Identification Of SCAR Markers Linked To The Bentazon Susceptible Lethality Gene And Marker-assisted Selection In Rice

The rice (Oryza sative L.) cultivar 8077S is a photo-thermo-sensitive genic male sterile (PTGMS) line carrying the bentazon susceptible lethality gene. The selfed-seed seedlings of 8077S killed by bentazon —a selective .herbicide, while is safe for its F₁ hybrids and all other normal varieties. The single recessive gene is transferred into PTGMS lines of two-line hybrid rice, the self-fertile hybrid can be deleted from cross-fertile hybrid rice during seed germination and seedlings stage treated with spraying bentazon (above 300mg/L), which effectively prevents seed production from self contamination by the sterility instability. So breeding a series of male sterile lines with bel gene is very important. However, the expression frequency of this recessive gene is rather low in conventional breeding. And it needs many backcross and inbred generations by turns for breeding a new variety with the bel gene, which will expend lots of labor, material and need longer time. By the molecular marker assisted selection for the breeding, the linkage drag can be greatly reduced in less generations and the efficiency of breeding be enhanced.So the main purpose of this study is trying to find out closely linked molecular markers of bel,as well as to establish aneffective working procedure by Marker-assisted selection.The results obtained are as follows:1. Five methods for extracting and purifying DNA from rice leaves were compared. The PCR products all showed clear bands.2. First,the optimal reaction system was structured by studying the factors affecting the rice RAPD reaction.Then,two pieces of polymorphic fragment amplificated by random primer S20,S316 were screened. One was S20-420 and another was S316-600.3.Two pairs of SCAR primers were designed based on the sequence of cloned fragments.The SCAR primers included original RAPD primers. Only a 423bp bandwas present in susceptible plants, and no any band in resistant plants with primerSC01. Only a 606bp band was present in susceptible plants,a 630bp band in resistantplants (Homozygous),and the two bands in resistant plants (Heterozygous) withprimer SC02. SCAR markers were more reliable than RAPD markers.4.8077S was used as a female parent to cross with three varieties, Minghui 63 > Feng35 n R318-5. Backcrossed progenies that contained bel gene were selected using theprimer SC02. The results suggested it made a great reduction in time and labourconsumer to transfer bel gene into elite rice lines with application of market-assistedselection.5.By using single dry seeds of rice as experimenting materials,DNA extraction werestudie, and Primer SC01 was used on the testing of seed purity of hybrid rice.