Management of Postharvest Diseases of Washington Navel Orange Using Combined Treatments between Essential oils and Chitosan

Abstract

Citrus infected by Penicillium ssp. and Geotrichum ssp. caused different symptoms on fruits in the field, packinghouse, or during handling causing postharvest diseases. Penicillium digitatum Sacc. and Penicillium italicum Wehmer caused green and blue moulds, respectively, however, Geotrichum citriaurantii Link ex Persn, caused sour rot. Controlling of postharvest diseases using essential oils and/or chitosan on Washington naval orange fruits during storage period were investigated. Effect of Thyme, Nerol and chitosan against the mycelial growth and spore germination of Penicillium digitatum; P. italicum and Geotrichum citri-aurantii in vitro were tried. Results showed that complete suppression of mycelial growth and spore germination of all tried fungi was achieved with Thyme and Nerol at 1.5 %. In addition to chitosan at 8.0 g/L. Thyme or Nerol at concentration of 1.5 % and chitosan at 8.0 g/ L were applied alone or in combination to study their protective effect against green, blue molds and sour rot diseases of Washington navel orange fruits. Results showed that the highest inhibition was obtained with Thyme or Nerol at 1.5 % followed by chitosan at 8.0g / L which inhibited disease incidence and severity more than 88.0 and 92.0 % respectively for green, blue molds and sour rot diseases. Single
treatments showed satisfactory impact. All tested treatments had no negative effect on fruit quality. The most effective treatments are combined between Thyme or Nerol at 1.5 % followed by chitosan at 8.0g / L which reduced the fruit weight loss and fruit disorders percentage as compared with untreated fruits. Meanwhile, no significant effect on total soluble solids percentage (TSS) was observed.