GROWTH RESPONSE OF DIFFERENT FUNGI PATHOGENS UNDER FLOODED CONDITION

Abstract

Climate change is a long-term shift in temperature and weather patterns of the earth. These shifts may be natural, such as through variations in the solar cycle, it can also be influenced by human activities. Climate change brings about environmental stresses like increased flooding which may affect living components of the ecosystem. Frequent flooding due to climate change affects infection by a number of fungal plant pathogens. Thus, this study was initiated to carryout in vitro studies on the effect of excess water on the growth of some fungal pathogens. Malt extract and potato dextrose agar were used to culture the fungal isolates from fruits of tomato, lemon and potato tubers. The isolates were flooded for different durations (24 hrs, 48 hrs, 72 hrs, 96 hrs and 120 hrs) and the growth was observed thereafter. The result showed that excess water increased the growth of some fungal pathogens while the growth of others were inhibited. After flooding there was neither decrease nor increase in the mycelial extension of Aspergillus giganteus and Lasiodiplodia theobromae. There was an increase on the mycelial growth of Geotrichum candidum, Fusarium solani, on both malt extract Agar (MEA) and potato dextrose agar (PDA). There was a decrease in the mycelial growth of Trichoderma sp. and Penicilium digitatum on malt extract agar. Also the result showed that some of the fungi behaved differently on different media after flooding. After flooding, the mycelial growth of Penicilium digitatium increased on potato dextrose agar plates while there was a decrease on the mycelial extension on malt extract agar plates. For Ascochyta sp., there was an increase in the mycelial extension on potato dextrose agar plates in comparison with malt extract agar. There was also an increase in the mycelial extension of Aspergillus niger on malt extract agar plates while a decrease was observed on potato dextrose agar plates. This study has revealed the behaviour of the fungi isolates used under flooded condition, in which growth could be affected positively or negatively depending on the fungus in question. This study has also revealed that growth medium has marked influence on the growth of fungi. Subsequent development of disease by the fungi may therefore be host dependent after a flood.