Influence of Fruit Wounding on Subsequent <i>Monilinia laxa</i> Infection of Nectarines

Despite the fact that brown rot is the most economically important disease in stone fruits, the relationship between mechanical stress and infection has never been explored. Thus, to explore this connection, we carried out four experiments linking nectarine wounding and <i>M. laxa</i> infection. First, we evaluated a possible systemic reaction of the fruit to wounding that could impact the <i>M. laxa</i> infection. Afterward, we study the impact of the fruit in the environment on <i>M. laxa</i> colonies grown in vitro. Subsequently, we tested the disease susceptibility of fruits inoculated with <i>M. laxa</i> placed in the same environment as wounded fruits. Finally, in the fourth experiment, the effect of wounding on the subsequent fruit infections was evaluated at three fruit stages. As a result, we observed that there was no evidence of a fruit systemic reaction to wounding and <i>M. laxa</i> infection. In the study related to the impact of the fruit in the environment of <i>M. laxa</i>, the findings suggest that <i>M. laxa</i> “perceived” the fruit’s presence, resulting in accelerated in vitro growth. Moreover, the presence of wounded fruits in the box increased the susceptibility to brown rot. Inoculated fruits showed a delayed and reduced infection 7 h after being wounded, during the second stage of fruit development (15–19 weeks after full bloom). Moreover, a red reaction associated with inoculation was detected immediately after the fruits were wounded. Nine phenolic compounds exclusively related to the red areas were extracted, while six other compounds were present in higher proportions. These compounds may be actively involved in plant–pathogen interactions and the activation of metabolic pathways involved in nectarine susceptibility/resistance to <i>M. laxa</i>.