Euphytica (2001) 122, 327-334

Sanjay Katiyar, Satish Verulkar, Girish Chandel, Yang Zhang, Bingchao Huang and John Bennett (2001)
Genetic analysis and pyramiding of two gall midge resistance genes (Gm-2 and Gm-6t) in rice (Oryza sativa L.)
Euphytica 122 (2), 327-334
Abstract: Asian rice gall midge (Orseolia oryzae) is a major pest across much of south and southeast Asia. This pest is genetically diverse and many gall midge biotypes are known to exist in each country. During the last three decades, host plant resistance has proved to be the most effective mechanism of controlling the Asian rice gall midge. Seven genes conditioning resistance to gall midge larvae have been identified in rice (Oryza sativa) and are being used in cultivar improvement programs.However, some of these genes are rendered ineffective by new gall midge biotypes. Increased understanding of genetics, inheritance, allelic relationships and linkage is necessary to maximise the durability of major gene resistance by the pyramiding of these genes.The two genes, Gm-2 and Gm-6(t), are known to confer resistance against a number of biotypes in India and China, respectively. An F₃ population derived from a cross between Duokang #1(donor of Gm-6(t)) and Phalguna (donor of Gm-2) was screened against Chinese gall midge biotype 4 at Guangdong, China, andIndian gall midge biotype 1 at Raipur, India. At each location, separately, a single gene governed resistance. The parallel segregation of 417 F₃ progenies for both biotypes at two locations revealed that recombination had occurred between the two genes, establishing that the two genes are not allelic. However, the two genes Gm-2 and Gm-6(t), were found to be linked with a distance of < 16.3 cM. A number of lines homozygous at one locus and segregating for the other locus were identified and selected. These lines were selfed to obtain lines homozygous for the favourable alleles at both loci (two locus pyramids). This is the first report on use of conventional host-pest interaction method for pyramiding two closely located Gm-resistance loci of dissimilar effects.The implications of deployment of these pyramids within and across country borders, with reference to the prevailing gall midge populations are discussed.
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Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Orseolia oryzae	Rice (Oryza)