Abstract
Choanephora cucurbitarum is the causal agent of Amaranthus hybridus shoot disease, which is primarily associated with the actively growing tips of the shoot. Predominant phylloplane microbiota associated with the A. hybridus shoot under field conditions were Xanthomonas campestris, Erwinia herbicola, Bacillus subtilis, and Serratia sp. A considerable zone of inhibition developed between the pathogen C. cucurbitarum and the isolates of X. campestris, E. herbicola, and B. subtilis on potato dextrose agar (PDA) plates. No zone of inhibition developed between the pathogen and Serratia sp. Inoculation of A. hybridus plants with C. cucurbitarum and the isolated phylloplane micro-organisms showed a remarkable reduction in the subsequent incidence of disease. Sixty-seven per cent of A. hybridus plants showed disease symptoms when it was inoculated with X. campestris or E. herbicola, while 33.3% developed the shoot disease when B. subtilis was applied. This study confirmed that biological control operates in nature, a situation that can be exploited to control shoot disease of A. hybridus caused by C. cucurbitarum.
