USE OF CORRELATION ANALYSIS FOR THE STUDY OF ANTHRACNOSE ON AVOCADOS AND MANGOES IN SOUTH AFRICA

A market survey was conducted to determine the incidence of stem-end rot (SE) and anthracnose on “‘Fuerte’” avocado fruit and SE, anthracnose and soft brown rot (SBR) on “‘Sensation’” mango fruit from the most important production areas in South Africa. Two hundred and ninety Colletotrichum gloeosporioides isolates from these lesion types were compared using fruit inoculations, morphological and physiological characteristics. Factors such as geographical area of origin and symptom, from which original isolations were made, could not be correlated with lesion development on these hosts. Morphologically, South African isolates of C. gloeosporioides were as variable as isolates from over the world. Conidial length varied considerably, but width remained relatively constant. No correlation was found between the length:width ratio of conidia and virulence of isolates when inoculated into avocado and mango fruits. However, there was a correlation between virulence and conidial shape. C. gloeosporioides isolates differed in growth rate and a correlation was evident between growth rate and virulence towards avocado fruits.