Title:

Comparison of SPAD Values and Fungal Disease Level of Canadice and Mars Grape Varieties Growing on Different Training Systems

The objective of this study was to compare the impact of two different training systems, vertical shoot positioning (VSP) and modified Munson (MM), on grapevine’s physiological parameters such as SPAD measurements for greenness. The study was conducted in a vineyard planted at the University of New Hampshire (Woodman Research Farm, Durham, NH). Two cold hardy seedless table grape varieties, Canadice and Mars, growing on two training systems, VSP and MM, were followed throughout the 2019 growing season. We conducted scouting of grapevines on a weekly basis, from flowering to harvest, to monitor the appearance of fungal diseases. Disease severity scorings were done using a rating scale of 0 – 4, with 0 “means no symptoms” and 4 means “symptoms visible in entire plant”. SPAD measurements were recorded weekly, from flowering to veraison, on two fully developed leaves per vine. The fungal diseases started with stem anthracnose in the month of June 2019, at the rating of “1” until the end of July 2019. Leaf anthracnose and Leaf black rot started appearing in both Canadice and Mars varieties, with the rating of “1” in some plants from the month of July 2019 until September 2019. Leaf downy mildew started appearing in both varieties with a rating of “1” from the mid-August until harvest at the rating of “3”. Grape black rot started appearing from the starting of August mainly in Canadice until harvest season at the rating of “1”. The SPAD values appeared to be greater for MM compared with VSP in both cold-hardy table grape varieties.

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