Bioefficacy of Piper extracts in the management of chilli anthracnose

Abstract

Chilli anthracnose, caused by a complex of Colletotrichum species, is a major disease of chilli worldwide. The objective of this research was to evaluate the efficacy of crude extracts obtained from plants in the genus Piper (Piperaceae) in a reduction of chilli anthracnose severity under controlled conditions. Inhibitory effects of the extracts were preliminary screened against Colletotrichum capsici and C. gloeosporioides on the agar medium using the disc diffusion technique. The crude extracts were obtained from either leaves or stems of 25 species of Piper, and each part of the plant was extracted with ethyl acetate and ethanol. From a total of 91 samples screened, the mycelial growth of C. capsici and C. gloeosporioides was suppressed by 12 and 13 crude extracts, respectively. The effective extracts were further studied at varying concentrations for their ability to decrease anthracnose severity. The experiments were conducted on detached red fruits and attached leaves, and each Piper extract was applied 24 h before inoculation with the pathogen. The effective concentrations of most extracts used in the fruit treatment varied from 40 to 100 mg/mL, while the concentration of all extracts in the leaf treatment was 10 mg/mL. Among nine species of Piper evaluated in vivo, P. betle, P. retrofractum, and P. griffithii showed the maximum reduction of disease severity to pathogen infestation. Scanning electron microscope (SEM) observations on the effect of the P. griffithii crude extract on C. gloeosporioides revealed significant effect on the morphological characteristics of conidia, resulting in the failure of germination and pathogen growth.