Breeding for gynoecy in bitter gourd (Momordica charantia L.)
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Date
2019
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Department of Vegetable Science, College of Horticulture, Vellanikkara
Abstract
Bitter gourd (Momordica charantia L.), is one of the most popular vegetable from cucurbitaceae family. Though monecy is the predominant sex form in bittergourd, gynoecy has been reported in bitter gourd from India. The present investigation entitled ‘Breeding for gynoecy in bitter gourd (Momordica charantia L.) was undertaken with an objective to develop stable gynoecious inbred lines in bitter gourd through selection from sib mated and crossed population involving gynoecious female parents and maintain gynoecy through hormonal regulation and micropropagation. The study was carried out at Department of Vegetable Science, College of Horticulture, Vellanikkara, during the period of 2017-2019. The gynoecious line (KAU-MCGy-101) identified from the Kerala Agricultural University was tested for stability of the gynoecious sex expression. The sib mated gynoecious inbred along with the F1 hybrid (KAU-MCGy-101 × Preethi) developed by crossing with monoecious variety ‘Preethi’ were subjected to morphological characterization and evaluated for biometric characters and genetics of sex expression. For maintaining and fixing the gynoecious trait, micropropagation was attempted through shoot tip culture. Hormonal regulation for the maintenance of gynoecy using various concentrations of silver thiosulphate (STS) was also studied.
The results revealed the stability of gynoecious sex expression in the inbred (KAU-MCGy-101), as all the plants resulted from sib mated population produced only female flowers throughout the growth phase. The gynoecious inbred exhibited early bearing of female flowers at lower nodes compared to the F1 hybrid. Moreover the inbred exhibited higher average fruit weight, fruit length and girth compared to early reported gynoecious lines. Hence the gynoecious inbred, KAU-MCGy-101 holds enormous potential for future breeding programme for earliness and yield in bitter gourd. The sib mated gynoecious inbred and F1 hybrid were evaluated for qualitative characters and they differed for colour of fruit skin and fruit bitterness. All the sib mated gynoecious plants produced dark green colour spindle shaped fruits which were strong bitter in nature, whereas, the fruits of F1 hybrid were light green in colour with spindle shape and moderate bitterness.
Genetic analysis for sex expression confirmed the recessive nature of gynoecy in bitter gourd since there was no segregation for the gynoecious character in the sib mated gynoecious inbred and F1 hybrid.
Micropropagation protocol for maintenance of gynoecious bitter gourd lines through in vitro shoot tip culture was standardized. Direct organogenesis was observed in the MS medium supplemented with BA alone and in combination with NAA. MS medium fortified with 2.0 mgl-1 of BA alone was found to be suitable for better and faster shoot initiation. Multiple shoot induction was observed in shoot initiation medium added with BA alone and maximum number of shoots per explant was achieved with higher concentration of BA (2 mgl-1). For in vitro shoot elongation, MS medium supplemented with 0.5 mgl-1 IAA and 0.5 mgl-1 NAA performed best. In vitro rooting response was found to be enhanced with the addition of activated charcoal in the medium along with IBA. Half strength MS medium combined with 1.0 mgl-1 IBA and 3.0 gl-1 activated charcoal exhibited early rooting, maximum rooting response (100%) and more number of roots. While evaluating the regenerated plants after hardening, 70.58 per cent survival per cent was recorded. All the regenerated plants were gynoecious in sex expression.
Effect of various concentrations of STS and stage of application in inducing maleness in gynoecious bitter gourd was studied. STS in general induces male flowers in cucurbits through the activity of silver ions. However in the present study, all the treatments of STS induced hermaphrodite flowers instead of male flowers. Single spray of STS at 200 ppm after the first female flower emergence was found to be the best, as it was superior in terms of total number of hermaphrodite flowers produced. Application of STS at the later stage after the emergence of first female flower is equally effective in inducing hermaphrodite flowers when compared to double application, one at two-four leaf stage and other at later stage, which has enormous significance in the exploitation of gynoecy for crop improvement in bitter gourd
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