Bio-physical bases of antixenotic mechanism of resistance in ridge -gourd [Luffa acutangula (L.) Roxb.] Cucurbitacae) against fruit fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae)
Sanjiv Duradundi, J Jayappa, YK Kotikal, Gangadhar N and AM Nadaf
Plant genotypes possess different phenotypic and/or biochemical properties, which resultantly induce in them different mechanisms of resistance. These mechanisms enable the plants to avoid, tolerate or recover from the effects of insect pest attacks. An investigation on screening of ridge gourd [Luffa acutangula (L.) Roxb.] genotypes against fruit fly, Bactrocera cucurbitae (Coquillett) was undertaken during the year 2013-2014 at the Department of Entomology K.R.C. College of. Horticulture, Arabhavi, Karnataka. The results of the present studies revealed that there was significant variation in tested Ridge-gourd genotypes for percentage fruit-infestation and larval-density per fruit. KRCCH-1 and Amoha were highly resistant and resistant genotypes respectively and identified as a resistance source for fruit fly, Bactrocera cucurbitae. The larval density per fruit had a significant positive correlation with percentage fruit infestation. The fruit-length, fruit diameter, number of longitudinal ribs/fruit and number of small ridges/cm2, which were significantly lower in resistant and higher in susceptible genotypes, had a significant positive correlation with the percent fruit infestation and larval-density per fruit. However, fruit toughness, height of small ridges, height of longitudinal ribs and pericarp thickness, which were significantly higher in resistant and lower in susceptible genotypes, showed significant negative correlation with the percent fruit infestation and larval-density per fruit. Step-wise multiple regression analysis indicated that the tested biophysical fruit traits explained 100 percent of the total variation in fruit fly infestation. The fruit width, fruit, length, depth of longitudinal ridge and toughness explained 89.6 percent of the total variation in fruit infestation by fruit fly. The maximum variation in fruit infestation was explained by width of the fruit (31.50%) followed by depth of longitudinal ridges (24.31%), length (17.36%) and toughness of the fruit. Other two explained only less than 11 percent total variation in fruit infestation by fruit fly.These can be used as marker traits for selection of fruit fly resistant genotypes of ridge gourd.