Coating properties, resistance response, molecular mechanisms and anthracnose decay reduction in green skin avocado fruit ('Fuerte') coated with chitosan hydrochloride loaded with functional compounds

Chitosan hydrochloride coating loaded with vanillic acid (CH-V) (0.07 %) or caffeic acid (CH-C) (0.07 %) controlled the anthracnose decay in preventatively inoculated green skin avocado Fuerte with C. gloeosporioides and in naturally infected fruit; decay was reduced less than 10 % after cold storage at 6.5 degrees C and 85 % RH for 28 d and at 7 d market shelf conditions at 18 degrees C. CH-V or CH-C coating induced higher upregulation of PAL (phenylalanine ammonia lyase), CHS (Chalcone synthase), avfad12-3 (Delta 12 fatty acid desaturase), avfael (Fatty acid elongase) genes with a concomitant increase in skin epicatechin and lowest LOX (lipoxygenase) expression. CH-V coating showed a higher impact on mode of action than the CH-C. CH-phytochemicals coated fruit ripened with higher overall acceptance. FTIR data showed the chemical interaction of phytochemicals with CH. Complex of CH and phytochemicals, optimal adhesion agent between the pathogens and the fruit, possibly favoured the phenolic compound-fungus interaction and cell damage.

Automated summary

The study revealed that chitosan hydrochloride coating loaded with vanillic acid or caffeic acid can effectively control anthracnose decay in avocados, reduce decay occurrence to a lesser extent, and provide some protection for fruit quality. This coating may achieve these effects by inducing the expression of specific genes, increasing skin epicatechin content, and reducing LOX expression in the fruit. Additionally, the complex of chitosan and phytochemicals may help prevent fungal invasion and reduce fruit damage.