POST HARVEST DISEASES IN SOME SELECTED ROOT AND TUBER CROPS AND IDENTIFICATION THEIR CAUSAL AGENTS

Abstract

The experiment was conducted at MS Laboratory, Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka-1207 during the period of August 2019 to March 2020 to isolate, identify, and characterize the causal agents responsible for the post-harvest spoilage of some selected root and tuber crops. Potato, sweet potato, radish and carrot were used as samples. Infected samples were collected from different markets in Dhaka city. The postharvest fungi were isolated on PDA medium following tissue planting method.

Five different

fungi genera were isolated and identified viz. Aspergillus niger, Geotrichum candidum, Rhizopus stolonifer, Fusarium spp. and Penicillium digitatum. Of these, Fusarium spp. has the highest percentage of frequency of occurrence in potato, carrot and radish. In carrot, Aspergillus niger showed more frequency of occurrence than Geotrichum candidum but in case of sweet potato, the occurrence of Rhizopus stolonifer was found to be more than Penicillium digitatum. Pathogenicity tests revealed that all the isolated fungi were pathogenic to their respective host as post-harvest pathogens. Effect of different media and temperature on growth of isolated fungi were studied. On PDA media, the highest radial mycelial growth (4.06 cm) at 8 DAI was recorded in Aspergillus niger (carrot) which was statistically similar with Rhizopus stolonifer (sweet potato) whereas, the lowest radial mycelial growth (2.54 cm) was recorded in Fusarium oxysporum (radish). The highest radial mycelial growth was observed in PDA followed by CDA media. Most of the isolated fungi showed the highest growth rate at 30℃ temperature, whereas, the growth rate of Rhizopus stolonifer was found the highest at 25℃ temperature.