Evaluation of aggressiveness of Alternaria solani isolates to commercial tomato cultivars

Abstract

Early blight caused by Alternaria solani is the most limiting factor in tomato production in South Africa and globally. This study was carried out with the aim of assessing the aggressiveness of 32 Limpopo A. solani isolates on two selected susceptible tomato cultivars namely, Money-maker and Rodade using leaf disc assay and greenhouse inoculation methods. There was a significant (p ≤ .05) difference among tested isolates based on collection area. Varying results were also observed on same isolates tested under laboratory and greenhouse conditions. The highest disease severity of 83.94 and 100% was recorded in the greenhouse and leaf disc experiments, respectively, on isolate V11 and the lowest disease severity of 20.01 and 56.70% was recorded in isolate B2 on both cultivars in the greenhouse and leaf disc experiments, respectively. The results obtained in this study revealed that A. solani isolates from different areas in Limpopo differed in their level of aggressiveness on both cultivars. Our findings demonstrate the possibility of the development of new A. solani strains that are more aggressive and virulent toward the commercial tomato cultivars.