M2

Origin History and Agronomic Importance

The M2 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 component Teleki 8B (a hybrid of Vitis berlandieri and Vitis riparia species) and the paternal form 333 E.M. (an interspecific hybrid of Vitis vinifera and Vitis berlandieri). As the main agronomic characteristics displayed by this rootstock variety, medium levels of resistance to drought, chlorides, and iron chlorosis have been recorded. The M2 rootstock demonstrates high yield parameters of mature canes in mother vineyards and promotes the formation of high-quality grafted planting material.

Ampelographic Description of M2 Rootstock Variety

The morphological characteristics of the rootstock were recorded in detail by experts during the standardized ampelographic evaluation according to the international OIV descriptors:

• Young shoot (tip): The young shoot tip is completely closed. Anthocyanin pigmentation on the tip is completely absent. The density of prostrate hairs on the tip is medium, while the density of erect hairs is rated as high. On the nodes of the young shoot during the flowering period, erect hairs are either completely absent or extremely sparse, and they are completely absent on the internodes. Prostrate hairs on the nodes and internodes of the young shoot during the flowering phase are either absent or barely perceptible. Tendrils are long, forming sequentially in groups of two or fewer. Internodes of the developing shoots are long, and their diameter has medium values.
• Young leaf: The upper surface of the fourth formed young leaf blade is green. The lower surface of the leaf between the main veins exhibits a low density of prostrate hairs, while erect hairs are absent. Prostrate hairs on the main veins on the lower side are absent, but a high density of erect hairs is recorded.
• Mature leaf: The leaf blade is characterized by a medium size and a cuneiform shape. The leaf is practically entire and consists of a single lobe. The upper surface of the blade features a medium green coloration. Anthocyanin pigmentation of the main veins on both the upper and lower surfaces of the leaf appears exclusively at the petiole point. The profile of the blade in cross-section is flat and even, with no depression or blistering of the upper surface. The teeth have a medium length and a mixed shape combining straight and convex sides. The petiole sinus is very open, U-shaped at the base, with no specific morphological anomalies. Lateral sinuses are completely absent. The length of the petiole is equal to the length of the median vein of the leaf. Prostrate and erect hairs are completely absent on the petiole.
• Woody shoot: The canes are circular in cross-section. The surface of the shoot is smooth, without hairs and without the formation of lenticels.
• Flower: The M2 rootstock variety develops inflorescences with a purely male flower type.

Features of Viticultural Nursery Practice

The M2 grapevine rootstock is distinguished by an exceptionally high shoot vigor in mother vineyards and is very 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 high. The rooting capacity of cuttings in commercial field nurseries is medium. When producing grafts with scion varieties of Vitis vinifera, the M2 rootstock demonstrates a high intensity of callus formation and an excellent ability to form a complete graft union at the junction of the components.