Acibenzolar-S-methyl against Botrytis mold on table grapes in vitro and in vivo

Abstract

The objective of this work was to investigate the effect of the resistance inducer Acibenzolar-S-methyl (ASM), against Botrytis mold on table grapes in vitro and in vivo. To assess the effect of ASM on mycelial growth Botrytis cinerea, different concentrations (0.125, 0.25, 0.5, 1.0, 2.0 and 3% w:v) were tested. Treatments were set up in triplicate, in a completely randomized experimental design, and replicated twice. Results were expressed in minimum inhibitory concentrations and effective dose per 50% response of mycelial growth. Healthy table grapes (cvs. Italia and Benitaka) were harvested at full ripe to evaluate the ASM 1% effect against gray mold under artificial conditions. Bunches were split into two groups in order to perform two types of experiments (spray or immersion). For both trials, treated bunches were arranged in carton boxes and stored at 2±1 °C, for one month, followed by one week of shelf-life at 22±2 °C. In order to evaluate the ASM effect against gray mold under field conditions, ASM 1% was sprayed on both cultivars one week before harvest. Grapes treated with iprodione 0.2% with three applications during the season were included as a standard chemical control. Bunches were harvested at full ripe, arranged in carton boxes and submitted to a cold storage process as described previously. Results for the in vitro experiments showed that the minimum inhibitory concentration of ASM was achieved by 3% and the ED50 was 0.04%. Under artificial conditions, for both cultivars, the efficacy of ASM was higher when the grapes were immersed than sprayed. A significant difference was observed for ASM as compared with control. Regarding the effect of ASM against gray mold in the field, the incidence of gray mold was recorded for both cultivars. For ‘Italia’ and ‘Benitaka’ grapes, ASM, iprodione and sulfur dioxide pad reduced the incidence of gray mold by 85, 79 and 77%, and by 80.5, 73 and 82%, respectively. As for the physico-chemical berry properties, none of the treatments were significantly different from the control for total soluble solids, titratable acidity and color index. A single ASM treatment applied one week before harvest is effective for controlling gray mold in ‘Italia’ and ‘Benitaka’ table grapes.