Abstract
Drawbacks associated with the use of chemical fungicides to control plant pathogenic fungi such as Botrytis cinerea stimulate the need for alternatives. Therefore, the present study was carried out to determine the antifungal potentials of Moringa oleifera extracts against B. cinerea. Phytochemical analysis using qualitative chemical tests revealed the presence of huge amount of crucial phytochemicals compounds like phenolic compounds, alkaloids and saponins in the M. oleifera leaf extract. Antifungal bioassay of the crude extracts indicated better mycelial growth inhibition by methanol leaf extract (99%). The minimum inhibitory concentration (MIC) was 5 mg/ml with 100% spore germination inhibition and minimum fungicidal concentration (MFC) was 10 mg/ml with 98.10% mycelial growth inhibition using broth micro dilution and poisoned food techniques. Gas chromatography-mass spectrometry (GC-MS) analysis led to the identification of 67 volatile chemical compounds in the leaf extract with 6-decenoic acid (Z)- (19.87%) was the predominant compound. Further chemical elucidation of the crude extracts performed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) showed the presence of non-volatile chemical compounds, mostly flavones, flavonoids and phenolic acids (i.e. quercetin and kaempferol). Scanning electron microscopy and transmission electron microscopy analysis showed positive effect of M. oleifera leaf extract on the treated conidia and mycelium of B. cinerea. Findings revealed that irreversible surface and ultra-structural changes with severe detrimental effects on conidia and mycelium morphology compared to control treatment. Overall findings suggested that M. oleifera leaf extract is a promising candidate for biological control of fungal pathogens, thus limiting overdependence on chemical fungicides.
Highlights
Gray mold disease is caused by Botrytis cinerea Persoon: Fries [teleomorph: Botryotinia fuckeliana Whetzel] is a serious disease of tomato (Solanum lycopersicon L.) in Malaysia and in most areas of the world (Kim et al, 2016)
From our results it is evident that the analysis of the percentage yield of the crude extracts obtained from M. oleifera leaf and seeds with different solvents showed that methanol gave the highest yield (14.16%) from leaf (Table 2), followed by ethanol (10.23%) and the lowest yield was observed in distilled water (1.71%)
The highest growth inhibition was observed under both isolate BCH02 (>99.00%) and BCH07 (>99.00%) by methanol leaf extract, 99.00% in isolates BCH07 by methanol seed extracts, followed by 98.00% growth inhibition by ethanol leave and seed extracts as observed in both isolates
Summary
Gray mold disease is caused by Botrytis cinerea Persoon: Fries [teleomorph: Botryotinia fuckeliana (de Bary) Whetzel] is a serious disease of tomato (Solanum lycopersicon L.) in Malaysia and in most areas of the world (Kim et al, 2016). The broad host range of B. cinerea leads to great economic losses, during crop growth and during the storage and on transit of the harvested products (Elad, 2003). Gray mold occurs frequently in the tomato greenhouses in Cameron Highlands areas of Pahang in Malaysia resulting in reduced plant growth, premature leaves defoliation, fruit rot and adverse effect on yields. If the disease is not properly and effectively managed, it can be destructive enough to cause extensive yield losses leading to significant backwards in the tomato industries and/or tomato growers
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