CHARACTERIZATION OF GALL MIDGE RESISTANT RICE GENOTYPES USING RESISTANCE GENE SPECIFIC MARKERS

Abstract

Asian rice gall midge (Orseolia oryzae) is one of the major pests of rice which is causing significant economic loss to the crop. So far 11 gall midge resistance genes have been characterized from different rice varieties and seven biotypes of the pest have been identified based on their reaction to these genes. Cultivation of varieties containing single resistance gene has resulted in frequent breakdown of resistance due to emergence of virulent biotypes of the insect. Pyramiding of two or more effective genes in a single cultivar may lead to durable gall midge resistance. In present study about 100 gall midge resistant rice genotypes were screened under field condition against gall midge biotype GMB4M at Warangal and GMB1 in greenhouse at DRR. Furthermore, these entries were genotyped by using five gene specific markers which can detect the presence of Gm1, gm3, Gm4, Gm8 or Gm11 genes with high degree of success. Based on both phenotypic and genotypic analysis, these genotypes were grouped into five phenotypic sets. In Set 1, 17 genotypes showed nil damage at both the locations and amplified one or multiple gene specific alleles. In Set 2, 31 genotypes showed low level of damage (< 20%) at DRR and or Warangal, of which two breeding lines and a land race are likely carry new gene(s). In set 3, 18 genotypes displayed resistance against GMB1 but were susceptible against GMB4M. Set 4 had 6 genotypes that were found resistant against GMB4M but recorded up to 50% plant damage in greenhouse against GMB1. Set 5 had 22 genotypes that were susceptible against both the biotypes and not carried R genes.