Pathobiology of Foliar blights of Wheat in Punjab and NWFP Areas of Pakistan

Abstract

Wheat occupies a position of paramount importance amongst worlds crop plants both in extent of area and magnitude of food production. Being a staple food, it has been ranked as the most important crop for food security in Pakistan. Foliar pathogens other than rusts and mildews are considered to contribute significantly to the low average yields of cereal crops in many developing countries. Foliar blight can often lead to the total loss and fanners are becoming more and more aware of such diseases in different agI'o ecological zones of the world. The foliar blight has been recorded in most growing areas of India, Bangladesh and Nepal. During a survey in spring 2000, the pathogens responsible for foliar blight were observed in different frequencies in various districts of Punjab. The fungi isolated were Alternaria alternata, Stemphylium spp., Cladosporium spp, Pyrenophora tritici-repentis and Bipolaris sorokiniana. In Pakistan there are limited reports and research work on foliar blight, therefore for ClllTent studies approaches are made to analyze the situation of pathogens responsible for foliar blight in different agro ecological wheat production zones. Another purpose of the study was to observe the phenotypic characterization and aggressiveness analysis of the pathogen involved in foliar blight. Surveys in the different agro-ecological zones of wheat growing areas of Punjab and NWFP were carried out during 2004 &2005 to ascertain the prevalence, incidence and disease severity of foliar blight. Fungi were isolated from foliar samples. The phenotypic characterization of the isolates was made by measuring the size of the spores under microscope and on the basis of colour of the culture and type of growth of the fungus. One method (among five methods) for pathogenicity and aggressiveness analysis was standardized by using different protocols. Aggressiveness analysis of eighty seven isolates of Bipolaris sorokiniana was conducted on three commercial wheat varieties and a preliminary epidemiological study which include suitability of temperature of different isolates collected from different ecologies and hosts of the pathogen other than wheat were conducted.