Spatial variability of soil salinity and grapevine dieback in Chardonnay and Shiraz

Abstract

Stress due to biotic or abiotic factors often plays a crucial role in the manifestation of disease symptoms. An endophytic pathogen in healthy tissue can induce symptoms of the disease only when its host is physiologically weakened by stress. Soil salinity is a major factor limiting vineyard performance and it could also be a contributing factor in the dieback of grapevines. A survey of soil salinity and grapevine dieback was conducted in a vineyard planted with non-grafted Chardonnay and Shiraz in the Hunter Valley, New South Wales, Australia. We hypothesized that spatial soil variability might influence vine health and predispose them to trunk disease pathogens. The objectives were to assess the spatial variability of the soil, as well as vine health and grapevine dieback based on spatial correlations. Individual vines were scored according to the extent of dieback in the trunk and arms. A range of fungi were isolated from vines showing dieback symptoms. Of the 119 wood samples collected, the genera isolated were 'Botryosphaeria', 'Epicoccum', 'Pestalotia, Alternaria', 'Greeneria', 'Phaeomoniella', 'Phaeoacremonium', 'Aureobasidium', 'Phellinus' and 'Phomopsis'. The dominant genera isolated were 'Alternaria' (43%), 'Epicoccum' (41%), 'Botryosphaeria' (36%) and 'Phaeoacremonium' (14%) with others being isolated infrequently (1–10%). Soil electrical conductivity (EC) was assessed using EM38. Lateral variability of soil salinity in the vineyard was mapped using an EM38 electromagnetic sensor. Grapevine dieback was not strongly associated with soil salinity levels.