Four genes of rice, Oryza sativa L., conditioning resistance to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (X. o. pv. oryzae), were tagged by restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers. No recombinants were observed between xa-5 and RFLP marker loci RZ390, RG556 or RG207 on chromosome 5. Xa-3 and Xa-4 were linked to RFLP locus XNpb181 at the top of chromosome 11, at distances of 2.3 cM and 1.7 cM, respectively. The nearest marker to Xa-10, also located on chromosome 11, was the RAPD locus O072000 at a distance of 5.3 cM. From this study, the conventional map [19, 28] and two RFLP linkage maps of chromosome 11 [14, 26] were partially integrated. Using the RFLP and RAPD markers linked to the resistance genes, we selected rice lines homozygous for pairs of resistance genes, Xa-4 +xa-5 and Xa-4 +Xa-10. Lines carrying Xa-4 +xa-5 and Xa-4 +Xa-10 were evaluated for reaction to eight strains of the bacterial blight pathogen, representing eight pathotypes and three genetic lineages. As expected, the lines carrying pairs of genes were resistant to more of the isolates than their single-gene parental lines. Lines carrying Xa-4 +xa-5 were more resistant to isolates of race 4 than were either of the parental lines ('quantitative complementation'). No such effects were seen for Xa-4 +Xa-10. Thus, combinations of resistance genes provide broader spectra of resistance through both ordinary gene action expected and quantitative complementation.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Agronomy and Crop Science
- Plant Science