Author(s): ElGamal NG
Late and early blight caused by Phytophthora infestans and Alternaria solani are the most serious diseases attacking potato plants. Ascorbic acid (AA), Dichloro-isonicotinic acid (INA) ethylene diamine tetra acetic acid (EDTA) and calcium chloride were evaluated against late and early blight diseases under greenhouse and field conditions. Under greenhouse conditions, the highest reduction in diseases severity was obtained by AA at 2 & 3 g/l, and INA at 50.0 and 100 mM , they reduced late and early blight severity more than 75.0 and 82.1%, followed by EDTA and Calcium chloride, respectively. On the other hand the combined treatments between AA at 2 g/l and INA at 50 or 100 mM reduced the late and early diseases severity between (86.6-90.0 %) and (90.0-93.3 %), respectively. These treatments showed an increase in activity of both ß-1,3-glucanase and chitinase as 115 and 109 %, respectively. Similar trend was observed under field conditions, the most effective inducers were combination treatments between AA at 2.0g/l and INA at 50.0 or 100 mM which reduced the late and early blight severity more than 88.7 and 86.1 % and increased tuber yield from 70.0 up to 83.3 % during the two successive winter and summer cultivation seasons. Individual treatments of AA and INA showed moderate effect on reduction in diseases severity and yield increase, although they were superior to Calcium chloride as well as fungicide Redomil-plus in this concern. It could be suggested that combined treatments between ascorbic acid and INA as applicable, safe, cost effective and fungicide alternative might be used for controlling late and early blight diseases of potato plants.