IDENTIFICATION OF DNA MARKERS LINKED TO A BLAST RESISTANCE GENE IN RICE

摘要

Identification of DNA markers closely linked to a blast (Pyricularia oryzae Cav.) resistance gene and establishment of an indirect selection method for the blast resistance gene based on linked DNA markers are reported. A pair of near isogenic lines, K80R and K79S, were developed using a local Chinese indica rice cultivar, Hong-jiao-zhan, as the resistant donor and IR24 as the recurrent parent. Ten putatively positive markers were identified by screening 177 mapped DNA markers. Using 143 plants composed of the F_2 population of K80R/K79S, three restriction fragment length polymorphism (RFLP) markers (RG81, RG869 and RZ397) on chromosome 12 of rice were verified to be closely linked to the blast resistance gene. The resistance genotypes of each F_2 resistant individual were determined by inoculation of the F_3 lines. RG869 was found to be most closely linked to the resistance gene, with a genetic distance of 5.1 cM. To fine map this gene with more DNA markers, the bulk segregation analysis procedure was employed to identify the random amplified polymorphic DNA (RAPD) markers linked to the resistance gene. Six of 199 arbitrary primers were able to produce positive RAPD bands. Tight linkage between the resistance gene and the three RAPD bands, each from a different primer, was confirmed after amplification of the DNA of all the F_2 individuals. The linked DNA fragments were cloned and sequenced. The results of specific amplification were in agreement with those of RAPD analysis. The half-seed RAPD analysis procedure for blast resistance detection was established. The amplified DNA patterns of the extract from the endosperm half of the mature seeds were identical to those of the total DNA from the leaves.