Seed washing, exogenous application of gibberellic acid, and cold stratification enhance the germination of sweet cherry (Prunus avium L.) seed

Seed germination in sweet cherry (Prunus avium L.) is a slow and lengthy process which has delayed breeding efforts. In this study, seed from ripe fruit of the sweet cherry cultivar ‘Lambert’ were collected and, after removing the endocarp, various dormancy-breaking treatments such as seed washing, the application of exogenous gibberellic acid (GA3), or cold stratification were evaluated for their ability to enhance the percentage and rate of seed germination. The results indicated that seed washing was necessary to break dormancy in sweet cherry. The seed germination percentage and rate improved to 26.5% and 1.17 seed d–1 simply by washing the seed for 24 h. The application of up to 500 mg l–1 GA3, in addition to a seed washing treatment, further improved both the seed germination percentage and rate to 47.1% and 1.9 seed d–1, respectively. Although the seed germination percentage improved as a result of 6 weeks of cold stratification, a longer cold period (8 weeks) was required to obtain the maximum rate of germination. The application of higher concentrations of GA3 and longer periods of cold storage did not result in further improvements in the seed germination percentage or rate.The highest germination percentage (61.2%) was obtained following seed washing for 24 h, followed by 500 mg l–1 GA3 treatment, then 6 weeks of cold stratification, which was higher than the germination percentage in the control treatment (0%). The highest rate of seed germination was observed following 24 h of seed washing, then 1,000 mg l–1 GA3 treatment and 8 weeks of cold stratification (3.8 seed d–1), but this combined treatment did not differ significantly (P = 0.05) from seed washing, 1,000 mg l–1 GA3, and 6 weeks of cold stratification (3.6 seeds d–1).