PHYTOTOXICITY POTENTIAL OF PLANT EXTRACTS AGAINST ASPERGILLUS SPECIES AND AFLATOXIN CONTAMINATION IN SORGHUM (SORGHUM BICOLOR) GRAIN IN EAST HARARGHE, ETHIOPIA

Abstract

Sorghum is the most important food crop in the world and in sub-Saharan African countries including Ethiopia. However, it is prone to fungal species contamination mainly Aspergillus spp. producing aflatoxins. This study was conducted to determine the incidence of Aspergillus spp. associated with sorghum grains in the farmers fields and storages, assess in vitro antifungal activities of plant extracts against Aspergillus spp. and fumigation potential of plant extracts against aflatoxin contamination under storage conditions. A total of 90 sorghum grain samples were collected from small scale farmers’fields at harvest and 5 to 6 months later from storages during the 2018/2019 harvest from 3 districts (Babile, Fedis and Kersa) of east Hararghe, Ethiopia. Twenty plant spp. were collected from east Hararghe and tested for their antifungal ef icacy using food poisoning and paper disc dif usion techniques against A. flavus. Percent frequency of aspergillus spp. and other associated fungi were determined. Aflatoxin analysis was caried out using enzyme linked immunosorbent assay (ELISA) kit. Results showed that a total of 35 spp. of fungi belonging to 17 genera were identified on PDA. Cladosporium spp. (39.9%), Alternaria spp. (39.3), and Fusarium spp. (33.8) were most dominantly recovered from field samples, while Aspergillus spp. (97.79%) and Penicillium spp. (31.1) were frequently occurred in storage grains. Among Aspergillus spp. Aspergillus flavus was the most dominantly (41.8%) recovered fungi in stored sorghum grains. In current study, 74.5% of sorghum grain samples were contaminated with aflatoxin AFB1 (ranged from < LOD to 43.8 µg kg –1) which was directly related with frequency of toxigenic strains of A. flavus. Among the 20-plant spp. tested, most of chloroform and metanolic extracts showed statistically significant (P < 0.05) dif erence in inhibitory ef ects on mycelial radial growth, spore germination and conidial diameter of A. flavus. Crude chloroform extracts of T. vulgaris, R. chalepensis, O. sanctum, and R. officinalis showed the highest activity with 35.3, 31.6, 29.7, and 24.5 mm clear inhibition zone after 3 days of incubation, respectively. Similarly, CME of T. vulgaris, O. sanctum, R. officinalis, R. chalepensis, and M. oleifera had potent ef icacy with a clear inhibition zone of 32.5, 27, 26.2, 23.2, 22.5 mm, respectively. Only CCE and CME of T. vulgaris completely inhibited spore germination of A. flavus though most of the extracts were able to significantly reduce spore germination (%) and conidial diameter of the test fungus over the control. The CCE of R. chalepensis and CME of O. sanctum remarkablely lowered level of phytotoxicity with superiority in SGI and SVI than the other extracts. The application of CCE of T. vulgaris, O. sanctum, and R. officinalis was highly reduced the level of aflatoxin B1 to 2.23 µg kg −1 , 3.5 µg kg −1 , 4.18 µg kg −1 , respectively (at 20 mg mL −1 extract’s concentration) over the control (22.83 µg kg −1) and the EU maximum level of detection (5 µg kg −1). Therefore, exploitation of antifungal and antimycotic potential of plant extracts with proper storage handling would minimize aflatoxin contamination without a pronounced ef ect on the stored sorghum grains quality. Moreover, extensive studies on chemical profiling, extract formulation, and in vivo trails and integration are justified towards the application of extracts as part of IDM to establish ef ective management strategies