An emerging threat of Phytophthora infestans causing late blight of tomato in Uttar Pradesh, India

摘要

Tomato (Solanum lycopersicum) cultivation in India has expanded to 0.91 million ha in 2015-2016. Farmers originally cultivated this crop for self-consumption but now are adopting it as a cash crop for commercial production. Recently, the occurrence of late blight on tomato, caused by Phytophthora infestans, in Uttar Pradesh, India has appeared to increase but average late blight incidence on tomato has not been well documented for this region. In early 2016, a severe outbreak of late blight was observed in tomato with a disease incidence up to 60% in farmers' fields in eastern Uttar Pradesh and at the IIVR Research Farm in Varanasi, also in eastern Uttar Pradesh. Initial disease symptoms appeared on leaves as irregular, water-soaked and light-brown lesions usually covered with white, cottony mycelial growth on the underside of the leaf (Fig. 1). Water-soaked brown lesions expanded rapidly on stem and green fruits. Infected green fruits often developed olivaceous, brown-coloured, leathery, hard structures (Fig. 2). All infected fruits eventually fell off the plants and could not be marketed or used for human consumption.