Characterisation and aggressiveness of tomato early blight fungus (Alternaria solani) in Limpopo Province

Abstract

Among the fungal diseases infecting tomato crop, early blight caused by Alternaria solani (Ellis & G. Martin) is one of the most destructive fungal foliar diseases. The aim of this current study was to document the prevailing pathogenic diversity of A. solani populations in Limpopo based on morphological characteristics, fungicide sensitivity, and aggressiveness of A. solani isolates. The tested isolates were collected from four different areas across different tomato production sites in the Limpopo Province and pathogen isolations were carried-out under laboratory conditions. The the morphological variation of different A. solani isolates was evaluated. The results obtained in this study show that A. solani isolates exhibit high variations in mycelial pigmentation, number of septa, beak length and colony diameter. The current study also evaluated the sensitivity of A. solani isolates obtained from different areas in the Limpopo to commonly used fungicides. All the tested fungicides (chlorothalonil, copper oxychloride and mancozeb) reduced the mycelial growth of A. solani isolates, even at lower concentrations. However copper oxychloride fungicide provides better inhibition of mycelial growth as compared to other tested fungicides. Furthermore, the aggressiveness of the different isolates was investigated using Money-maker and Rodade tomato cultivars. The results obtained in our, study revealed that isolates from different areas differed in terms of their level of aggressiveness on both cultivars. However, all the tested isolates were aggressive in their ability to cause early blight in both cultivars. There was a difference on how both cultivars responded to isolates from different areas with the Money-maker being highly susceptible to all the tested isolates as than the Rodade Key words: Aggressiveness, Alternaria solani, Fungicide sensitivity, isolates, Limpopo Province, Morphological characterization, susceptible tomato cultivars.