Host-pathogen relationship of potato to late blight (Phytophthora infestans (Mont.) De Bary) as promoted by nitrogen source in calcareous soil [Egypt]
1988
El-Sheshtawi, M. (Mansoura Univ. (Egypt). Faculty of Agriculture) | Dawood, M.K. | Doss, M.
Potato plants cv. Alpha grown in calcareous soil at El-Noubaryia west were pathologically and biochemically tested for the natural infection with late blight disease caused by Phytophthora infestans after receiving various nitrogen fertilizers (ammonium sulfate, urea, ammonium nitrate and calcium nitrate). Leaf infection index and tuber infection %, production ability, total chlorophyll content, phenol level and sugars content were determined. Application of urea or ammonium sulfate decreased the disease incidence and severity. Moreover, the use of the later fertilizer increased both total tuber yield and weight of healthy and diseased plants. Biochemical studies revealed decrease in total chlorophyll and sugars content in leaves and tubers of the diseased plants, respectively. Ammonium sulfate or urea, however, did not have great effect in this respect as compared with the effect of ammonium or calcium nitrate. On the other hand, phenolics level was highly increased in diseased plants. Such increase was more pronounced in plants which received urea or ammonium sulfate. This may be explained by the low percent of disease incidence occurring in plants receiving either of these two fertilizers
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