Antixenosis Studies in Different Genotypes of Bitter Gourd Fruits against the Infestation of Melon Fruit Fly

In crop plants, three principle mechanism viz., non-preference (antixenosis), antibiosis and tolerance are responsible for imparting resistance to insects. Non preference denotes a group of plants character and insect response that keep away the insect from using a particular plant or variety for oviposit ion, food, shelter, or combination of both. Keeping in this view, seventy four promising genotypes of bitter gourd were screened against fruit fly infestation to identify the antixenosis traits involved in host plant selection by the melon fruit fly. On the basis of percent fruit infestation and the average number of larvae per damage fruit, the genotypes were categorized in to different groups i.e. (Highly resistant, resistant, moderately resistant, susceptible, and highly susceptible). The fruit infestation during the 2006 and 2007 summer season (Average of two years) ranged from 13.23% to 83.75%. Larval density per fruit ranged from 2.59 to 8.13 larvae per fruit. The larval density increased with the increase in percent fruit infestation and showed significant positive correlation (r = 0.98).The depth of ribs in resistant genotypes was higher as compared to susceptible genotypes. The number of seed was recorded maximum in the genotype VRBT-96 (31.8) and minimum was recorded in the genotype IC 68314(14.8). The fruit toughness had significant negative effect on fruit infestation(r = -0.52) and larval density (r = -0.57) of fruit fly. There was a strong correlation between number of ribs and fruit toughness, and these traits can be used as markers to select bitter gourd genotype resistant to melon fruit fly.