INHERITANCE OF GYNOECY, PARTHENOCARPY AND YIELD RELATED TRAITS IN INDIAN CUCUMBER

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Date
2016
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DIVISION OF VEGETABLE SCIENCE ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE, NEW DELHI –
Abstract
The present investigation was undertaken during 2012-2014 with the objectives (i) to study the heterosis, combining ability and gene action for earliness and yield traits (ii) to study the inheritance of gynoecy and parthenocarpy (iii) generation mean analysis for earliness and yield traits (iv) molecular mapping of gynoecious (F) locus in cucumber. The seven diverse inbred lines of cucumber were crossed in a half diallel fashion without reciprocals to generate 21 F1 hybrids. These seven parental lines and their 21 F1 hybrids were evaluated for estimation of heterosis, combining ability and gene action. The observation were recorded for ten quantitative characters viz. node number of first female flower, days to first female flower anthesis, days to fruit set from opening of first female flower, days to first fruit harvest, number of fruits per plant, fruit length, fruit diameter, average fruit weight, vine length and yield per plant. Based on the performance of 21 F1 hybrids three best performing hybrids PPC-2 × Pusa Uday, GPC-1 × Punjab Naveen and PPC-2 × Punjab Naveen showed 64.51%, 55.61%, and 54.57% heterosis respectively, over standard check Pusa Uday for yield per plant. Hence, these hybrid can be exploited commercially for earliness and yield per plant and may be tested under multi-locational trials. The most outstanding parental lines involved in all F1 crosses which showed best GCA effects are GPC-1, PPC-2 and Pusa Uday. The F1 hybrid showed promising results when atleast one of the parental lines exhibiting high GCA effect for yield and its component traits were involved in the crosses. Highest SCA effect for total yield per plant was shown by hybrid GPC-1 × PPC-2, PPC-2 × Pusa Uday and GPC-1 × Punjab Naveen. These combinations may be exploited for commercial hybrid production. From the above cross combination it is clear that gynoecious as one of parent in cucumber hybrid development holds immense potentiality for exploitation of hybrid vigour with respect to earliness, yield and other yield related traits. The analysis on genetic components of variance revealed over dominance gene action and narrow sense heritability was found to be < 50 per cent for most of the characters except for average fruit weight, where, partial dominace is more predominant. The over dominance and low narrow sense heritability for most of the 102 characters studied suggested the significance of heterosis breeding to get higher gain in cucumber. The results of generation mean analysis showed the significance of additive, dominance and epistatic interaction in most of the crosses for ten important quantitative characters. Simple mass selection would be effective for improvement of the characters governed by additive gene effects, heterosis breeding for characters governed by dominance gene effects and breeding plan based on restricted selection by way of intermating the most desirable segregants followed by selection and/or diallel selective mating system would be most appropriate for characters where duplicate epistasis was predominant. Complementary epistasis was observed for yield per plant, which would increase the heterosis in positive direction. The segregation of F2 population into 3 (gynoecious): 1 (monoecious) plant suggested that single dominant gene controled the gynoecious sex in cucumber particularly in gynoecious genotype PPC-2 and GPC-1, and this can be transferred to horticulturally desirable varieties through backcross breeding. The χ2 value indicated a good fit for segregation of parthenocarpy (early, late and non-parthenocarpy) in the F2 population and backcrossed populations confirmed with the expected ratio of 1:2:1 and 1:1, respectively. These data support that parthenocarpic trait in cucumber is controlled by incompletely dominant gene. In present experiment a linkage map of seventeen SSR markers along with the F locus covering 100.4 cM distance was developed. The F locus was flanked by five linked SSR markers viz., SSR13251, UW020605, SSR11798, SSR007281 and UW084131 were located at 1.0, 4.5, 5.9, 5.0, and 7.0 cM distances respectively. SSR 13251 was the closest markers flanking the gynoecious (F) locus at a distance of 1.0 cM, which will be a critical useful application in marker assisted breeding for selection of stable gynoecious lines with high efficiency. Hence, identification of tightly linked SSR markers would be of enormous potential in the context of developing Indian gynoecious cucumber lines through marker assisted backcross breeding. 103 सार खीरे में स्त्रील िंगी, अलिषेक फ ि एविं उपज सम्बिंलित क्षणों का अध्यि, िामक शीषषक स
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T-9638
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