Induction and molecular characterization of guava variants generated through mutation breeding
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Date
2016
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Punjab Agricultural University, Ludhiana
Abstract
The present study entitled “Induction and molecular characterization of guava variants generated through mutation breeding” was carried out during year 2015-2016. The research work was conducted at the Fruit Research Farm, Department of Fruit Science and Molecular Biology Laboratory, School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana. Induction of variation is the key to improve existing potential cultivars, lacking few important traits. The guava cultivars Shweta and Lalit are promising, however, lack the traits of commerce, particularly the development of uniform coloured pigmentation on outer skin and hard seeds, respectively. To induce variation, mutation induction approach was adopted. Buds of Shweta were exposed to gamma rays at different doses viz., 10, 20, 30, 40, 50, 60 and 70 Gy followed by patch budding of putative mutated buds on L-49 rootstock. Seeds of guava cultivars Lalit and Shweta were exposed to gamma rays at the doses of 0, 25, 50, 75, 100, 125 and 150 Gy. Generated variants were evaluated for vegetative characters based on UPOV descriptors. Statistically significant difference for all the traits were observed among generated variants. 21 SSR markers were used for molecular characterization of variants. Out of 21 primers used on 384 mutants, maximum number of mutations were identified for mPgCIR19 primer mapped to linkage group Lg:10 at 85 cM and minimum number of mutants were identified by markers mPgCIR40 and mPgCIR93. A mutant plant L207 generated by irradiating Lalit at 50 Gy resulted variation at maximum (8) different positions within the genome. The dendrogram generated using SSR markers grouped mutants into nine clusters and maximum similarity of 100 per cent was showed by B115 and B116. Whereas B201 and B310 showed minimum similarity of 64 per cent. Out of total 384 plants generated, 143 plants were selected on the basis of pigmentation of leaves. 40 SSR primers used for the molecular characterization of pigmented leaf variants generated were identified in M1V0. Out of 40 primers, maximum number of mutants were generated or identified by mPgCIR236 primer and minimum number of mutants were identified by mPgCIR418 and mPgCIR209. Plant S102 of cv. Shweta irradiated at 25 Gy, showed variation at maximum (19) different positions. The dendrogram generated using SSR markers grouped mutants into seven clusters. The maximum similarity of 99 per cent was observed in putative mutants B114 and B116, whereas B203 and B107 showed minimum similarity to the tune of 71 per cent. To conclude, the generated mutants have showed diverse variation at morphological (vegetative characters) and molecular level, which is expected to be translated into desired fruit characters for the anticipated traits.