Dharminder Kumar

Genetic Variability, Correlation and Path Coefficient Analysis in Tomato

Tomato (Solanum lycopersicum L.) yield in India is below world averages. To increase productivity, it is necessary to develop superior varieties/hybrids. The efficiency of selection depends upon the nature and magnitude of genetic variability and degree of transmissibility of desired characters. Because yield is a complex character, its direct improvement is difficult. Twenty-six genotypes of tomato were assessed to determine the nature and magnitude of variability, correlation, and path coefficient analysis between yield and yield-contributing characters. The analysis of variance (ANOVA) revealed highly significant differences among all genotypes for the characters. The genotype ‘EC-357838’ had the highest mean value for number of fruit per plant, total soluble solids, and yield per plant. High PC phenotypic coefficient of variability (PCV), genotypic coefficient of variability (GCV), and heritability estimates, coupled with high genetic gain, were observed for plant height, number of fruit per plant, yield per plant, and fruit weight, indicating that these characters are under additive gene effects and more reliable for effective selection. Correlation indicated that yield was significantly and positively associated with number of fruit per plant and per cluster. Path analysis at the genotypic level indicated that fruit weight had the most positive direct effect on yield per plant followed by number of fruit per plant, fruit diameter, and number of fruit per cluster. Direct selection on the basis of fruit weight, number of fruit per plant, fruit diameter, and number of fruit per cluster is reliable for yield improvement in tomato.

Parthenocarpic Gynoecious Parental Lines of Cucumber Introduced from Netherlands for Developing High-Yielding, Quality Hybrids

ABSTRACT Development of parthenocarpic gynoecious hybrids in cucumber (Cucumis sativus L.) has enormous importance for its successful cultivation under protected conditions because of low cost of hybrid seed production. Therefore, the present study was carried out to determine the combining ability, nature of gene action, and heterosis for total soluble solids, cucurbitacin content, fruit color, and marketable yield per hectare in cucumber. The experimental material comprised 48 F1 crosses, developed by crossing 16 lines (8 gynoecious) with 3 testers during the year 2011. Parents (16 lines and 3 testers) and the 48 hybrids, along with two standard checks (“KH-1” and “Pusa Sanyog”), were planted in a randomized complete-block design during the year 2012 for their comparative evaluation. Experimental results revealed that lines LC-1–1, CGN-21585, LC-28–8, CGN-20953, and testers Japanese Long Green and K-75 were superior on the basis of mean performance and general combining ability. The cross combinations LC-1–1 × K-75 (monoecious), CGN-21585 × Japanese Long Green (gynoecious), CGN-19533 × K-75 (gynoecious), CGN-20953 × Poinsette (gynoecious), and LC-28–8 × K-75 (monoecious) were found to be the best on the basis of mean performance, specific combining ability, and heterosis. Estimates of σ2SCA were higher in magnitude than those of σ2GCA (average), thereby indicating the predominant role of non-additive gene action governing these traits. Therefore, heterosis breeding could be exploited commercially for the development of high-yielding, quality parthenocarpic gynoecious hybrids in cucumber.

Heterotic potential, potence ratio, combining ability and genetic control of yield and its contributing traits in cucumber (Cucumis sativus L.)

ABSTRACT The present investigation was undertaken in F1 population of 48 crosses, developed by crossing 16 lines (8 gynoecious) and 3 testers during the year 2011. All the parental lines and their F1 hybrids were evaluated in randomised complete block design for yield and its contributing traits during the year 2012. Experimental results revealed that parental lines LC-1-1, CGN-20953, CGN-19533, Gyne-5, LC-15-5 and testers Japanese Long Green and K-75 were found superior on the basis of mean performance and general combining ability effects. The cross combinations LC-1-1 × K-75 (monoecious), CGN-19533 × K-75 (gynoecious), CGN-20953 × Poinsette (gynoecious), Gyne-5 × K-75 (gynoecious) and LC-3-3 × Poinsette (monoecious) excelled based on per se performance, specific combining ability and heterosis studies. Further, performance of top 10 heterotic hybrids illustrated the presence over dominance effects in all the crosses except in one cross, where no dominance was observed. Gene action studies indicated that non-additive gene action governed all the traits under study, suggesting the importance of heterosis breeding for the development of high yielding stable parthenocarpic gynoecious hybrids in cucumber.

Morphological characterization of newly introduced lettuce (Lactuca sativa L.) germplasm through principal component and regression analyses

Twenty seven newly introduced genotypes of lettuce collected from different indigenous and exotic sources were characterized with respect to economically important traits by using principle component and regression analyses. Significant differences were observed among the genotypes for all the characters under study. CGN-10944 performed best among all the genotypes for most of the traits under study. Principal component analysis indicated that the first five factors had variances of 3.88, 2.78, 1.47, 1.42 and 1.24 with 25.87%, 18.57%, 9.81%, 9.49% and 8.26% of total variation, respectively and aggregating to 72.01% of total variation. The highest positive values of different traits in different components indicated that main emphasis should be given on the gross head weight (X 2 ), polar (X 6 ) & equatorial diameter (X 7 ) and seed vigour index-I (X 12 ) & II (X 13 ) to have higher yields in lettuce. To quantify the importance of each variable in predicting yield, multiple linear regression model was developed. The coefficient of determination (R 2 ) in linear regression model revealed that 94% of total variation in yield per plot (X 15 ) was influenced by days to marketable maturity (X 1 ), gross head weight (X 2 ), heading percentage (X 4 ), seed germination (X 11 ), seed vigour index-II (X 13 ) and severity of bacterial soft rot (X 14 ). Therefore, main emphasis should be given on days to marketable maturity, gross head weight, polar & equatorial diameter, heading percentage, seed germination, seed vigour index-I & II and severity of bacterial soft rot during selection and hybridization programmes for yield improvement in lettuce.