Development of effective means with low risk to human health and environment is needed to control postharvest pathogens as fruits are vulnerable to attacks of various microorganisms upon harvest due to high moisture and nutrient content. Leaves and flowers of Plumeria alba, P. acutifolia and P. rubra were extracted with different solvents to compare the profile of phytochemicals. C. sinensis (sweet orange) was selected to determine the postharvest fungal pathogens of its fruits. Various methods were followed to isolate the fungal pathogens from oranges and investigated their control by using Plumeria species extracts. Phytochemical analysis has revealed the presence of alkaloids as the major phytoconstituent irrespective of plant species and parts used followed by flavonoids and glycosides. Terpenoids, tannins, phenols were the other major phytochemicals found in the extracts. Six fungi were isolated from sweet oranges with Penicillium digitatum as the predominant one followed by Aspergillus sp. and Rhizopus arrhizus. Antifungal assay revealed the potential fungistatic activity of petroleum ether leaf and flower extracts whereas chloroform, methanol and aqueous extracts were completely failed to control the growth of fungal isolates. Flower extracts of P. rubra had the best antifungal activity against all the isolates but with no activity of leaf extracts. However, a significant fungistatic activity was observed with both leaf and flower extracts of P. acutifolia and P. alba. The extracts exhibited significant activity against the blue green mold, P. digitatum. This study suggests the potential value of using crude flower and leaf extracts of Plumeria species to combat postharvest fungal pathogens of sweet oranges thereby extending their shelf life.
G. Sibi, Saurabh Awasthi, K. Dhananjaya, H. Mallesha and K.R. Ravikumar, 2012. Comparative Studies of Plumeria Species for their Phytochemical and Antifungal Properties Against Citrus sinensis Pathogens. International Journal of Agricultural Research, 7: 324-331.