Inner necrosis in grapevine rootstock mother plants in the Cognac area (Charentes, France)

The incidence and quantification of decline-associated inner necrosis in grapevine rootstock mother plants have rarely been studied. In an experimental vineyard planted in 1991 at Saintes (Charentes), susceptibility to esca was evaluated in eleven common rootstock varieties. Fifty vines per rootstock variety were used as mother plants producing long canes which were severely pruned every year. No foliar symptoms, typical of grapevine wood diseases, were seen in field inspections conducted in the summer of 1996, 2002, 2003 and 2006. In 2007, nine trunks per variety were randomly selected and were cross-sectioned at the point of greatest diameter. All sections revealed typical esca necrosis, central and/or sector-shaped, indicating that such necrosis is very common. Every section was photographed and the percentage of necrotic area was calculated by either visual assessment or image-analysis. No significant difference was detected between these two calculating methods. Based on the mean percent necrotic area, rootstock varieties were ranked in order of susceptibility from the least susceptible, ‘1103 Paulsen’ (33%), to the most susceptible, ‘101-14 MGT’ (71%). The percent of necrotic area was correlated significantly with i) the incidence of mortality and ii) the percentage of vine sections showing white rot, a type of necrosis indicating an advanced stage of wood deterioration. This study confirmed that necrosis in grapevine wood is not always associated with foliar symptoms, but that it is related positively with grapevine mortality. Furthermore, wood necrosis in mother-plants poses a risk of disseminating associated fungi through propagation material

Grapevine roots: the dark side

Since the second half of the XIXth century, grapevine has been grown grafted worldwide to cope with Phylloxera. Consequently, the cultivated grapevine is a chimeric plant made from two genotypes which interact together. The result of this interaction must ensure a balanced functioning dedicated to fruit production in terms of quantity and quality. The rootstock acts as an interface between the edaphic environment and the scion, and is an important component of adaptation to environment. The rootstock is responsible for the uptake of water and minerals from the soil, feeding the aerial parts in exchange for a supply of carbon that is stored as reserves, or used to produce nutrients and growth regulators. Many signaling and regulating molecules, such as hormones and nucleic acids, are also exchanged between the two partners. Despite its importance, little is known about the root system and the grafting zone (rootstock-scion interface) in grapevine. Until recently the study of rootstocks received little attention from growers and the scientific community. New challenges, such as climate change, environmental issues, and yield limitations, have brought new light on the “dark side” of the grapevine. This paper reviews the main physiological processes involved in the functioning of roots and the graft interface. Key, challenging scientific issues as well as applied perspectives for the industry will be discussed

Why climate change will not dramatically decrease viticultural suitability in main wine-producing areas by 2050

The paper is a Letter arguing about a paper of Hannah et al. (1) who recently published a comprehensive study showing substantial impacts of climate change on viticultural suitability, leading to potential ecological issues. That expansion of viticulture into new areas can lead indeed to a decrease in biodiversity and an increase in water use for irrigation might lead to major freshwater conservation impacts. However, the alarming statement that suitability for winegrowing of main wine-producing areas worldwide will dramatically decrease over the next 40 y. is wrong. There is a major methodological flaws in ref. 1, mostly linked to (i) the misuse of bibliographical data to compute suitability index, (ii) underestimation of adaptations of viticulture to warmer conditions, and (iii) the inadequacy of the monthly time step in the suitability approach