Female sex-associated RAPD marker in pointed gourd (Trichosanthes diocia Roxb.)

摘要

Pointed gourd (Trichosanthes dioica Roxb.), a perennial vegetable crop is cultivated widely in West Bengal, Bihar and Eastern Uttar Pradesh. It is one of the most nutritive cucurbit vegetables highly used in India due to its availability for about eight months in a year. Pointed gourd is morphologically distinct from the other cucurbitaceous species due to its well-established dioecism (Figure 1) and vegetative means of propagation. In the plant kingdom dioecy is found only approximately in 4 percent of the angiosperm. Dioecism has arisen independently in different families and genera, and several distinct genetic mechanisms regulating dioecy have been found in different plant species. In contrast to the situation found in most animals, where highly differentiated sex chromosomes typically control dioecy, chromosomal heteromorphism isthe exception, rather than rule in dioecious plant species. The presence of sex chromosome has been claimed for some dioecious angiosperms, but only in few cases have these claims been documented3-5. More often the sex ratio in dioeceous plant species is controlled by the expression of allele at one to several locit. In T. dioica, the male and female plants strictly maintain their respective sexual phenotypes. This indicates clear genetic basis of difference between male and female individuals of this species. Pointed-gourd breeding programme has recently been initiated to develop new cultivars. Dioecy represents an inconvenience in pointed-gourd breeding. Currently there is no method for distinguishing between male and female plantlets prior to flowering in T. dioica. A method to determine the gender of plants before flowering would facilitate breeding and selection, by enabling screening for gender at an early stage, thereby simplifying the breeding of male and female plants for different objectives, and saving time and economic resources. Hence the present investigation was carried out to understand the molecular basis of differentiation between male and female genotypes based on RAPD markers.