Culture Media Options for Growth and Morphological Characterisation of Cercospora coffeicola Affecting Coffee in Zimbabwe

Abstract

Cercospora leaf spot is fast turning into a critically important diseasein Zimbabwe. The disease is caused by Cercospora coffeicola whichsignificantly reduces productivity and quality of coffee. Disturbingly,optimum sporulation of Cercospora coffeicola in culture remains a limitingfactor for microbial analysis and quantitative studies of Cercosporaleaf spot. Faced with this challenge, an in-vitro study was conducted atCoffee Research Institute, Manicaland, Zimbabwe to examine growth ofCercospora coffeicola in different nutrient media and to determine the bestmedia for Cercospora coffeicola analysis. Six nutrient media were assessed(corn meal agar, oat meal agar, Czapek Dox agar, malt extract agar, yeastextract agar and potato dextrose agar) for the growth of Cercosporacoffeicola. The laboratory-based experiment was duplicated, laid out ina Completely Randomized Design, replicated three times and based onCercospora coffeicola nutrient inoculation. Data were collected on radialgrowth, colour and texture of mycelium at 3 and 6 days after inoculation.There were significant differences (p < 0.05) in the growth of Cercosporacoffeicola in media after 3 and 6 days. Malt extract agar had the greatestradial growth (34 mm and 32 mm) of Cercospora coffeicola for trials 1and 2 respectively, whilst the least growth was in the oat meal agar (14.2mm and 15.7 mm) for trials 1 and 2 respectively. There were variations incolour and texture of mycelium with malt extract agar, potato dextrose agarand oat meal agar associated with darker colours and rough texture whilesmooth white mycelia were found in corn meal agar. After considering allnutrient media, malt extract agar was found to be the best media for thegrowth of Cercospora coffeicola in-vitro. On the basis of our findings, theauthors recommend the use of malt extract agar as the primary media foridentification and characterisation of Cercospora coffeicola.