Field screening of different genotypes of bitter gourd for infestation with the melon fruit fly, Bactrocera cucurbitae (Coquillett) in two agro-climatic zones of West Bengal, India

Bitter gourd (Momordica charantia L.) also known as bitter melon being rich in folate and vitamin C is one of the most popular cucurbitaceous vegetables grown extensively in the tropics and subtropics especially in India. Besides its numerous culinary preparations, it has immense medicinal properties as well as ornamental uses. The fast growing vines and creepers of bitter gourd attract a number of insect pests of which fruit fly (Bactrocera cucurbitae Coq.) is the most destructive due to difficulties associated with its chemical control as the maggots remain and feed inside the fruits, protected from direct contact with insecticides. Therefore, exploration of alternative control measures for this pest is crucial and identification of promising resistance genotypes could be the effective option. Considering the above aspects in view, twenty five genotypes of bitter gourd (M. charantia L.) were preliminary screened under field condition to study their susceptibility against the infestation of melon fruit fly, B. cucurbitae (Coq.) in two agro-climatic zones of West Bengal, India. Based on the performance of preliminary screening, nine genotypes were selected for final screening. The experiment on preliminary screening was conducted at Kalyani, Nadia (Gangetic Alluvial zone) and Sekhampur, Birbhum (Red and Laterite zone) during spring-summer season of 2016 and 2017 while the final screening was done in 2018. Results of the study revealed that percent fruit infestation and larval density per fruit varied significantly in all the tested genotypes and none of the genotypes were free of infestation with B. cucurbitae. During preliminary screening, the pooled data of mean percent fruit infestation of two years at two locations showed that infestation of melon fruit fly was significantly lower in the genotype US-6214 (14.50%) with larval density of 3.63 larvae per fruit followed by Meghnad-2 (16.50% and 4.08 larvae per fruit). Highest mean percent fruit infestation was recorded in the genotype Pusa Do Mausami (69.67%) with larval density of 10.77 larvae per fruit followed by Diamond Bolder (60.67% and 8.13 larvae per fruit) and were categorized as susceptible. Out of the twenty five genotypes of bitter gourd tested, six genotypes were classified as resistant, eleven genotypes as moderately resistant and eight genotypes as susceptible against melon fruit fly infestation. The mean data of the final screening at two locations revealed that US-6214 and Meghnad-2 recorded significantly low percent fruit infestation (14.35% and 16.33%) with 3.85 and 4.37 larvae per fruit while Pusa Do Mausami had the highest infestation and larval density (63.67% and 10.36 larvae per fruit). These findings suggest that US-6214 and Meghnad-2 may be utilized in resistance breeding programmes against melon fruit fly.