Abstract

The genetic diversity for resistance against blast, a major disease on rice, was assessed in the land race collections of Manipur, India, a region reported to be associated with origin of rice. The presence of eight well characterized genes, that is Pi-b, Pi-z, Piz-t, Pi-9, Pi-40, Pi-5, Pi-a and Pi-ta that were known to confer resistance to different isolates of blast were analyzed through polymerase chain reaction (PCR) assay using gene specific molecular markers. The characterization of one hundred and eight accessions revealed the presence of these genes in the range of two to seven confirming the rich diversity for this economically important trait in these native landraces. The genetic diversity for resistance appears to be associated with the high levels of incidence of blast in the hilly uplands of Manipur, a feature that characterizes the rice cultivation of this region. The natural gene pyramids having diverse combinations of resistant genes provide the breeders a great opportunity to transfer and deploy these genes to provide adequate security against this deadly disease of rice in India, a country characterized by highly varied agro-climates and diverse growing conditions.  

Key words: Manipur, genetic diversity, gene, blast disease.