Water Relations Factors Relating to Syrah Disorder on the Central Coast
The 2005 research on Syrah Disorder on the Central Coast continued to look at the effects of environmental variables on symptom expression; in particular, water stress and salinity stress were analyzed in more detail. Work also continued to investigate a potential common virus in affected plantings.
The applied irrigation treatments and salinity treatments led to measurable differences in leaf water potential, stomatal conductance, and berry weight, but did not lead to notable differences in leaf symptoms at the two principal research sites. However, both of the experimental blocks as a whole displayed very different symptom expression in 2005 as compared to 2004; one block had very delayed and reduced symptoms as compared to 2004, while the other block had much more severe symptoms. This suggests that environmental influences on a larger scale (such as winter rainfall amounts, crop load, etc.) do play some role in symptom expression. Continued virus testing has not yet identified a common pathogen that could explain the symptoms, which in many instances resembles leafroll virus.