Buckeye rot of tomato in India: Present status, challenges, and future research perspectives

Abstract

Tomato in India is commonly exposed to various diseases of fungal, bacterial, and viral origin, resulting in substantial yield losses (≥50%). Buckeye rot (caused by Phytophthora nicotianae var. parasitica) is among the major constraints in the successful cultivation of tomato crops in various parts of the world including the Solan district of Himachal Pradesh state, India. The fruit rot becomes more devastating under high humidity and wet soils. Symptoms generally appear on green fruit as alternate dark and light brown concentric rings. The genome size of P. nicotianae var. parasitica is 82 Mb with >23,000 predicted genes. High humidity (> 60%) and optimal temperatures (20-25 ºC), along with rainfall (≥ 10 mm), help to disperse the pathogen as the inoculum reaches the fruit through splashing rains. Sporangia germinate indirectly by producing zoospores at 20-25o C, or directly via germ tubes at >25ºC. In the absence of suitable resistant varieties, no single management practice is sufficient to keep the disease below the economic threshold level; therefore, integration of cultural and chemical methods is preferable. This paper aims to focus on the etiology, and management challenges of buckeye rot. We recommend innovative disease management strategies like identification and deployment of resistant cultivars as well as spraying of synthetic chemical fungicides, biocontrol agents, and use of abiotic chemicals that induce resistance, for developing sustainable crop production practices.