In vitro evaluation of plant essential oils against Alternaria alternata causing fruit rot of grapes

Alternariafruitrot(AFR)causedbyAlternariaalternataisaseriousthreattogrape marketvaluesinPakistanduringpost-harveststages,atthetimeofhandling,storage transportation and distribution respectively. The objective of this study is to determine the anti-fungal activities of plant essential oils against Alternaria alternatacausingfruitrotofgrapes.Forthispurpose,threeselectedplantessential oils(EOs)viz.Kikar(Acacia karoo),Moringa(Moringa oleifera)andSukhchain(Pongamia pinnata) essential oilsat200,400and600 ppm concentrations were investigated by using different methods under in vitro conditionagainstpreviouslyisolatedcultureofA.alternatadesignatedas(Isolate ID.AA4PL1)ongrapebunches.ResultsshowedthatPlantEOofSukhchainat allconcentrationsshowedsignificantresulttoinhibitthemycelialgrowth(89.4,92 and 96.2 percent) in contact assay method as well as 96.2, 97 and 98.2 % growth inhibitionregardingfungalculturetransfer(FCT)experimentwhile,incaseofwell diffusionmethod32%,41%and48%growthinhibitionwasrecordedat7thdayof incubationfollowedbyMoringaEOandKikarEOascomparedtocontrolthat showed 0% growth inhibition was measured. Moreover, results related to spore germination assay revealed that Sukh chain essential oil at 200, 400 and 600 ppm showed significantinhibition ofgermtubelengthofA.alternata(140.8μm,77.5μmand34.1 μm) as compared to control in which germ tube length was recorded 250 μm respectively. It was concluded that Sukhchain EO has a great potentialto inhibit the growth of A. alternata and can be further used as a strong antifungal agent against this pathogen under in vivocondition.