In order to understand rice blast resistance gene patterns in rice landraces from Myanmar and Laos, we analysed the Pita, Pib, Pikh, Pi9 and Pi5 genes in 80 landraces through the use of functional molecular markers and functional fragment sequencing. These landraces were separated into four haplotypes (H1–H4) based upon three mutations identified in the Pita sequence. All four haplotypes were detected among landraces from Myanmar, whereas only the H1 and H2 haplotypes were detected among landraces from Laos. We additionally grouped landraces carrying 0–4 resistance genes into 18 genotypes based upon their resistance-susceptibility patterns and found that 16 of these genotypes were detected among Myanmar landraces at relative frequencies ranging from 2.50–12.50%, while 10 were detected among landraces from Laos at relative frequencies of 2.50–42.50%. The ‘Pib( + ) pikh(−) pi9(−) pi5(−) pita(−)’ genotype was found to be dominant, accounting for 12.5 and 42.5% of landraces from Myanmar and Laos, respectively. The Pib, Pikh, Pi5 and Pita genes were detected in 52.50, 32.50, 37.50 and 30.00% of landraces from Myanmar respectively, whereas they were detected in 52.50, 12.50, 30.00 and 17.50% of landraces from Laos, respectively. The Pi9 gene was rarely detected among analysed landraces and was particularly rare in those from Laos. These findings suggest that rice landraces from Myanmar are more genetically diverse than those from Laos, with clear differences in blast resistance gene patterns between landraces from these two countries.

Analysis of mating type can provide an evaluation of the population genetic diversity of the rice blast fungus, Magnaporthe grisea. According to the sequences of MAT1-1 and MAT1-2 genes of the fungus, two pairs of PCR primers specific to the MAT1-1 and MAT1-2 alleles were designed, and the PCR thermal profile was also optimized. To confirm its application in mating type assessment, 10 tester isolates were tested by PCR. The PCR amplification pattern of these tester isolates corresponded to their known mating type. Furthermore, 150 rice-field isolates from Fujian Province were mated with tester isolates GUY11 and KA3 side by side and also tested by PCR. Results showed that 95.1% of 123 fertile isolates were the same in mating type as determined by both PCR-amplified allele-specific fragments and mating with GUY11/KA3. Among 27 sterile isolates determined by GUY11 and KA3, seven were MAT1-1 and 20 were MAT1-2 as determined by PCR. This study indicates that PCR is applicable in assessing M. grisea mating type and especially is capable of predicting the potential mating type of sterile isolates in the natural population of the fungus.

A rice cDNA library was screened using OSK3 protein kinase as bait in a yeast two-hybrid system. The gene encoding oxalate oxidase was one of the positive clones interacting with OSK3 protein kinase. The interactions were verified by detecting expression of the reporter gene lacZ. The results suggest that oxalate oxidase is a downstream element in the disease resistance signal cascade mediated by OSK3 protein kinase in rice.