Influence of Potassium Deficiency and Temporary

Executive Summary The aim of the proposed research was to study several sites with a history of potassium deficiency using a rapid screening procedure for putrescine levels that we developed in previous work on this project. The objective was to validate our screening procedure and provide recommendations regarding sampling time so that putrescine screening can be used routinely for managing potassium deficient vineyards. During the 1992 season we analyzed leaf samples for putrescine by HPLC and a recently developed TLC screening procedure that increased sample throughput by an order of magnitude. Results show that our screening procedure can certainly be used for Cabernet sauvignon and Chardonnay and can probably be used with other varieties. The screening procedure can be used to detect elevated putrescine in leaves at bloom whether or not leaf symptoms are present. The screening procedure is equally useful at veraison and after harvest. In all cases when samples were scored by TLC as having increased putrescine, the result was confirmed by HPLC. False positives and false negatives were not observed. Putrescine in leaves as estimated by the screening procedure correlated well with a subjective evaluation of the degree of potassium deficiency suffered by the vine. Results obtained during the 92/93 season served to validate of our screening procedure. We can now provide specific recommendations regarding sampling time so that putrescine screening can be effectively used for managing potassium deficient sites. In addition we have identified several “ideal” locations to apply the procedures we have developed. Interestingly, we found one site in our study that did not fit the typical potassium deficiency syndrome. This site provides an opportunity to characterize other disorders besides potassium deficiency that can lead to increased putrescine levels in the leaves.