Vitis 35 (1), 23-28 (1996) Preliminary results on the use of a modified point quadrat method for estimating canopy structure of grapevine training systems by S. PoNI, BARBARA REBuccr, E. MAGNANINI and C. INTRIERI Dipartimento di Colture Arboree, Cattedra di Viticoltura, Universita di Bologna, Bologna, Italia. S u m m a r y : The reliability of a modified point quadrat method designed to describe the structure and seasonal canopy dynamics of the training systems simple curtain (SC) and traditional spur-pruned cordon (SPC) was tested in a two-year study. The method relies upon an unbiased sampling procedure as each canopy insertion is first identified within a ground-projected area by a random number generation routine (RND). From each insertion, the height of each contact with either leaves or clusters is then recorded along the vertical axis. Although the method suffered from a somewhat low percentage of effective insertions early in the season, the total leaf area-to-surface area ratio and the leaf layer number calculated for both canopy types are in accordance with those reported by others for high vigour canopies. Canopy dynamics showed an asymmetric growth in the SC starting at bloom. Both trellises resulted in similar canopy density indices and a high correlation was found between total leaf area and total number of leaf contacts. K e y w o r d s : Vitis vinifera L., leaf area, training system, canopy density, canopy shape. Introduction Every grapevine training system displays a typical canopy structure, which in turn determines the microclimate within the canopy profile. Many biological processes of the utmost importance (total vine photosyn- thesis, bud differentiation, fruit ripening, and wood matu- rity) are thus closely related to seasonal canopy develop- ment. Also, the application of specific management op- erations (e.g. shoot topping and positioning, leaf removal) can modify the canopy of differently trained vines. The scorecard proposed by SMART et al. (1985) enables a visual assessment of various grapevine canopies on an index of 8 characters to which are assigned a maximum of 10 points each. Accordingly, a high score should ideally correspond to canopies with adequate gaps, low leaf layer number (LLN) and high cluster exposure. In a few cases canopy density has been estimated using indices like total leaf area- to-exposed canopy surface area (LNSA) or LLN, param- eters that have also been used for correlations with yield and quality (SMART 1985; INTRIERI 1987; SMART and RoBINSON 1991). Canopy assessment in grapevine has also been attempted via the "point quadrat" method developed by LEVY and MADDEN (1933) and then extensively used for Simple Curtain non-destructive estimation of foliage area index and incli- nation in grassland or other low-growing crops (WARREN WrLSON 1960; 1965). On vertical grapevine canopies, meas- urements have been taken by horizontally inserting a metal rod into the fruit zone using a grid pattern and then by recording contact points with leaves and clusters for each insertion to determine percent gaps, leaf layer number and percentages of interior leaves and fruit (SMART and SMITH 1988). The aim of the present study was to test the validity of a modified point quadrat method employing an unbiased random sampling to describe canopy structure and dynamic changes of two grapevine training systems that are becom- ing widespread in northern and central Italy. Materials and methods The trial was carried out in 1994-95 at the Settefonti experimental vineyard (Bologna, 44°52' N) on five-year- old Chardonnay/S04 vines trained to simple curtain (SC) and traditional spur-pruned cordon (SPC). The scheme of the two training systems is reported in Fig. 1. Two vines with good wood maturity from previous season's growth Spur-pruned Cordon Fig. 1: Cross sections and front views of vines trained to a simple curtain (SC) and a spur-pruned cordon (SPC). Correspondence to: Dr. S. PoNI, Universita di Bologna, Dipartimento di Colture Arboree, Cattedra di Viticoltura, Via Filippo Re 6, I- 40126 Bologna, Italy. Fax: 051-351500.