Characterisation of Colletotrichum species associated with anthracnose disease in red chilli pepper (Capsicum annuum L.) in the South of Vietnam and the effectiveness of the consortium Bacillus amyloliquefaciens and Pseudomonas fluorescens

Anthracnose is one of the most destructive diseases that limits pepper production and quality worldwide. In this study, the causal agent of anthracnose in red chilli pepper in Southern Vietnam was collected and identified based on morphological characteristics and multilocus sequence regions (ITS, β-tubulin, GPDH, ACT). The antifungal activity of Bacillus amyloliquefaciens and Pseudomonas fluorescens was evaluated in vitro and in vivo under greenhouse conditions. The results revealed that the morphological analysis categorised the Colletotrichum isolates into three species: C. acutatum, C. gloeosporioides, and C. scovillei. Sequence analysis of the four genes confirmed that C. scovillei was the causal agent of anthracnose in chilli pepper in Southern Vietnam. B. amyloliquefaciens and P. fluorescens bacteria demonstrated antifungal activity against C. scovillei in vitro, with mycelial growth inhibition rates ranging from 20.79% to 78.69%. The consortium of B. amyloliquefaciens CC-LD2.4, P. fluorescens CC-FN1.1, and P. fluorescens O-BT1.2 achieved 84.4% control efficacy at 7 days after inoculation (DAI), which declined to 68.5% at 14 DAI and 41.7% at 21 DAI, at the flowering stage, and achieved 100% control efficacy at the fruiting stage. B. amyloliquefaciens CC-LD2.4 showed very high chitinase, protease, and cellulase activities (halo diameter of 26.7 mm, 22.7 mm, 21.5 mm), whereas P. fluorescens CC-FN1.1 was very high in protease and cellulase (14.3 mm, 12.4 mm) but weak in chitinase (5.1 mm), and P. fluorescens O-BT1.2 exhibited overall lower activities (3.4-9.9 mm). There is still considerable room to optimise bacterial consortia to develop bio-fungicides that meet the requirements for an alternative or advanced solution for controlling anthracnose in red chilli peppers in sustainable agriculture.