Effect of temperature and pH on Olpidium brassicae
1994
Gharbi, S. | Verhoyen, M. (Universite Catholique de Louvain, Louvain-la-Neuve (Belgium). Faculte des Sciences Agronomiques)
The development of lettuce big vein virus and lettuce ring necrosis has always been associated with low temperatures. These two agents transmitted by Olpidium brassicae may reduce by 30 per cent the yield of a lettuce culture. The influence of temperature and pH on O. brassicae has been studied to determine the optimal conditions of multiplication and survival of the fungus. Concerning the survival conditions, the optimal temperature for viability is about 5 degrees. At this temperature, the zoospores remain viable during 72 hours. The optimal temperature of the fungus multiplication in the roots is on the other hand at 20 degrees. Resting spores and zoosporanges of O. brassicae are frequently observed in the roots when the fungus is multiplied at 20 degrees. The effect of pH on O. brassicae shows that the viability of zoopores is optimal when they are suspended in a solution of pH between 6 and 8. Temperature and pH of nutrient solutions intended for lettuce in hydroponic systems are the same as those for the multiplication of the fungus; that makes fungus eradication very difficult.
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