Impact of leaf spotting diseases complex on grain yield and yield components in a durum wheat population


Berraies, S., Ruan, Y., Knox, R.E., Cuthbert, R., and Campbell, H. 2019. Estimating the effect of leaf spot disease complex on grain yield, test weight and thousand kernel weight in a durum wheat population. International Symposium on Cereal Leaf Blights. Dublin, Ireland, May 22-24, 2019.


Leaf spot disease complex (LSDC) (tan spot, septoria leaf blotch, and spot blotch) is one of the most prevalent and widespread diseases affecting durum wheat production in Western Canada. Leaf spot diseases reduce the photosynthetic area of leaves resulting in reduced grain filling and lower yields particularly when the penultimate and flag leaves are infected. This study was conducted to estimate the losses caused by LSDC on grain yield, test weight, and thousand kernel weight in an adapted durum wheat population. Over four years, in a field near Swift Current, SK, we grew 167 doubled haploid durum wheat lines derived from a cross of commercial cultivars Strongfield and Pelissier. We evaluated them for natural LSDC infection using the 0-11 McFadden scale for the vertical progression of disease in the canopy. At maturity, plots were harvested and grain yield was measured. Kernel weight was determined on a sample of 1000 kernels randomly taken from the harvested grain. Test weight was determined gravimetrically on clean grain samples. Correlations and regression between LSDC reaction and grain yield, thousand kernel weight, and test weight were calculated. A significant negative correlation was observed between LSDC reaction and grain yield (r = - 0.4, P < 0.0001, n = 167). Regression analysis showed that the average yield reduction was 108 Kg ha-1 for every increment of the disease in the canopy on the 0-11 scale. On average, yield losses reached 33.7% when the flag leaf is infected. Regression analysis on the lines with disease reaction higher than seven showed yield losses of 36.9%. LSDC showed a negative relationship with test weight and thousand kernel weight, but was not significant. The results demonstrate that greater susceptibility to LSDC is related to increased grain yield losses in durum grown in southwestern Saskatchewan.

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