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

Abstract

Alternaria fruit rot (AFR) caused by Alternaria alternata is a serious threat to grape market values in Pakistan during post-harvest stages, at the time of handling, storage transportation and distribution respectively. The objective of this study is to determine the anti-fungal activities of plant essential oils against Alternaria alternata causing fruit rot of grapes. For this purpose, three selected plant essential oils (EOs) viz. Kikar (Acacia karoo), Moringa (Moringa oleifera) and Sukh chain (Pongamia pinnata) essential oils at 200, 400 and 600 ppm concentrations were investigated by using different methods under in vitro condition against previously isolated culture of A. alternata designated as (Isolate ID. AA4PL1) on grape bunches. Results showed that Plant EO of Sukh chain at all concentrations showed significant result to inhibit the mycelial growth (89.4, 92 and 96.2 percent) in contact assay method as well as 96.2, 97 and 98.2 % growth inhibition regarding fungal culture transfer (FCT) experiment while, in case of well diffusion method 32%, 41% and 48% growth inhibition was recorded at 7th day of incubation followed by Moringa EO and Kikar EO as compared to control that 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 significant inhibition of germ tube length of A. alternata (140.8 µm, 77.5 µm and 34.1 µm) as compared to control in which germ tube length was recorded 250 µm respectively. It was concluded that Sukh chain EO has a great potential to inhibit the growth of A. alternata and can be further used as a strong antifungal agent against this pathogen under in vivo condition.