Studies on combining ability, molecular diversity and response to late blight (Phytophthora infestans (Mont.) de Bary) in tomato (Solanum lycopersicum L.) under polyhouse condition
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation was carried out at Vegetable Research Center of Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, with the objectives to assess the genetic variability, molecular diversity, heterosis, combining ability, gene action, screening for late blight disease and estimation of percentage fruits damage due to Tuta absoluta in tomato. The analysis of variance for RBD and combining ability revealed significant genetic differences among 36 tomato genotypes for the fifteen yield related and ten quality traits under study. The magnitudes of PCV estimates were higher than the corresponding GCV estimates for all the characters. Moderate to high GCV together with moderate to high heritability and genetic advance as per cent of mean was reported for majority of the characters under study except characters related to earliness viz., days to 50 per cent flowering, day to first fruit set and days to fruit ripening. A total of 20 SSR markers tested out of which 16 were polymorphic and 4 markers had shown monomorphic on agarose gel. Among eight genotypes of tomato total number of 46 bands exhibited by these 16 SSR primers and among them 43 was polymorphic and 3 were monomorphic. The range of amplified products was 100-700bp approximately and number of alleles per locus varied from two to six. Average number of bands per primer was 2.86. A range of polymorphism was observed from 50 per cent to 100 per cent with an average of 93.23 per cent. The PIC value ranged from 0.117 to 0.891 with an average 0.596. Jaccard’s similarity coefficient varied from 0.52 to 0.94 with an average value of 0.70. PBT-9 and PBT-13 (0.94) were found to be the most similar genotypes among the eight genotypes studied followed by PBT-10 and PBT-13 (0.90). Minimum Jaccard’s similarity coefficient was found in PCT-1 with PBT-2 and PBT-5 (0.52). The clustering pattern obtained by SSR primer showed that PCT-1 (cherry tomato line) and PBT-4 (potato leaf type) showed deviation from existing cluster. Hybrids, PCT-1 x PBT-5, PBT-9 x PBT-5, PBT-9 x PBT-2 and PBT-2 x PBT-13 were found promising for earliness while, for fruit yield, PCT-1 x PBT-5, PBT-2 x PBT-13, PBT-9 x PBT-4 and PBT-5 x PBT-4 were found promising hybrids. For most of the fruit quality traits promising hybrids were PCT PCT-1 x PPT-2, PBT-9 x PBT-2, PBT-2 x PBT-4 and PPT-2 x PBT-10, hence these crosses could be utilized as commercial hybrids for earliness, high yielding and industrial processing, respectively. PCT-1 was identified as a best general combiner for maximum number of yield related and fruit quality traits followed by PPT-2 and PBT-5. The best specific combiner were PBT-2 x PBT- 13 followed by PBT-13 x PBT-10, PBT-9 x PBT-5, PCT-1 x PBT-5 and PBT-9 x PBT-4 for most of the yield related and fruit quality traits studied. Among all yield related and fruit quality traits most of the characters were under the control of non additive gene action with over or partial dominance effect except fruit firmness, hence these characters are suitable for hybrid breeding. For late blight disease resistant reaction, out of all F1 hybrids six cross combinations showed resistant and thirteen hybrids showed moderately resistance reaction. Among 28 hybrids, minimum average percentage fruits damage due to Tuta absoluta was found in PCT-1, PCT-1 x PBT-5 and PCT-1 x PBT-13.
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