Abstract:

The rice (Oryza sativa) cultivar 8077s is a photo-thermo-sensitive gene male sterile (PTGMS) line carrying the bentazon susceptible lethality gene. The gel bel made the self-seeding of 8077s killed by bantazon, while is safe for its F₁ hybrids and all other normal varieties. 8077s prevents effectively seed production from self-contamination by the sterility instability. It is purpose that the bel gene be identified and marked by RAPD and SCAR methods in order to apply in the molecular marker assisted selection for the breeding (MAS). The study was carried out using bulked segregant analysis (BSA) in an F2 population from a cross between rice cultivars 8077s harboring bentazon susceptibility trait and Feng 35 harboring bentazon resistance trait. The analysis indicated that segregated proportion was 1∶3 between susceptible and resistant individual in F₂ population. This ratio was accord with Mendel’s Law of Segregation. The character of bentazon susceptibility controlled by a single recessive gene (bel). A total of 210 arbitrary 10-mer oligonucleotide primes were screened on the genomic DNA of 8077s and Feng 35 by RAPD technique. Among primes produced polymorphic RAPD bands between 8077s and Feng 35. Nine plants of the bentazon susceptible lethality and resistance lethality plants were selected for DNA extraction to establish susceptible and resistance gene pools respectively. Above primers were repeatedly screened from the BSA. Two primers (S20 and S316) were obtained from the primers. The result shows that polymorphic RAPD fragments were S20-440 (440 bp) and S316-590 (590 bp). The genetic distance between the bel gene and two RAPD markers was 7.97 and 12.132 cM respectively. The fragments of RAPD markers were recovered, cloned and sequenced. According to the sequence, two pair of specific SCAR primers were designed and synthesized. The specific bands with size of 423 bp and 606 bp respectively on the single herbicide susceptible plant of F2 were amplified with primers SC01 and SC02. The genetic distance closely to bel gene was 10.66 and 7.04 cM. And SCAR markers were applied in assisted selection for a bentazon susceptible lethality gene (bel) in rice. The studies laid foundations for the breeding with MAS and researching further bel gene.

Key words: Rice, Herbicide Susceptible Lethality Gene (bel), RAPD markers, Bulked Segregant Analysis