SCREENING OF MICROBIAL BIOPESTICIDES AGAINST POST-HARVEST FUNGAL PATHOGEN COLLETOTRICHUM SPP A PRELIMINARY STUDY

Abstract

Most common fungal pathogens are found in Colletotrichum genus which cause economically significant anthracnose or blight disease in a variety of tropical and subtropical fruit and vegetables. Despite that, the excessive application of chemical pesticides in agriculture has caused many problems such as poor soil fertility, pollution and risk to human health due to the toxic accumulation of the pesticides in the soil. This study was carried out to isolate potential bacterial colonies from five different soil sources around Universiti Malaysia Terengganu and to the screen isolated bacteria for antagonistic effect against Colletotrichum species. In total, 50 bacterial strains were isolated and subjected to selective screening to distinguish bacterial strains capable of inhibiting Colletotrichum sp. Based on the selective screening, nine bacterial strains with different morphology were selected and tested further in quantitative screening by calculating their percentage of inhibition of radial growth (PIRG). The results showed that S5-H strain demonstrated the highest inhibition effect at (75.67 ±2.86)%, followed by S5-I strain (68.89 ±5.93)%, S5-D strain (66.89 ±6.15)%, S3-C strain (60.33 ±3.19)%, S5-F strain (57.89 ±4.66)%, S5-G strain (53 ±5.79)%, S2-I strain (41.33 ±7.26)%, S4-B strain (40 ±7.07)% and S3-D strain (38.33 ±8.90)%. Based on the results, bacterial isolate S5-H with yellow, round, convex and entire colony from mangrove muddy sediment was shown to have a potential to be utilized as biopesticides against Colletotrichum sp. Nevertheless, this study requires further work in the future focusing on species identification by 16S rRNA phylogeny and mechanism of action exhibited by S5-H strain.