ABSTRACT

Laboratory experiments were carried out to investigate the fungitoxic potentials of some plant extracts and Trichoderma harzianum in the management of post-harvest fungal deterioration of potato. The experiments were laid out in Completely Randomized Design (CRD) and replicated three times and data collected were subjected to analysis of variance (ANOVA) using Genstat discovery edition 1.Significant treatment means were seperated using Fisher’s least Significance Difference L.S.D at 5% level of probability. Pathogenicity test revealed that Aspergillus niger, Rhizopus stolonifer Aspergillus flavus, Fusarium oxysporum and Alternaria solani caused rot on potato tubers by utilizing the substrate for their growth development. A. niger was found to be more virolent having the highest rot incidence of 77.5%, followed by R. stolonifer, A .flavus and F. oxysporum with rot incidence of 66.5%, 59.7%, 53.3% respectively, whereas the A. solani depicted a lower pathogenic effect with rot incidence of 33.6%. The result of the inhibitory potentials of the extracts of A. indica, M. oleifera (stem), M. oleifera (leaves) and C. odorata against the five fungal pathogens showed significant differences (P<0.5) in  their rates of fungitoxicity on A. niger, A. flavus, R. stolonifer, F. oxysporum and A. solani. The effect of A. indica extract gave the highest means inhibitory effect of 65.4% on A. niger while the least means growth inhibition of 18.4% was recorded by C. odorata extract on R. stolonifer. The results obtained when plant extracts were applied after inoculation with spore suspension fungi isolates showed high significant effect in rot incidence and severity. C. odorata was less effective in controlling the mycelial growth and thus, had the highest percentage diseases incidence of 50.2% .The lowest incidence of rot (21.6%) was recorded with A. indica extract. R. stolonifer showed a stronger resistance to the plant extracts than A. niger, A. flavus, F. oxysporum and A. solani. Results obtained from laboratory screening of T. harzianum for antagonism towards fungal isolates of potato tuber rot, showed that mutual inhibition was observed whenT. harzianum was co-inoculated with -A. solani, A. niger, A. flavus  and F. oxysporum, while  R. stolonifer overgrew the mycelium of T. harzianum on a PDA. The results of this study have shown the fungitoxic potential of these plants materials and antagonistic effects of T. harzianum in the control of the postharvest rot of potato which could be exploited as alternative to synthetic fungicide in the control of potato rot incited by fungal rot organisms