Salicylic acid and jasmonic acid can suppress green and blue moulds of citrus fruit and induce the activity of polyphenol oxidase and peroxidase

Abstract

The ability of salicylic acid and jasmonic acid to suppress post-harvest infection with green mould Penicillium digitatum and blue mould P. italicum on three citrus species Citrus reticulata 'Kinnow', C. limon 'Meyer Lemon', and C. limetta 'Mosambi' was evaluated in a dose-response study. Salicylic acid (SA) and jasmonic acid (JA) were applied to the fruits as a post-harvest dip treatment followed by wound inoculation with the pathogens. Both resistance inducers caused a significantly lower disease severity compared with the infected but non-treated control, whereas disease incidence was not significantly lower than in the control. The efficacy of both SA and JA in reducing disease severity was concentration-dependent; the use of higher concentrations resulted in a greater degree of suppression. All the Citrus species tested in this study showed different responses in terms of disease development. C. limon 'Meyer Lemon' showed the highest disease development, and C. limetta 'Mosambi' the lowest. To get an insight into the mechanisms underlying the increase in resistance, the activity of defence-related enzymes -peroxidase (POD) and polyphenol oxidase (PPO) -was recorded in SA-and JA-treated fruit peelings. The activity of both enzymes was directly proportional to the concentration of the SA and JA applications. The highest activity of PPO and POD was observed in C. reticulata 'Kinnow' and the lowest in C. limon 'Meyer Lemon' fruits. This study is the first to document an increase in the activity of PPO and POD in SA-and JA-treated Citrus species in the presence of blue mould and green mould pathogens.Ke y wo r d s: enzymes, Penicillium digitatum, P. italicum, post-harvest, resistance inducers Abbreviations: BM − blue mould, GM − green mould, JA − jasmonic acid, POD − peroxidase, PPO − polyphenol oxidase, RH -relative humidity, SA − salicylic acid

Temporal Patterns and Inter-Correlations among Physical and Antioxidant Attributes and Enzyme Activities of Apricot Fruit Inoculated with Monilinia laxa under Salicylic Acid and Methyl Jasmonate Treatments under Shelf-Life Conditions

“…The temporal increase in POD activities was in line with the reductions in BRI and LD ( Figure 1 A,B). This result with MeJA was in line with the studies of Yao and Tian [ 34 , 35 ] and Moosa et al [ 119 ], in which the authors demonstrated that JA induced a stronger POD activity and decreased LD caused by M. fructicola , P. expansum and P. digitatum in sweet cherry, peach and citrus fruits, respectively.…”

“…Oxidation of peroxidases results in a more rigid cell wall through the increased matrix of polysaccharide and glycoprotein molecules [ 112 , 115 ]. Thus, POD plays a key role in the reinforcement of cell walls; therefore, it can protect the cell wall against infection by fungal pathogens [ 116 , 117 , 118 , 119 ]. Our results indicated that postharvest treatments of SA and MeJA induced higher POD activities in M. laxa -inoculated apricot fruits compared with water-treated fruits ( Figure 4 ).…”

Synthesis and Antifungal Activities of Cinnamaldehyde Derivatives against Penicillium digitatum Causing Citrus Green Mold

“…In a different study, it was also noted that the incorporation of trans-cinnamaldehyde with poly(lactic acid) and poly(butylene adipate-co-terephthalate) provides better performance as an edible film [35]. Overall, results support the idea suggested by Moosa et al [36] where the biomaterials were reported as high potent against green and blue mold of citrus fruits. e MIC and MFC examinations are being applied as one of the most important indexes to access the inhibitory efficiency of antifungal chemicals.…”

Effect of the AM Fungus Sieverdingia tortuosa on Common Vetch Responses to an Anthracnose Pathogen

“…It is not the only way for plants to resist pathogens; it can be combined with other ways to resist pathogen infection (Xia et al, 2015;Wang X. Y. et al, 2019). Several plant hormones are known to mediate plant defense responses against pathogens (Verma et al, 2016), of which the increase in concentration of SA and JA helps to enhance the activities of POD and PPO (Moosa et al, 2019). The results showed that inoculation with the AM fungus increased the concentrations of JA and SA in plants infected with pathogens.…”