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Pak. J. Bot., 42(1): 401-407, 2010.

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PREDICTION OF YIELD LOSSES IN WHEAT (TRITICUM AESTIVUM L.) CAUSED BY YELLOW RUST IN RELATION TO EPIDEMIOLOGICAL FACTORS IN FAISALABAD

S. AHMAD*, M. AFZAL, I.R. NOORKA, Z. IQBAL, N. AKHTAR,   Y. IFTKHAR AND M. KAMRAN

Abstract: Thirty six genotypes were screened against yellow rust to check their level of susceptibility or resistance. Among 36 genotypes screened against yellow rust, 18 were susceptible, 6 were moderately susceptible to susceptible, 7 were moderately resistant to moderately susceptible and 5 genotypes remained resistant. Yield losses were predicted in wheat on the basis of varying level of yellow rust severities. It was observed that susceptible genotypes showed higher yield losses as compared to resistant genotypes. Maximum severity of 90% of yellow rust resulted in 54% to 55% calculated and predicted losses, respectively. While 40, 50, 60 and 70% disease severity of yellow rust caused 35-34%, 38-37%, 42-40% and 46-47% calculated and predicted losses, respectively. However, the decline in losses was observed as the genotypes changed their reaction from susceptible to moderate susceptible. Similarly, losses were diminished as the varieties/lines showed moderate resistant reaction from moderate susceptible. Minimum temperature and relative humidity remained positively correlated while the maximum temperature showed negative correlation with stripe rust severity. With the increase of minimum temperature and relative humidity a rise up in stripe rust infection was seen while as the maximum temperature increased stripe rust infection decreased on different genotypes. It may be concluded from the study that environmental factors played major role in the spread of the disease which result in yield losses.

¹University College of Agriculture, University of Sargodha, Sargodha, Pakistan. Corresponding author, E.mail address: sal_uaf@yahoo.com