Effect of environmental conditions on the growth of Cryptosporiopsis spp. causing leaf and nut blight on cashew (Anacardium occidentale Linn.)

Abstract

A new disease (cashew leaf and nut blight) in Tanzania caused by a fungus related to the genus Cryptosporiopsis was identified in 2006. The present work investigated the effects of environmental factors on the growth of Cryptosporiopsis spp. causing blight on cashew. The mycelial growth, colony character and sporulation pattern of 10 fungal isolates, grown on seven different culture media namely, corn meal agar (CMA), malt extract agar (MEA), tryptone dextrose agar (TDA), potato carrot agar (PCA), water agar (WA), potato dextrose agar (PDA) and host leaf agar were observed after 10 days of incubation at 25±2°C. The colony diameter, culture characteristics and sporulation of the 10 isolates were greatly influenced by the type of growth medium used. The best mycelial extension was recorded in 12 h alternating light/dark followed by total light and total dark conditions, respectively. Seven media were evaluated for best growth of the fungi that is, Cryptosporiopsis spp. grew maximum on WA followed by host leaf extract media and PDA, respectively but least grew on the TDA medium. The growth of Cryptosporiopsis spp. was maximum in temperature range of 25 to 30°C. The most suitable pH level for growth of fungus was 7.0 and 6.0. These results will be useful for fungal taxonomic studies. Key words: Cryptosporiopsis spp., culture media, light, temperature.