Journal of Biology, Agriculture and Healthcare www.iiste.org ISSN 2224-3208 (Paper) ISSN 2225-093X (Online) Vol.3, No.19, 2013 50 Impact of Epidemiological Factors on Development of Puccinia Triticina Sp. Tritici on Wheat in Pakistan Adnan Riaz 1* , Abid Riaz 1 , Atiq Ur Rehman Rattu 2 , Muhammad Ibrahim Tahir 1 , Muhammad Azeem 3 , 1 Department of Plant Pathology, Pir Mehr Ali shah Arid Agriculture University, Rawalpindi, 46300, Pakistan. 2 Crop Disease Research Programme, National Agricultural Research Center, Islamabad, 44000, Pakistan. 3 Department of Soil Science, Pir Mehr Ali shah Arid Agriculture University, Rawalpindi, 46300, Pakistan. * Corresponding author. Adnan Riaz E-mail:adnandani22@gmail.com Abstract 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. Introduction Climate change affects wheat crop, a rich source of carbohydrates, fats, proteins and dietary fibers, that contributes 21% of food and 200 million hectares of land, cultivated worldwide (Ortiz et al., 2008). In Pakistan in 2009-10, wheat was cultivated on an area of 9.042 million hectares with an annual production of about 23.864 million metric tons (GOP, 2010). Wheat production is severely affected by abiotic and biotic stresses (Singh et al., 2008) like leaf and stripe rust are a constant threat to wheat production in Asia and all over the world (Singh et al. 2005; Chen, 2005). The leaf (Puccinia triticina) rust is the most widespread of three types of rusts over large geographical areas caused significant yield losses in wheat production worldwide (Kolmer 2005; Bolton et al., 2008). In Asia, leaf rust affects approximately 60 million hectares i.e., 63% of production, if susceptible cultivars are grown (Singh et al., 2005). Quality losses due to leaf rust include reduced protein levels and softness equivalent scores (Everts et al., 2001). In Pakistan, leaf rust epidemics caused great yield losses in wheat production in 1973 and 1978 (Hassan et al., 1973; Hussain et al., 1980). The leaf rust of wheat appears on wheat during anthesis period (Rattu et al., 2010). The combination of inoculum (urediniospores), favorable environment and susceptible host plants results in the development of disease epidemics (Duveiller et al., 2007). The disease is favored by three important weather factors that are moisture, temperature and wind (De- vallavieille-Pope et al., 2002; Wiik and Ewaldz, 2009). Thus, influencing the severity and frequency of leaf rust epidemics (Shaw et al., 2008; Chakraborty et al., 2010). Moisture affects spore germination, infection, and survival of the urediniospores, requires at least 3 hrs of continuous moisture on the plant surfaces to germinate and infect plants (Bolton et al., 2008). Temperature affects spore germination, infection, latent period, sporulation, spore survival, and host resistance. The pathogen requires a favorable temperature ranging between 10-30 o C (Singh et al., 2002; Bolton et al., 2008) and free water on the leaf surface (Bolton et al., 2008).Wind can affect drying of urediniospores of P. triticina that results in reduction in on-site germination and infection. It also increases the duration of spore viability and plays a major role in the spread of leaf rust (Chen, 2005). This changing climate ultimately affects the wheat production, generate food security issues and influence plant disease epidemics. Accordingly the objectives were to study the effect of weather changes on development of wheat leaf rust in Pakistan, and find an appropriate relationship between leaf rust severity on wheat cultivars with meteorological data. Materials and Methods Collection of disease data: Leaf rust data of six wheat cultivars (Morroco, Inqilab-91, Sarsabz, Tandojam-83, Soughat-90 and Kirin-95) from 2003-2009 was obtained from Crop Disease Research Programme (CDRP), National Agricultural Research Centre (NARC), Islamabad. The disease data was of three locations viz., Faisalabad (31°15′N73°03′E), Bahawalpur (29°23′44″N71°41′1″E) and Sakrand (27.08°N 68.16°E). The leaf