Document Type : Research Paper
Rice Research Institute of Iran, P. O. Box 1658-41635, Rasht, Iran.
International Rice Research Institute, Manila, The Philippines.
Blast, Pyricularia grisea (Cooke) Sacc., is one of the most destructive diseases of rice worldwide and can
result in significant reductions in yield. The use of resistant cultivars is the most economical and effective
way of controlling rice blast. A variety of DNA markers, including plant defense-related candidate
gene markers are available for genetic characterization and molecular analysis of rice. A set of 161
recombinant inbred lines, RILs, from a cross between Nemat, an improved and high yielding cultivar, and
Anbarboo, a traditional and aromatic rice, was used to identify defense-related candidate gene, RFLP
and SSR markers linked to components of resistance to blast, i.e. infection type, lesion density, the percent
of diseased leaf area, and lesion size in rice. The RILs were tested using two single blast isolates in
greenhouse, and field population of blast in blast nursery in International Rice Research Institute,
Philippines, in 2000–2001. Of the 86 defense-related candidate gene, 153 RFLP, and SSR markers 26
defense-related candidate gene, 66 RFLP, and 85 SSR markers were polymorphic in two parental lines.
Results showed that a defense gene, b8, a NBS-LRR originated from barley, closely linked to different components of resistance to blast. The defense genes of r5, r7, PrP2, and ERS from rice, maize, and
Arabidopsis, respectively, have had minor effects on different components of resistance to blast. The
RFLP markers, i.e. RZ536, RG351, RZ76, RZ397 on chromosomes 7, 11 and 12, and the SSR markers
including RM224, RM179, and RM277 on chromosomes 11 and 12 were tightly linked to componentsof resistance to blast. The linked markers can now be used for resistance gene pyramiding and markerassisted
selection in the breeding population. The results suggested the presence of race-specific resistance
genes exhibiting strong differential pathogenhost interaction. We need to incorporate new sources of gene pool to make the genetic base broaden.