MSc

Asian rice gall midge Orseolia oryzae Wood-Mason (Cecidomyiidae: Diptera) is regarded as a serious pest of rice with a number of biotypes. Genes Gm1, Gm2, Gm4 and Gm8 are few major genes identified to confer resistance against different biotypes of rice gall midge. The current study, entitled “Identifying donors for gall midge resistance from traditional rice varieties by functional markers,” was undertaken in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani and Rice Research Station, Moncompu during the year 2015-16 with the objectives of identifying traditional rice varieties of Kerala with gall midge resistance genes Gm1, Gm2, Gm4 and Gm8 using associated functional markers and field level validation of the identified gene sources under pest stress condition.
The Simple Sequence Repeats (SSR) markers RM444 linked to gene Gm1, LRR del linked to gene Gm4, PRP flanking Gm8 and Sequence Characterised Amplified Region (SCAR) marker PF10 linked to gene Gm2 were used to check the presence of these genes in the 26 traditional rice varieties under study. Varieties like W1263 for Gm1 gene, Phalguna for Gm2, Abhaya for Gm4 and Aganni for Gm8 were used as checks for the presence of these genes and TN 1 was used as susceptible check for all the genes.
Among the 26 traditional rice varieties screened, 11 confirmed the presence of the gene Gm1 by producing an allele at 320 bp with the primer RM444. Seven varieties confirmed Gm2 gene in its genome by producing an allele at 600bp, 10 varieties produced an allele at 350bp with LRR del primer confirming the presence of Gm4 and 12 varieties confirmed the presence of Gm8 gene with an allele at 300bp with PRP primer.
Five varieties viz, Paluveliyan, Thavalakkanan, Thekken Cheera, Veluthittaryan and Velutha Vattan showed the presence of two genes in combination, another five varieties, Arrikkirai, Vellari, Kalluruli, Chettivirippu and Kaathikannan
confirmed the presence of three genes in combination and one variety, Parambuvattan showed the combination of all the four genes.
Screening of 22 rice varieties with resistance genes under pest stress condition at Rice Research Station, Moncompu, during kharif 2015 revealed that the varieties with gene Gm1 showed resistance reaction towards the gall midge biotype 5 of Kuttanadu region. Varieties with Gm2, showed moderate resistance while, varieties with Gm8 and Gm4 showed moderately susceptible and susceptible reaction respectively. This shows that the biotype of gall midge in Kuttanadu has virulent action for the genes Gm4 and Gm8.
Arrikkirai having Gm1, Gm2 and Gm8 showed resistance reaction (0.52%) to gall midge in field screening. Parambuvattan, which is having all the four genes (Gm1, Gm2, Gm4 and Gm8) also showed resistance to gall midge at field level with a mean percentage gall infestation of 0.92%.
When Gm1 came along with Gm4 and in combination with Gm4 and Gm8, the varieties showed moderate resistance whereas, Gm4 and Gm8 genes in combination produced susceptible reaction in the varieties.
This study conclusively proves that Gm1 is the gene conferring resistance to gall midge biotype 5 prevailing in Kuttandu rice tract of Kerala. Different combinations of genes Gm1 and Gm2 can confer durable resistance. The varieties which have Gm1 and Gm2 genes can be used as donors for pyramiding these genes in the popular rice varieties by marker aided selection, to develop Essentially Derived Varieties (EDVs) to tackle the incidence of gall midge.