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ARS Home » Northeast Area » Geneva, New York » Grape Genetics Research Unit (GGRU) » Research » Publications at this Location » Publication #313877
Title: Effect of detergent on the quantification of grapevine downy mildew Sporangia from leaf discs

Author
item KONO, ATSUSHI - National Agricultural Research Organization - Japan (NARO)
item SATO, AKIHIKO - National Agricultural Research Organization - Japan (NARO)
item REISCH, BRUCE - Cornell University
item Cadle-Davidson, Lance

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2015
Publication Date: 5/15/2015
Citation: Kono, A., Sato, A., Reisch, B., Cadle Davidson, L.E. 2015. Effect of detergent on the quantification of grapevine downy mildew Sporangia from leaf discs. HortScience. 50(5):656-660.

Interpretive Summary: Grapevine downy mildew (DM) is a major disease, especially in humid viticultural areas. Development of resistant cultivars is an important objective for grapevine breeding. However, reproducible and inexpensive methods are needed to identify grapevines with DM resistance. To this end, researchers demonstrated that a very dilute detergent was effective 1) to prevent DM from sticking to plasticware and 2) to improve the accuracy of quantification. We developed a DM quantification method that was almost perfectly correlated with counting DM spores. Using three breeding populations, researchers demonstrated the method worked well. In the end, the method we developed is high-throughput, inexpensive, and accurate for quantifying DM.

Technical Abstract: Grapevine downy mildew (DM), caused by the oomycete Plasmopara viticola (Berk. & Curt.) Berlese & de Toni, is a major disease, especially in humid viticultural areas. Development of resistant cultivars is an important objective for grapevine breeding. In order to establish a reliable and inexpensive quantitative method to aid in breeding for DM resistance, we improved the method for counting the number of sporangia on leaf discs, and developed a method for counting the number of sporangia in solution. In order to prevent the loss of DM sporangia from adhesion onto plastic ware, we found as little as 0.01% Tween 20 was effective. On the other hand, this detergent was shown to have a severe inhibitory effect upon DM infection of leaves. We developed a sporangia counting method using dried droplets of DM suspensions, and the method was highly correlated with counting by hemacytometer (R2 > 0.96). The non-parametric Spearman’s rank correlation between visual rating and the number of the sporangia are as high as ' = 0.82 to 0.91, suggesting that evaluation by the visual rating could provide a good estimation of the sporangia numbers on leaf discs. We established a high-throughput and inexpensive method with acceptable accuracy for DM resistance evaluation based on a leaf disc assay, and our results suggested that visual ratings of infected leaf discs provide a good estimate of sporangia numbers.