Genetic Diversity in Rice (Oryza sativa L.) Genotypes Resistant and Susceptible to the Asian Rice Gall Midge Orseolia oryzae (Wood-Mason)

Genetic diversity among nine gall midge [Orseolia oryzae (Wood-Mason)] resistant and three susceptible rice (Oryza sativa L.) genotypes, comprising of cultivars, breeding lines and landraces, was studied in terms of polymorphism using 358 SSR primers representing the whole genome. Of the 154 polymorphic primers, 82 were found to be highly polymorphic and informative. Number of alleles amplified by these primers ranged from two to seven. Highest polymorphism (40.7%) was noted with primers from chromosome 3. The average of polymorphism information content (PIC) was 0.589. Cluster analysis based on the allelic diversity clearly demarcated the cultivars, landraces and breeding lines into different groups. The genotypes did not distinguish into gall midge resistant and susceptible groups. Two of the landraces, Aganni and Jhitpiti, showed least diversity despite diverse geographical sources of their collection. One of the breeding lines, RP2068-18-3-5, displayed distinctness from all the other genotypes tested. Diversity among the genotypes tested is more evident with respect to directed breeding efforts through human intervention rather than natural evolution of gall midge resistance.