Testing of wood hardiness to winter freezes in selections from progenies of Cerapadus × Prunus avium L. crosses

Abstract

Winter hardiness of genotypes pre-selected from Cerapadus × Prunus avium L. crosses was studied for 3 years (2000–2002) in comparison with clonal cherry rootstocks, presently grown in the Czech Republic using artificial freezing of the budwood applied just after the phase of deep dormancy. With a temperature drop to freezing, both the mean and the maximum rate of general frost injury was markedly increased. The greatest damage of the tested material (roughly at the level of LD 50 on the average) occurred after the application of combined low temperatures –25°C for 4 hours + –20°C for 66 hours. The results of laboratory tests were compared with the damage of natural frost that occurred during the first half of January, 2002. The single observed years did not differ from each other in the extent of injury, on the average. From standard cherry rootstocks, P-HL-B was generally the most sensitive to freeze injury. Its weak winter hardiness was approximately the same, or even somewhat worse, than that of rootstock Colt. The rootstock P-HL-C was classified as medium sensitive to winter frosts, while rootstock P-HL-A was scored as winter hardy. The average frost injury score of all 48 selected Cerapadus × Prunus avium L. genotypes included in the study was 6.7, whereas that of all control cherry rootstocks was only 5.9. According to the results of this study, the tested genotypes were classified into 5 groups with different classes of frost resistance or susceptibility. The most frequent was the class of medium resistance. The following five genotypes were the most winter hardy: CPH VODÁRNA, CPH 43, CPH 17, CPH 22 and CPH 49. On the basis of the obtained results, suggestions for improving testing procedures are also given.