Molecular tagging of a gene for resistance to brown planthopper in rice (Oryza sativa L.)

An introgression line derived from an interspecific cross between Oryza sativa and Oryza officinalis, IR54741-3- 21- 22 was found to be resistant to an Indian biotype of brown planthopper ( BPH). Genetic analysis of 95 F-3 progeny rows of a cross between the resistant line IR54741- 3- 21- 22 and a BPH susceptible line revealed that resistance was controlled by a single dominant gene. A comprehensive RAPD analysis using 275 decamer primers revealed a low level of ( 7.1%) polymorphism between the parents. RAPD polymorphisms were either co- dominant ( 6.9%), dominant for resistant parental fragments ( 9.1%) or dominant for susceptible parental fragments ( 11.6%). Of the 19 co- dominant markers, one primer, OPA16, amplified a resistant parental band in the resistant bulk and a susceptible parental band in the susceptible bulk by bulked segregant analysis. RAPD analysis of individual F-2 plants with the primer OPA16 showed marker- phenotype co- segregation for all, with only one recombinant being identified. The linkage between the RAPD marker OPA16(938) and the BPH resistance gene was 0.52 cM in coupling phase. The 938 bp RAPD amplicon was cloned and used as a probe on 122 Cla I digested doubled haploid ( DH) plants from a IR64xAzucena mapping population for RFLP inheritance analysis and was mapped onto rice chromosome 11. The OPA16(938) RAPD marker could be used in a cost effective way for marker- assisted selection of BPH resistant rice genotypes in rice breeding programs.