Response of some plum cultivars to abiotic stress

Significant changes in climatic factors have been observed in recent years which necessitates the introduction of new cultivars into production after their preliminary testing regarding their reaction to different climatic anomalies. During 2019-2021, the resistance to winter cold (in lab conditions at -15, -20 and -25°С, for 5 h), late spring frosts and summer drought of 10 new plum cultivars introduced in Bulgaria from Germany were evaluated. The trees were grafted on seedling rootstocks (Prunus cerasifera Ehrh.) and planted in an experimental plantation in the spring of 2011. The cultivar ‘Stanley’ was used as a control. The results indicated significant differences among evaluated cultivars. From the analysis of the results at the three freezing levels it can be concluded that ‘Stanley’, ‘Top 2000’, ‘Topend Plus’, ‘Tophit Plus’ and ‘Toрper’ have relatively higher resistance to low winter temperatures. ‘Stanley’, ‘Topking’, ‘Tophit Plus’ and ‘Top 2000’ showed low damage to flower buds or pistils (between 14.3 and 38.5%), while ‘Toptaste’, ‘Topgigant Plus’ and ‘Topper’ proved to be very sensitive to spring frost (-3°С) − damages varied from 59.6 to 75.8%. The highest drought resistance, determined by leaf water potential and visual observations, showed ‘Topstar Plus’ and ‘Topper’, and the most sensitive were ‘Topfirst’, ‘Toptaste’ and ‘Topgigant Plus’.