STUDIES ON IDENTIFICATION OF MOLECULAR MARKERS FOR BUCKEYE ROT (Phytophthora nicotianae Breda de Hann. var. parasitica(Dastur) Waterhouse) RESISTANCE IN TOMATO (Solanum lycopersicum L.)

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2016
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ABSTRACT Present study was carried out for identification of molecular markers for buckeye rot resistance in tomato. In this study first of all genetic diversity was assessed among 32 tomato genotypes. For this EST-SSR primers were in silico synthesized by downloading 4200 EST sequences of tomato from NCBI website followed by finding out of contigs and singletons using EGassember server with further extraction of SSR containing sequences using SSRITsoftware with final designing of 55 EST-SSR primers with Primer3 software of which 20 EST-SSRs were custom synthesized. These EST-SSRs along with ISSRs and genomic SSRs 25each were used to conduct genetic diversity studied among 32 tomato genotypes revealing polymorphism of 96.77%, 95.36% and 97.36%, respectively. On data analysis with NTSYS-pc version 2.0 similarity matrix with range of 0.252 to 0.615 was observed with maximum similarity of 61.5% between ‘EC-521’ and ‘EC-8591’ and minimum similarity of 25.2% between ‘EC-528373’ and ‘EC-528367’. Dendrogram divided all genotypes in two main clusters ‘A’ and ‘B’ with 25 and seven genotypes, respectively. Genetics of inheritance was found out by screening 100 F2 segregants, derived from a cross between susceptible parent ‘Solan Lalima’ and resistant parent ‘EC-251649’, with fungal inoculum which showed that 95 were susceptible and five were resistant giving a ratio of 3.8:0.2. The calculated value of χ2 was found more than the tabulated value showing that observed F2 ratio did not fit into the expected Mendelian ratio for monogenic inheritance of buckeye rot in tomato revealing polygenic control of this disease. 153 primers were used for parental polymorphism survey which consisted of 44 ISSR, 89 genomic SSR and 20 EST-SSR primers. Out of these 93 primers were found polymorphic which included 36 ISSRs, 41 genomic SSRs and 16 EST-SSRs which were used for genotyping studies of F2population. The phenotypic and genotypic data of F2 population was used for construction of linkage map using MAPMAKER/EXP version 3.0b which resulted in construction of 12 linkage groups. LG2 was the largest group spanning a distance of 4584.9 cM followed by LG6 which covered a distance of 39.3 cM. All primers covered total genetic map distance of 4660.7 cM. QTL were constructed using software QTL Cartographer which detected total 22 QTL with placement of 20 QTL on chromosome 2 and single QTL each on chromosome 6 and 7. This is the first study for identification of QTL for buckeye rot resistance in tomato which can further be used for marker assisted selection and other molecular studies.
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<h1>You have exceeded your usage quota. Please contact gshukla [at] iitk.ac.in </h1>, tomatoes, genotypes.
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