Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 6/1/2005
Citation: Smilanick, J.L., Mlikota, F.G. 2005. Predicting the field resistance to powdery mildew of grapevine selections based on the laboratory testing of young vines. American Phytopathological Society Annual Meeting. 95:S71.
Technical Abstract: The purpose of this work is to improve the speed and accuracy of the identification of powdery mildew (caused by Uncinula necator ) resistance in grapevine for breeding purposes. Fifty-seven selections were evaluated. Tests were done to determine the accuracy of laboratory leaf disk inoculation method, which used leaves from up to one year-old vines produced in the greenhouse, to predict and correlate with the vineyard resistance of young (2 to 4 years in age) or mature (10 years or more in age) grapevines. The leaf disk method employed a spore settling vacuum tower to uniformly inoculate leaf disks in the laboratory, while vineyard evaluation employed natural inoculum from susceptible vines in the vineyard. Pearson’s correlation coefficient between incidence and severity of the laboratory leaf disk inoculation method and the vineyard evaluation of mature vines was 0.999, indicating a strong correlation. The leaf disk assay quickly and efficiently identified selections that are promising for breeding mildew resistant grapevines, and confidently eliminated susceptible ones. Mildew incidence among young vines in the vineyard was very low and did not correlate with that of leaf disks. Selection of mildew resistance based on the susceptibility of young vines in the vineyard environment could result in the erroneous selection of vines that are actually mildew susceptible.