Diagnosis of Fungal Diseases of Plants

Abstract

Crop plants are infected by numerous fungal pathogens from seedling stage to the seed maturing stage under the natural conditions, either singly or in combination with other kinds of microbial plant pathogens. Diagnosis of the ­disease problem observed for the first time, involves isolation of the fungi in pure cultures using appropriate media and identification of the putative pathogen based on ­morphological, physiological/biochemical, immunological and genomic nucleic acid characteristics, followed by inoculation onto the natural plant host for reproducing the symptoms observed earlier. The characteristics of the fungus reisolated from the inoculated plants are then compared with original description of the fungus isolated from the diseased plants earlier. Adoption of all steps in Koch’s postulates is essential. Precise identification of the pathogens up to subspecies, varieties, races/biotypes of the fungal pathogen species is accomplished by applying immunological and/or nucleic acid-based techniques. Correct diagnosis of the disease (s) is considered to be the corner stone of the development of effective management of the disease concerned. The need for establishing disease diagnostic centers and the role of plant quarantines in preventing the introduction of new plant diseases and principle of certification of seeds and propagative plant materials to reduce disease incidence and spread is highlighted.