Occurrence of Pythium Rot of Chinese Cabbage in Egypt and its Biocontrol Measures

Abstract

In Egypt, Chinese cabbage Brassica rapa var. pekinensis is a recently introduced as a winter crop grown throughout the country along the Nile valley as well as in new reclaimed lands. Pythium rot of Chinese cabbage was detected during the cultivation season 200⁵⁄₂₀₀₆ at four governorates throughout the north side of Egypt. Isolation trails revealed that Pythium ultimum was the causal organism of disease incidence. The cultivar of Chinese cabbage Napa (green) showed higher susceptibility to infection than Michihli cv. (red). Trichoderma harzianum, T. viride, Bacillus subtilis and Pseudomonas fluorescens isolated from the rhizosphere of healthy Chinese cabbage could inhibit the in vitro growth of P. ultimum at different degrees. Under greenhouse and field trails, applying of biocontrol agents as a combination of soil mixing plus root dipping method was generally more effective than each method applied individually for suppressing Pythium rot incidence followed by soil mixing and root dipping methods. The applied bioagents could be arranged according to their activity for suppressing the disease incidence as follows: T. harzainum, B. subtilis, T. viride and P. fluorescens, respec- tively. The use of biocontrol agents as soil mixing and root dipping treatments could provide additional protection against crop loss due to Pythium rot disease.