Inception, Progression, and Compositional Consequences of a Berry Shrivel Disorder
Berry shrivel (BS) is a ripening disorder of grapes; symptoms include shriveling of berries and low soluble solids before and at harvest. BS is distinct from bunchstem necrosis (BSN) in that BS rachis tissue remains green and does not undergo necrosis. BS berries were somewhat firmer than normally developing berries until just after veraison, but then softened faster than normally developing fruit. Soluble solids increased in all berries after veraison, but Sugar accumulation on a per berry basis essentially stopped in BS berries several weeks before visible symptoms. Compared to normally developing berries, BS berries lost weight through water loss and mesocarp cell viability began to decline at about the same time as shriveling became apparent. BS berries had reduced anthocyanins in the skin, but had more skin tannin at harvest. Juice pH of BS berries was lower than that of normally developing berries, although amounts of tartrate and malate per berry were similar at harvest. Nonshriveled berries on vines that had BS symptomatic clusters had composition intermediate between BS and normally developing berries for sugar per berry, Soluble solids, pH, anthocyanins, and skin tannins, indicating that BS disorder affects the entire vine rather than individual clusters or berries. BS vines at one site had consistently less negative water potentials than normally developing vines, but that was not the case at a second site. BS and normally developing vines were tested for common viruses as well as Xylella fastidiosa bacteria, but no differences were found.