependability and accuracy of hybrid seeds purity and authenticity identification using SSR technique, in this study, 100 SSR primer pairs were screened in a two-line hybrid rice combination Liangyou932 and its parents, of which five SSR primer pairs showed polymorphism. A special primer pairs RM302 were screened from these five primer pairs in 6 different types of biological admixture of Liangyou932. The 200 single seeds of Liangyou932 were tested using RM302. The seed purity was 90.50%, which was approximate to the field purity (90.60% in Hainan and 91.57% in Wuhan, respectively). 100 SSR primer pairs were screened in a two-line hybrid rice combination Ejingza No.1 and its parents, as a result, five SSR primer pairs showed polymorphism. RM206 and RM340 among these five primer pairs were selected to identify true or false of sample A and B sequestered by Seed Managing Station of one county. The results indicated that the DNA bands amplified by the two primer pairs are different between the two samples and Ejingza No. 1. We can determine that the two samples are not the seeds of Ejingza No.1. The results of this research suggested that SSR technique could be used in seeds purity and authenticity of hybrid rice. The results of identification are precise and credible.