Differential response to combined prochloraz and thyme oil drench treatment in avocados against the control of anthracnose and stem-end rot

Abstract

The ability to meet consumers demand for high-quality standard fruit entails the distribution of unblemished safe fruit free of chemical residues on its edible portion. Therefore, this study was focused on investigating the influence of the combined effect of aqueous plant volatiles with half strength prochloraz solution to control anthracnose and stem-end rot in the green-skinned avocado cultivar (Fuerte). This method was applied due to its practicability on bulk fruits in packhouses and the fruits were subjected to stand-alone and combined treatments to assess the development of the disease after cold storage and observe the elicitation of the residual effect of the treatments on the defence related enzymes in ‘Fuerte’. The incidence of stem-end rot was 10% by the combination of prochloraz® (500 μg mL−1; P50) with 0.1% v/v thyme oil compared to the 58.8% incidence exhibited by the untreated fruit during storage at 6.5 °C for 14 days followed by 3 days at retail shelf conditions (15 °C) (preventative application). Citral (0.1% v/v), P50 (500 μg mL−1) + 0.1% v/v citral and yucca extract alone reduced the stem-end rot incidence to about 25% during storage. More so, thyme oil (0.1% v/v) reduced both anthracnose and stem-end rot incidence to 35% after postharvest storage and P50 (500 μg mL−1) + 0.1% v/v thyme oil and 0.1% v/v thyme oil effectively induced the activity of phenylalanine ammonia lyase, chitinase and β-1, 3 glucanase in fruit inoculated with Lasiodiplodia theobromae and Colletotrichum gloeosporioides through the improvement of quality and firmness of the fruit after storage.