Development of a standard set of microsatellite reference alleles for identification of grape cultivars.

In order to investigate the comparability of microsatellite profiles obtained in different laboratories, ten partners in seven countries analyzed 46 grape cultivars at six loci (VVMD5, VVMD7, VVMD27, VVS2, VrZAG62, and VrZAG79). No effort was made to standardize equipment or protocols. Although some partners obtained very similar results, in other cases different absolute allele sizes and, sometimes, different relative allele sizes were obtained. A strategy for data comparison by means of reference to the alleles detected in well-known cultivars was proposed. For each marker, each allele was designated by a code based on the name of the reference cultivar carrying that allele. Thirty-three cultivars, representing from 13 to 23 alleles per marker, were chosen as references. After the raw data obtained by the different partners were coded, more than 97% of the data were in agreement. Minor discrepancies were attributed to errors, suboptimal amplification and visualization, and misscoring of heterozygous versus homozygous allele pairs. We have shown that coded microsatellite data produced in different laboratories with different protocols and conditions can be compared, and that it is suitable for the identification and SSR allele characterization of cultivars. It is proposed that the six markers employed here, already widely used, be adopted as a minimal standard marker set for future grapevine cultivar analyses, and that additional cultivars be characterized by means of the coded reference alleles presented here. The complete database is available at http://www.genres.de/eccdb/vitis/ Cuttings of the 33 reference cultivars are available on request from the Institut National de la Recherche Agronomique Vassal collection (didier.vares@ensam.inra.fr).

Shoot orientation affects vessel size, shoot hydraulic conductivity and shoot growth rate in Vitis vinifera L.

Vitis vinifera L. plants were grown in containers and each plant's single shoot was orientated upwards or downwards. Some plants were trained first upwards, then downwards, then again upwards (N-shaped plants). Vegetative growth was reduced in plants trained downwards compared to that in upward and N-shaped plants. Shoot growth rate slowed in downward shoot portions, but only after the apex had grown downwards for at least 10 internodes. Shoot hydraulic conductivity kh, measured after elimination of xylem embolisms, was lower in downward than in upward plants. In N-shaped plants kh was higher in the upward-growing shoot portions, and lower in the central, downward-growing portion. Shoot- and leaf-specific conductivities were also lower in downward than in upward shoot portions. Xylem cross-sectional area and xylem structure (number of wedges, number of vessels per unit xylem area) differed little in the three orientations. In contrast, vessel diameter and the sum of vessel cross-sectional areas were significantly smaller in downward than in upward shoot portions. These differences could explain the reduction in conductivity observed in the downward-orientated shoot portions. The measurements taken on N-shaped plants showed that the decreases in kh and in vessel size were a result of shoot orientation, not shoot bending.