Instability of grape phenology in the late 20th – early 21st century in the northern area of industrial cultivation

The climate warming and destabilization are currently recognized as signifi cant factors aff ecting the development of viticulture worldwide. To mitigate the production risks of various agricultural crops, the prospects of less productive but more stable early varieties are being explored. Plant phenology serves as a sensitive indicator of climate changes. The study involves observations on the length of the productive period and phenological data of 30 grape varieties, obtained within 25 years or more from 1981 to 2022. The sample is diverse in terms of taxonomic affi liation, cultivation methods, intended use, and ripening periods. The present study is aimed at comparing stability of the length of the productive period for 30 grape varieties from the Potapenko Donskaya Ampelographic Collection during the periods of 1981‒2001 and 2002-2022. The standard deviations of the length of the productive period were calculated in order to assess instability for each period. The Wilcoxon criterion revealed that, on average, the length of the productive period for 30 grape varieties from 2002 to 2022 decreased by 10 days compared to the period from 1981 to 2001 (from 139 to 129 days), while the standard deviation increased from 8.2 to 10.9 days. The most stable length of the productive period was observed for ultra-early, very early, medium, and medium-late varieties, whereas the least stable varieties included early and early-medium varieties which ripe between the third decade of August and the fi rst decade of September. The instability in the length of the productive period of early and early-medium varieties can be attributed to the sharply increased variability of August temperatures and the rise in the number of days with temperatures exceeding 35 °C, which produces hindering eff ect on the development of grapes. The impact of the high temperatures observed in July and August was mitigated by an extended duration of autumn periods with temperatures over 10 °C for the mid- and mid-late grape varieties.