Integrated Management of Soybean (Glycine × max L. Merr.) by Essential Oil of Citrus × sinensis L cv.‘ Osbeck’ Epicarp in Postharvest

The essential oil extracted from the epicarp of Citrus sinensis exhibited absolute fungitoxicity against soybean‘s fungus as Alternaria alternate, Aspergillus niger, Cercospora kikuchii, Chaetomium spp., Cladosporium cladosporioides, Curvularia lunata, Fusarium roseum, Macrophomina phaseolina, Penicillium italicum, Phomopsis spp. Rhizoctonia solani, and Sclerotium rolfsii. It is very difficult to manage these pathogens by their nature of survival in seed. GC-MS studies of the oil revealed the presence of 10 chemical constituents of them limonene was found to be the major component (84.2 %). The activity of the oil was tested by the poisoned food technique and volatile activity assay. It was found that volatile activity was more toxic than poisoned food technique. The oil was extremely toxic for spore germination and it was found that at 700 ppm spore germination was inhibited in the ten test fungi out of the twelve tested. The essential oil demonstrated wide spectrum fungitoxicty. The seed were treated with essential oil for different concentration. It is evident that the treatment of essential oil inhibited the growth of dominant fungi. In 600 ppm Fusarium roseum, Penicilluim italicum, Rhizocotonia solani and Sclerotium rolfsii were inhibited but in 700 ppm all tested fungi who is found in untreated seed were inhibited. The scanning electron microscopy (SEM) was done to study the mode of action of oil in case of Aspergillus niger and it was observed that the treatment of oil leads to the distortion and thinning of hyphal wall and the reduction in hyphal diameter and absence of conidiophores.