Asian Research Thesis Index

Abstract

Fusarium oxysporum f.sp. lycopersici (Fol) cause Fusarium wilt, a devastating disease in tomato, affecting the crop yield and causes economic loss worldwide. Synthetic fungicides are widely used in controlling the wilt disease, however they have been questioned due to their environmental concern. Therefore, this study was designed to screen fungal species for their antifungal potential against this destructive disease. Initial dual culture assay of fungal species revealed Aspergillus niger, Penicillium EU0013 and Alternaria solani as inhibitory to the pathogen due to their higher inhibition (%) 51.54 ± 1.09, 63.85 ± 3.26 and 46.15 ± 2.18 % respectively. During culture condition optimization studies, Glucose peptone yeast extract broth (GPYB) was found suitable for higher antifungal activity and production of compounds from A. niger and Penicillium whereas A. solani showed higher antifungal activity in glucose nutrient broth (GNB). The three fungal species showed maximum zone of inhibition against the pathogen at 30 °C and at slightly acidic pH. Penicillium sp. showed maximum zone of inhibition (9.20 ± 0.14 mm) amongst the three fungal species against Fol, therefore this species was selected for in vivo pot experiments. It was observed that with the application of Penicillium extract, plants showed no symptoms of wilting even after 40th day of plantation. Bioassay guided investigation of the fungal species leaded to isolation of eight antifungal compounds. Among these compounds, two completely new from Penicillium sp. with m/z 255 and 223 [M+H]+ and one from A. solani with m/z 273 [M+H]+ were characterized. Three known compounds from A. niger with m/z 557, 571 and 665 [M+H]+ and two from Penicillium sp. with m/z 143 and 239 [M+H]+ and one from A. solani with m/z 273 [M+H]+ are reported for their antifungal activity against Fol the first time in this study. MIC value of the purified compounds showed that the compounds were active between 40 to 120 μg·mL-1. Identification and characterization of these antifungal compounds might provide lead structures for developing them as fungicide in future.

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