Pedicel lenticel diversity of cultivars and their influence on cell death and berry shrivel

Abstract

Shrinking berries are the common symptoms of Berry Shrivel (BS) and Late-Season-Dehydration (LSD) in grapevine cultivars. The causal events leading to the induction of both ripening disorders are still unclear, although our knowledge increased substantially in the last years. In Shiraz, berries showing shrinkage symptoms, have been associated to a mesocarp cell death, especially near the seeds. Vitality staining of BS affected berries also showed enhanced cell death near the brush region. In general, mesocarp cell death is a natural process during grape berry ripening, but a wrong timing or an enhanced intensity could result in a loss of cell compartmentation followed by an increased quantity of dead tissue. One factor inducing cell death could be hypoxia, a lack of oxygen. One hypothesis state that oxygen is supplied to berries by lenticels on their skin and on pedicels, as berry transpiration is limited after ripening start. In our study, we hypothesize that lenticels ensure the oxygen transfer to berries and that BS affected berries show an enhanced cell death near the brush region due to a lack of oxygen. Specifically, we addressed the following questions a) is there a diversity of lenticel coverage on pedicels between cultivars, b) which categories of lenticels can be observed, and c) could the number of lenticels and their structure be related to cell death and BS. Microscopic methods were used to study these questions. Our results confirmed that lenticels develop over time and cultivars diver in numbers and lenticel areas. Vitality staining of berries showed minor differences between cultivars and currently we are analyzing the structure of lenticels. With this study we hope to provide an additional piece of information to decide on the contribution of cell death to the induction of BS.