Winter resistance of new perspective varieties and elite forms of pear of the Institute of Horticulture, NAAS of Ukraine
DOI: 10.35205/0558-1125-2023-78-41-44
UDC 634.13:631.526.32:632.111.5
WINTER RESISTANCE OF NEW PERSPECTIVE VARIETIES AND ELITE FORMS OF PEAR (PIRUS COMMUNIS L.) OF THE INSTITUTE OF HORTICULTURE, NAAS OF UKRAINE
Yu.B. KHODAKIVSKA, PhD
Institute of Horticulture, NAAS of Ukraine, 03027, Kyiv-27, 23, Sadova st., е-mail: lab.plod@ukr.net
The results of determining the winter and frost resistance of new promising varieties of pears of the IH NAAS selection Vezha muscatna, Kytaiskyi likhtaryk, Panianka and elite forms 4-24 (Dekanka muscatna), 4-79 (Vodokhreshche), 17-98 (Suvenirna), 17-103 (Olkhotivska). Temperatures of -25...-30 °C during the most important periods of pear wintering are not devastating for all studied varieties and forms. Low temperatures (-25...-30 °C) damage all the tissues of the tops of the shoots somewhat more than the middle part. In addition, damage by the pear leafhopper (Psylla ріricola Forst.) contributed to the decrease in winter hardiness of Panianka, Kytaiskyi likhtaryk and Vyzhnytsia varieties and forms 17-98 (Suvenirna). According to the complex of features included in the concept of winter hardiness, the Vezha muscatna variety and the elite forms 4-24 (Dekanka muscatna) and 4-79 (Vodokhreshche) stand out on the positive side.
The freezing of tissues of the sub-bud zone of generative buds has a significant practical effect on the formation of the next year's harvest. This zone is a kind of biological safeguard against premature sprouting of buds in January-February. Previous studies have also established that in the sub-bud zone, at the time of natural dormancy, in the zone of the conducting vessels connecting the bud to the shoot, the xylem part, where the vascular bundle will then pass, is filled with unstructured parenchyma cells. The formation of a vascular bundle in this zone is preceded by a double restructuring - the transformation of parenchymal cells into cambial cells (long-term warming to +5…+10 °С in February), and the latter into spiral vessels (beginning - mid-March). Restructuring periods are very sensitive to low temperatures, and if at this time they drop to -10...-12 °С, a vascular bundle is not formed, without which the development of a fruit bud is impossible, which leads to a significant decrease in yield. These conclusions are also confirmed by our observations: in the formation of the pear crop, the coincidence of unfavorable weather conditions in January-February and their influence on generative buds are sometimes more noticeable than during spring frosts, which in our conditions occur mostly after the pear has blossomed, and yarrow is more frost-hardy than flowers.
Key words: pear, variety, frost resistance, winter resistance, bark, cambium, wood, core, bud.
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