Post-Harvest Fungi of Stored Common Bean Cultivars in Menoua Division, West Region, Cameroon
Teh, Exodus Akwa
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In Cameroon, common bean (Phaseolus vulgaris L.) is amongst the legumes which are greatly consumed. Farmers in Cameroon especially the Menoua Division grow different common bean cultivars which after harvest, are stored to be used as food over the storage period or for sale. Storage of agricultural products become prone to fungal infection over time. Studies on the microbiology of stored common bean has identified fungi as a major contaminant. However it is possible that the incidence and severity of fungal infection vary with different common bean cultivars over the storage period. This research aimed at assessing the population of fungi on common bean cultivars both at harvest and storage grown in the Menoua Division of Cameroon and also to characterize the fungal species obtained from these cultivars. Six different common bean cultivars both at harvest and storage were evaluated for fungal contaminants using PDA media. Initial characterization of fungal isolate was done morphologically. A One-way ANOVA was performed on the fungal population on the different common bean cultivars to determine whether their mean values were significantly different (P ≤0.05). Results showed that a total of 31 fungal colonies resulted from the plated common bean cultivars at harvest, while 80 fungal colonies were obtained from the stored cultivars. Analysis of variance showed no significant difference (P ˃ 0.05) between the populations of common bean cultivars containing fungi at harvest. The population of fungi on stored cultivars differed significantly from each other (p ≤ 0.05). Highest fungal levels was observed on stored common bean cultivars. Four storage fungi genera were isolated from the different plated bean cultivars. Three could be identified as the genera Aspergillus, Fusarium, and Penicillium due to their morphological and microscopic characteristics. The fourth couldn’t be identified and was named Morphospecie or ‘Mycelia sterilia’. There was also a significant difference (P ˂ 0.0001) between the mean population of each of the fungal type isolated from the stored bean cultivars. Molecular analysis detected by the sequencing of their ITS region confirmed the presence of different fungal species. The Morphospecie was identified as Xylaria hypoxylon a member of the Ascomycetes. Other species identified included; Fusarium oxysporium, Aspergillus flavus and Penicillium aethiopicum. Phylogenetic analysis and multiple sequence alignment using mutalin revealed the relationship among the species. The species of fungi recovered from the stored cultivars signified poor preservation methods carried out after harvest. From the study it was established that Aspergillus flavus, Penicillium aethiopicum, Fusarium oxysporium and Xylaria hypoxylon were responsible for the spoilage of the common bean grains in store. There also exist differences among common bean cultivars in susceptibility to damage by fungi under storage environment by farmers in this region. The most susceptible common bean cultivar to fungal infection was the large seeded bean cultivar and the least were pinto bean, navy bean and Pea bean cultivar. It is therefore recommended that Pinto, Navy and Pea bean cultivar should be used for long term storage while the Large seeded, Black and kidney bean be used for short term storage duration by farmers.