Heterosis and combining ability studies in cucumber (Cucumis sativus L.)
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Date
2001
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SKUAST Kahmir
Abstract
Twelve genetically diverse lines (used as females) viz., pioneer Pickling, sweet Delight, Boston Picking, CHC-1, SKAU-K-2, Green Express, CH-20, Sel-75-2-10, SKAU-J-3, Henzil, Market-76 and EC-173924 and four testers (used as males) viz; khira-90, EC-381606, Japanese Long Green (JLG) and Poinsettee were used to generate 48 F1hybrids as per procedure proposed by Kempthorne (1957). The parents (Lines and testers) along with F1hybrids and F2 generations were evaluated over two years ie., kharif 1998 and 1999 at the Vegetable Experimental Farm, Division of Olericulture, SKUAST (K), Shalimar. Observations were recorded for 12 different traits viz., days taken to first female flower appearance, nodal position of the first female flower, days taken to first marketable fruit maturity, number of primary branches plant-1, number of nodes plant-1, number of female flowers plant-1, number of fruits plant-1, fruit length (cm), fruit width (cm), average fruit weight (g), fruit yield plant-1 (kg) and vine length (cm).
The data was analysed to generate information on genetic variability, general and specific combining ability effects, gene action, average degree of dominance, F1 heterosis, F2 residual heterosis and inbreeding depression.
Highly significant differences were found among the lines, testers and hybrid for all the traits both in the individual environments and for data pooled over the environments, confirming that the parents chosen for the crossing were divergent. Genotype x environment interaction for lines, testers and hybrids was, by and large, significant for most of the traits revealing that the parents and hybrids failed to behave similarly in the two environments.
Variance component due to lines was significant except for fruit width. Variance component due to gca (average) and sca effects was significant for all the traits except gca variance for nodal position of the first female flower and fruit length.
On pooled analysis basis, variance due to additive genetic variance was higher in magnitude than the variance due to dominance deviations for all the traits except number of nodes plant-1, number of female flower plant-1, number of fruits plant-1, fruit width, average fruit weight and total fruit yield plant-1. Average degree of dominance was partial for days taken to first female flower, nodal position of first female flower, days taken to first marketable fruit maturity, fruit length and vine length, while as it was in the over-dominance range for rest of the traits.
Parental lines showing high GCA effect for number of traits were SKAU-2 (11 traits), Sweet Delight (8 traits), Japanese Long Green (6 traits), Boston Pickling SKAU-3 (5 traits) and Poineer Pickling and EC-173924 (4 traits). Similarly, sweet Delight and khira-90 revealed high per se performance for 7 traits followed by SKAU-K-2, Boston Pickling and Poineer Pickling possessed very good gca effect and per se performance.
The cross Sel-75-2-10 x Poinsettee possessed high sca effect for 9 traits followed by Green Express x Japanese Long Green (8 traits), pioneer Pickling x Japanese Long Green SKAU-K-2 x EC-381606, EXC-173924 x Poinesette (6 traits) and Sel-75-2-10 and EC-381606, CHC-1 x Poinsette, Boston Pickling x Khira-90 for (5 traits). Similarly, the crosses showing high per se performance for most of the traits were sweet Delight x Japanese Long Green (5 traits) followed by Green Express x Japanese Long Green, SKAU-Kx EC-381606, Poineer Pickling x Khira-90 (4 traits). High sca effect was expressed by the crosses average x average, high x average or high x low performing parents (general Combiners).
F1 heterosis, F2 residual heterosis and inbreeding depression revealed that the gene recombination from differential parental lines could produce high yielding and better performing homozygous lines provided an appropriate breeding methodology is adopted during selection of elite recombinants. Among F1 hybrids, the crosses namely SKAU-K-2 x EC-173924 x Poinsettee, Green Express x EC-381606, Green Express x Japanese Long Green were found heterotic and also had superior mean performance. These elite hybrids thus could be exploited commercially under temperate conditions, as large-scale hybrid seed production in this crop is easy and economical.
Description
PhD Thesis submitted to SKUAST Kashmir
Keywords
Vegetable Science, Combining ability, Cucumber, Heterosis