Recent advancement for breeding and maintenance of Parthenocarpic cucumber (Cucumis sativus L.)

Cucumber (Cucumis sativus L.) is one of the important and popular cucurbitaceous vegetable crops grown throughout the tropical and subtropical regions of the world. It belongs to the family Cucurbitaceae having a somatic chromosome number 2n = 2x = 14 with a genome size of 243.5 Mb (Huang et al., 2009). The usefulness of any genetic mechanism in a crop plant is always evaluated by its utilization in improving productivity. Among the different mechanisms, exploitation of the heterosis in vegetable crops, sex mechanism, more particularly gynoecy which has been universally adopted in cucurbits. Gynoecy, a condition where all the flowering nodes produce only pistillate flowers, can be exploited for improving yield and economizing hybrid production. India is being considered the home of cucumber possesses a vast range of genetic diversity and variability for both growth and fruit characters, but this diversity has not been fully utilized for its genetic improvement.  The development of gynoecious varieties with parthenocarpic traits has become major challenge to the cucumber breeders to use it as a parent in F₁ hybrid development for achieving higher yield, earliness, uniformity and suitability for protected cultivation. Therefore, there is an urgent need to develop gynoecious hybrids with parthenocarpic traits. Gynoecy coupled with parthenocarpic cucumber is a yield and quality-related parameter and a high value vegetable crop immensely suited for off season cultivation under protected condition because parthenocarpic varieties do not require pollination for fruit setting. In commercial production parthenocarpic cultivars are beneficial especially when pollination is difficult or heavily impacted by environmental conditions. Parthenocarpic varieties do not produce large number of seeds, even when pollinated. This attributes to high cost of seed production and makes the seeds of these variety more expensive than other varieties. In these case using of growth hormones we can manipulate the sex of the plant and maintain gynoecious parthenocarpic plant easily via spraying of GA3, silver nitrate, silver thiosulphate and other which may suppress ethylene production induces male flowers to do selfing to keep the genotype true to type.