Diversity of Pathotypes of Leaf Rust (<i>Puccinia triticina</i>) Pathogen in Wheat Crop in Nepal

Wheat (Triticum aestivum) is third most important crop in Nepal after rice and maize. The area of cultivation of wheat is increasing compare to last decade but its productivity could not be increased significantly due to many biotic and abiotic factors. Among them, rust disease is major biotic constraint. Leaf rust (Puccinia triticina) is an economically important disease which occurs on major wheat growing areas of plain and hill of the country. The leaf rust disease monitoring and samples collection were done from 32 districts across the wheat growing area. Rust infected leaves were folded such that rust pustules preserved inside without destroying spores. Excess leaf moisture was removed by keeping them in room temperature with shade drying. Proper dried samples were kept in paper envelop and diagnosed pathotypes at Indian Institute of Wheat and Barley Research (IIWBR), Indian Council of Agricultural Research (ICAR), Regional Station, Flowerdale, Shimla, India. urediospores were revived on 2% water agar and multiplied in susceptible host Agra Local. The fresh urediospores of each sample was collected from susceptible host and inoculated on 5-7 days old seedlings of the standard differential sets. The pathotypes of pathogen was diagnosed on the base on disease infection type showed in the differential sets. Pathotypes 57R39 121R63-1, 21R55, 109R31-1, 121R60-1, 93R15 and 93R39 were commonly observed in both plain and hills. Similarly, the pathotypes 125R23-1, 109R63 and 21R63 were recorded in lower belt whereas, pathotypes 5R13, 49R39, 125R28, 21R31 and 93R47 were found only at hilly regions. The pathotypes 21R55, 121R63-1, 121R63-1and 5R37 were recorded in successive years in most of the wheat growing area. Twenty one different pathotypes of P. triticina occur in different parts of the country. The evolving of different pathotypes diversity of pathogens may be caused by selection pressure due to same genetic materials of wheat genotypes grown in the country and conducive environment. Hence, monitoring rust pathotypes is a one of the necessary step for successful planning to manage the rust disease by developing resistant wheat genotypes.