Changes of antioxidant enzymes in ‘Thomson-Navel’ orange during induction of resistance to green mold (Penicillium digitatum (Pers.) Sacc.) as provoked by jasmonic acid, epibrassinolide, chitosan and cinnamon essential oil

Abstract

Pathogenic agents are one of the causes of post-harvest citrus fruit loss. Therefore, the aim of this study was to evaluate the effect of post-harvest treatments with jasmonic acid (ja), epibrassinolide (epiBL), chitosan (chi) and cinnamon essential oil (cin) on induction of resistance to the citrus green mold (Penicillium digitatum (Pers.) Sacc.) and reduction of fungal growth by improving the activity of some antioxidant enzymes in ‘Thomson-Navel’orange. For this purpose, a factorial experiment was conducted in a completely randomized design. Treatments included positive and negative control, jasmonic acid (5, 10, 20 and 40 μl l-1), epibrassinolide (1, 4, 7 and 10 μmol l-1), chitosan (2.5, 5, 7.5 and 10 g l-1) and cinnamon essential oil (250, 500, 750 and 1000 ppm). Characteristics such as lesion diameter and activities of antioxidant enzymes including SOD, APX, CAT and POD were evaluated for a period of 96 hours with 24 hour intervals. The results indicated that all treatments significantly decreased the lesion diameter of fruits. Consequently, chitosan treatments (7.5 and 10 g l-1) and cinnamon essential oil (750 and 1000 ppm) inhibited the spread of fungal infection better than other treatments, and therefore reduced the growth of green mold. Also, different concentrations of (ja) and (chi) increased the activity of SOD and APX enzymes, while different concentrations of (epiBR) and (cin) stimulated the activity of POD and CAT enzymes. Finally, the present study proposes using natural products as an appropriate alternative to fungicides in order to reduce the citrus green mold rot

Keywords

• peroxidase
• catalase
• superoxide dismutase
• ascorbate peroxidase
• citrus green mold
• inoculation