Influence of climatic determinants and Host shift on Genetic diversity and population structure of oriental fruitfly Bactrocera dorsalis Hendel

Abstract

India (82.631 million tonnes) ranks second in the production of fruits and vegetables globally followed by China (154.364 million tonnes) (Government of India (2012-2013), Economic survey). Prevalence of different agro-climatic conditions has made it possible for the production of large amounts of fruits of tropical, subtropical and temperate origin. The annual production of fruits has grown faster than vegetables and India leads in the production of following fruits viz., mango (40%), banana, pomegranate, sapota, grapes and anola (30%) (Sandeep Sachdeva et al., 2013). Though India is the largest producer of fruits, it exports lt1% of its production due to insect pest quarantine issues. Of these, true fruit flies are one of the major quarantine pests in the tropics, which cause extensive losses to varied fruit crops.Considering the economic importance of tephritid fruit flies, over the few decades in India, many studies have tried to explain the ecological basis for their abundance and geographical distribution (Verghese et al., 2006). Many reports have indeed focused on the bioecology of the key species such as B. dorsalis, Bactrocera zonata (Saunders) Bactrocera cucurbitae (Coquillet) and B. invadens. Often in these studies, a high correlation of fruit fly abundance with temperature has been observed allowing the assessment of population structure in different zones and seasons (Kamala Jayanthi and Verghese, 2011; Kamala Jayanthi et al., 2011; Arthikirubha et al., 2017). Sukhla and Prasad (1985) determined the key biotic and abiotic factors that support the survival of fruit flies (Dacus dorsalis) as host availability, median temperature and relative humidity. Considering the polyphagous nature of B. dorsalis and its wide geographical distribution across the agro-ecological zones, understanding its population structure and the associated genetic diversity in relation to its newlinehost shift and climatic variables is crucial and forms the basis for the development of sustainable management options for the farmers at orchard level.The decline in the quality and quantity of mango fruits in orchards is mainly attributed to fruit fly infestations that cause severe economic losses to small and marginal farmers. However, the magnitude of economic losses that are being incurred at farm level due to fruit fly infestation is not yet clear. Particularly in India, the control of fruit fly infestation is not achieved completely due to the fragmented land holdings and lack of awareness about the area-wide management concept among the farmers. Further, the climate changing scenario and availability of different host fruits for fruit fly survival across the calendar year causes enormous losses to mango crop. Hence, there is a need to study the influence of climatic variables and host shift patterns on the fruit fly population structure which may possibly help ecologists to strategize the controlling measures to help the farming community. newline