Genetic Analysis for Earliness and Yield Components using Gynoecious and Monoecious Lines in Cucumber ( Cucumis sativus L . )

Cucumber (Cucumis sativus L., 2n = 2 x =14) is an important summer vegetable of cucurbitaceae family. In India it is cultivated from higher altitude to plains including river beds. In north Indian plains, two crops are grown in a year i.e. spring-summer and kharif, while in hills it is cultivated as an autumn summer crop. Cucumber is well known for its economic importance as food plant, mainly grown for its edible tender fruits used as salad, pickles, dessert fruit, rayata preparation and even brined on commercial scale in almost every part of the world. It is an ideal crop for the peoples suffering from jaundice, constipation and other associated diseases. India is being home of cucumber possesses vast genetic variability for vegetative and fruit characters. The one of the most important factors limiting fruit yield in slicing and processing cucumber are low fruiting ability and yield suppression due to its inherent fruiting habits [1]. Development of high yielding gynoecious lines or hybrids mainly depends on genetically superior parents, together with suitable breeding methodology. Gynoecious varieties are becoming popular among cucumber growers because of its high yield, earliness and best suited to protected cultivation [2-3]. The nature and magnitude of gene action involved in expression of quantitative traits is important for successful development of crop varieties. Also, the correct choice of parents for hybridization is crucial for development of cultivars. Depending on the genetic architecture of the traits, recombinant breeding is the most appropriate approach to combine various desirable traits. Therefore, it is essential to have knowledge of gene effects concerned with inheritance of many traits to formulate any breeding methods. The success of selection mostly depends upon the amount of genetic variability present in the parental lines used. Selection generally carried out from locally existing germplasm results in low magnitude of improvement due to less variability. Therefore, a broad genetic base should be utilized for faster and higher magnitude of success. Use of diverse genotypes in hybridization programme creates such broad genetic base [4]. In spite of wide genetic variability available in this crop little attention has been given for improvement of this crop. Hayman (1954) [5] and Griffings (1956) [6] offered an excellent mean of obtaining Abstract Twenty one F1 hybrids were developed from crossing of 7 diverse genotypes including two gynoecious lines of cucumber in a half diallel mating system. These twenty one F1 hybrids along with their seven parents were evaluated to study the gene action in gynoecious and monoecious lines for various earliness and yield components in cucumber. Analysis of variance revealed the presence of highly significant differences among the genotypes representing that these were diverse for the traits studied. The prevalence of over dominance effect for 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 and total yield per plant, whereas nearly dominance effect was observed for number of fruits per plant and partial dominance effect was observed for fruit length, fruit diameter and average fruit weight. For average fruit weight, narrow sense heritability was greater than 50% which is an indication of predominance of additive gene action, while for remaining traits narrow sense of heritability was less than 50%, which suggests the preponderance of non-additive gene action. Therefore, in the present study, the predominance of non-additive gene action and low narrow sense heritability was recorded for most of the important earliness and yield contributing characters suggested the significance of heterosis breeding to obtain higher gain in cucumber improvement.