Ecology and Epidemiology of Wheat Blast

Abstract

Wheat blast, caused by the fungal pathogen Magnaporthe oryzae pathotype Triticum, is a serious threat to wheat production, causing losses that can vary from meagre to almost 100%. The disease can attack all aboveground parts of the plant; however, severe spike infection can be observed with very little infection on the leaves or culms. The blast pathogen attacks the base or upper part of the rachis affecting spike formation that makes the spike partial or completely bleached or sterile resulting in shrivelled or no grains. Potential sources of primary inoculum for disease development are the infected wheat seeds, crop residues and infected wheat stubble, and conidia from grass species other than wheat where the fungus overwinters. Other steps in the disease cycle are still not very well known. Moreover, limited data are available on the environmental determinants for optimal wheat blast infection. Nowadays, it is known that the intensity of the damage caused by wheat blast is directly proportional to the level of rainfall during the heading stage of wheat. A combination of high temperatures, excessive rain and long and frequent leaf wetness has favoured the occurrence of this disease. These factors must be taken into account when establishing a system to predict the intensity of the disease in a certain area of cultivation.