Abstract
Sweet cherry (Prunus avium L.) is one of the economically important fruit crops worldwide. However, late spring frosts occurring in some years can significantly impact sweet cherry productivity through organ and tissue destruction caused by frost damage, and very little is known about frost tolerance or susceptibility of new cultivars. Differential thermal analysis (DTA) was, therefore, used to examine the exothermic characteristics (temperatures at which 50% of the flower buds were killed - mLTE values) of the flower buds belonging to members of the genus Prunus - 6 Prunus avium cultivars ('Noir de Guben', 'Bigarreau Gaucher', 'Merton Late', 'Merton Bigarreau', 'Van' and wild genotype). In the study, mLTE values of flowers of six cherry cultivars were determined at different floral bud developmental stages such as side green, green tip, open cluster, first white and full bloom under laboratory-based freeze assays for consecutive two years. The mLTE values of flower buds changed according to both different floral bud developmental stages and sweet cherry cultivars. In our findings, the mLTE values of flower buds in all cultivars generally occurred at higher temperatures in the open cluster stage, whereas the mLTE values of the flower buds in the first white stage occurred at lower temperatures, and therefore, these results are not only controversial in terms of previous frost tolerance studies, but also the first findings to be reported in literature. Considering the two-year average, the temperatures causing mLTE values for flower buds was -1.58 to -3.74°C at the side green stage, -0.94 to -3.51°C at the green tip stage, -0.41 to -1.96°C at the open cluster stage, -2.30 to -11.52°C at the first white stage and -2.37 to -9.80°C at the full bloom stage in the range of six cultivars. In laboratory-based freezing experiments, the 'Van' cultivar were least affected by low temperatures, followed by 'Bigarreau Gaucher' cultivar and wild genotype. 'Merton Late' cultivar, on the contrary, was the most sensitive cultivar to low temperatures, followed by 'Noir de Guben' and 'Merton Bigarreau'. These results can be valuable in predicting possible frost damage at different developmental stages of the flower buds in sweet cherry.
Comparative transcriptomic analysis reveals novel roles of transcription factors and hormones during the flowering induction and floral bud differentiation in sweet cherry trees (Prunus avium L. cv. Bing)