M3

Origin History and Agronomic Importance

The M3 grapevine rootstock was bred in Italy by selectionists at the Council for Agricultural Research and Agricultural Economy Analysis (CRA). Official admission of the rootstock to the National Register of Grape Varieties took place on May 15, 2014. The parental pair used in crossbreeding is represented by the maternal genotype R 27 and the paternal component Teleki 5C, both being interspecific hybrids of Vitis berlandieri × Vitis riparia. The primary advantage of this rootstock variety lies in its exceptionally high resistance to drought, combined with medium levels of resistance to chlorides and iron chlorosis. Based on these characteristics, the M3 rootstock is recommended for drought-prone regions and soils with a moderate risk of iron chlorosis and average chloride levels. The M3 rootstock features early dates of budburst, flowering, and wood maturity.

Ampelographic Description of M3 Rootstock Variety

The morphological characteristics of the rootstock were recorded in detail based on the official state evaluation according to the international OIV descriptors:

• Young shoot (tip): The young shoot tip is completely closed. A diffuse anthocyanin pigmentation of medium intensity is present on the tip. Prostrate and erect hairs are completely absent on the tip. On the nodes and internodes of the young shoot during the flowering period, prostrate and erect hairs are either completely absent or extremely sparse. Tendrils have a medium length, forming sequentially in groups of two or fewer. Developing internodes are long with a medium diameter.
• Young leaf: The upper surface of the fourth formed young leaf blade is green. Both prostrate and erect hairs are completely absent on the lower surface of the young leaf (both between the veins and on the main veins themselves).
• Mature leaf: The leaf blade is characterized by a medium size and a cuneiform shape, with three distinctly pronounced lobes. The upper surface of the blade features a medium green coloration. Anthocyanin pigmentation of the main veins on the upper surface appears exclusively at the petiole point, and is completely absent on the lower surface. The profile of the blade in cross-section is slightly contorted, with no blistering or depression of the tissue. Lateral sinuses are deep. The teeth are small and short relative to the width of their base, showing a mixed shape with straight and convex sides. The petiole sinus is open, with a V-shaped base and no specific morphological anomalies. On the lower surface of the leaf, a very low density of prostrate hairs is present between the veins and on the veins themselves; erect hairs are absent between the veins, but a low density of erect hairs is recorded on the veins on the lower side. On the upper surface of the leaf, prostrate hairs along the main veins are absent, but sparse erect hairs are detected. The petiole is slightly shorter than the median vein and is completely devoid of prostrate and erect hairs.
• Woody shoot: The canes are circular in cross-section. The surface of the shoot is smooth, completely devoid of hairs and lenticels.
• Flower: The M3 rootstock variety develops inflorescences with a functionally female flower type.

Features of Viticultural Nursery Practice

The M3 grapevine rootstock demonstrates a very high shoot vigor in mother vineyards and is extremely prone to intensive lateral shoot development during the growing season. The agronomic productivity of mother vineyards in terms of high-quality mature wood yield per hectare is rated as medium. The rooting capacity of cuttings in commercial field nurseries is medium. When producing bench or field grafts with scion varieties of Vitis vinifera, this rootstock shows medium parameters of callus formation and successful graft union development.