Impact of Epidemiological Factors on Development of Puccinia Triticina Sp. Tritici on Wheat in Pakistan

The weather changes after the host-pathogen interaction play a vital role in the wheat leaf rust development. This study presents the impact of weather changes at wheat growing areas of Faisalabad, Bahawalpur and Sakrand  on development of wheat leaf rust  by taking into account the disease and weather data (from 4 th February -5 th March) of the respective years from 2003-2009. For the purpose multiple regression analysis of the temperature, relative humidity and wind velocity with the disease severity on six wheat cultivars namely Morroco, Inqilab-91, Sarsabz, Kirin-95, Soughat-90 and Tandojam-83 was conducted. It was found that temperature and relative humidity both played a significantly positive effect in disease development while wind velocity had negative impact on disease development. The most favorable conditions for leaf rust development on wheat in Pakistan were recorded at Bahawalpur, where the temperature (16.85-20.44°C), relative humidity (57.08-76.95%) and wind velocity (1.98-4.07 km/hr) acts collectively in onset of leaf rust. When these weather parameters were individually regressed no clear trends were noticed keeping in view their coefficient of determination (R 2 ), regression coefficients/lines. This study depicts that all these factors interact with each other in a multi-colinear interaction, and had a collective effect on onset of leaf rust in the natural environment. Key words: Climate change, wheat, leaf rust, weather parameter.