Impact of heat stress on Fusarium wilt (F. solani) incidence in cultivated tomato and related species

Abstract

The incidence of Fusarium wilt on tomato is increasing with rising global temperatures. To assess the impact of this disease, a factorial experiment of ten tomato genotypes grown at two temperatures and two levels of disease severity was established using hydroponics in a poly tunnel house. Fusarium wilt inoculum was used to promote disease and the heat treatment produced temperatures > 40°C for most of the growing season. Genotypes varied significantly for disease incidence and response to heat stress. Significant temperature x disease treatment interactions were observed for number of inflorescences per plant (IPP), fruit set ratio (FSR), number of fruits per plant (FPP), fresh fruit weight (FFW), plant dry weight (PDW) and disease severity index (DSI). A highly significant correlation (R2 = 0.98) was observed between disease incidence under both control and high-temperature treatments, even though the treatments were significantly different. Biomass was reduced under both heat and disease stress and was correlated across treatments (R2 = 0.86). The genotype LA3847, characterized by relatively low fruit set inhibition and high fruit yield, was classified as tolerant to both heat and disease stress. Concurrent selection for improved disease and heat tolerance appears possible as the disease severity index and the heat stress response were not correlated (R2 = 0.11).