Genetic diversity in male and female landraces of teasel gourd in north-eastern India and strategies for crop improvement through induced monocliny.

Background: Teasel gourd is an important, indigenous, vegetatively propagated, high-value, underutilized cucurbit vegetable crop grown in South and Southeast Asia. Due to its wider adaptability, it is grown from plains to mid-hills. The crop is lacking in research, primarily related to the extent of genetic diversity in the region and crop improvement, which is further constrained by dioecism. To assess the genetic diversity in male and female populations of teasel gourd based on morphological traits and microsatellite makers and the response of AgNO₃ to induce monocliny, seventy genotypes, including eight males, were collected from different regions of the Northeastern states of India.

Results: Under evaluation trials, wider variability was observed for leaf, flower, and fruit characteristics. Traits: ovary length ranged from 0.58 to 1.23 cm, fruit length 4.76 to 11.23 cm, fruit diameter 3.0 to 3.13 cm, fruit weight 22.8 to 129.3 g, and 100 seed weights 12.60 to 36.3 g, reducing sugar 2.99 to 7.39%, and vitamin-C content from 44.80 to 79.68 mg/100 g. The fruits and quality attributes have also shown high heritability (> 60%) and genetic advance (> 20%). Under molecular analysis, out of 43 microsatellite markers, 40 were polymorphic, and the polymorphism information content (PIC) ranged from 0.08 (Sed-09) to 0.68 (McSSR-5). A moderate genetic diversity was observed in the male and female genotypes based on gene diversity, PIC, and Nei's genetic distance. The additive main effects and multiplicative interaction (AMMI) analysis of variance for fruit traits has shown a significantly higher contribution of the genotype, followed by the genotype × environment interaction. Based on multi-trait stability index analysis for fruit traits, genotypes MNTGC-2, MNTGC-1, MNTGC-4, MZTGC-1, and ASTGC-3 were the most stable. Foliar application of AgNO3 at 500 mg l^- 1 was best for inducing hermaphroditism in female genotypes. The pollen germination can be enhanced to 82.3% over the control (23.1%) by the application of nutrient media comprised of sucrose (15%), boric acid (25 mg l^- 1), and calcium nitrate (25 mg l^- 1).

Conclusions: The available diverse genetic resources in teasel gourd can be effectively utilized by selecting stable superior genotypes, crop multiplication by selfing in superior induced hermaphrodite genotypes and exploiting heterosis by mating among diverse genotypes using silver nitrate.