Effect of elevated temperature on the onset and rate of mesocarp cell death in berries of Shiraz and Chardonnay and its relationship with berry shrivel

BACKGROUND AND AIM. Berry water loss at late stages of ripening is a cultivar dependent-trait correlated with mesocarp cell death. We tested the hypothesis that elevated temperature anticipates the onset and increases the rate of mesocarp cell death. The implications of these putative effects on the time course of berry shrivel were also investigated. METHODS AND RESULTS. We assessed the progression of mesocarp cell vitality and the degree of shrivelling in berries from a factorial field experiment combining two thermal regimes (elevated temperature and control) and two cultivars (Shiraz and Chardonnay). A bilinear model was used to objectively discriminate the onset of cell death and to quantify the rates of cell death before and after the inflection point in chronological and thermal scales. Elevated temperature advanced the onset of mesocarp cell death of berries and increased the rate of cell death in the period onset-harvest for both cultivars. There was a close correlation between the proportion of living tissue and shrivel for Shiraz, but no shrivel was observed in Chardonnay despite significant mesocarp cell death. CONCLUSION. Elevated temperature accelerated both mesocarp cell death and berry shrivelling in Shiraz and accelerated mesocarp cell death but had no impact on shrivel in Chardonnay. Mesocarp cell death seems necessary but not sufficient to explain berry shrivelling. SIGNIFICANCE OF THE STUDY. Understanding the functional links between berry shrivel and mesocarp cell death and their responses to environmental drivers would likely contribute to management practices that could reduce the severity of shrivel in a context of warmer conditions.

M. Bonada, V.O. Sadras and S. Fuentes