Utilization of chitinolytic bacterial isolates to control anthracnose of cocoa leaf caused by Colletotrichum gloeosporioides

Abstract

Colletotrichum spp. are causal agents of anthracnose in many plant species. Biological control of Colletotrichum spp. utilizing bacterial isolates and fungi has been reported. However, chitinolytic bacterial isolate utilization to control anthracnose of cocoa leaf has not seemingly been studied yet. In this study, we used chitinolytic bacterial isolates to reduce anthracnose severity and incidence caused by Colletotrichum gloeosporioides. Identification of the chitinolytic isolates was conducted for their morphological and biochemical traits, and the sequencing of 16S rRNA was to know their related species. Assay of antagonistic bacterial chitinolytic to C. gloeosporioides was conducted in minimum salt medium agar with 2% colloidal chitin as sole carbon source. To examine ability of the chitinolytic isolates in reducing anthracnose severity and incidence, cocoa leaves were treated with the isolates prior infestation of the conidia. Identification of 16S rRNA showed that KR05, LK08, BK13, BK15 and BK17 isolates were  Enterobacter  sp.,  Enterobacter  cloacae,  Bacillus sp.,  Enterobacter sp., and Bacillus sp., respectively. All chitinolytic isolates inhibited growth of C. gloeosporioides in vitro to some extent. Microscopic studies showed morphological abnormalities of C. gloeosporioides  hyphae that is, broken, lytic, rolled, twisted, curled and abnormal branching of hyphae as a result of antagonistic mechanism caused by the chitinolytic isolates. All chitinolytic isolates were able to reduce anthracnose severity and incidence on cocoa leaves from 0.8 to 3.2% and 4 to 12%, respectively.

Keywords: Anthracnose, biological control, chitinolytic bacteria, C. gloeosporioides, cocoa.

African Journal of Biotechnology, Vol 13(15), 1631-1637