Effect of the embryo genotype on the chilling requirement for overcoming peach seed dormancy

Abstract

Peach seeds need chilling temperatures to overcome dormancy. The physiological bases of peach seed dormancy and bud break chilling requirement are considered strongly related, and this relationship could be used for early selection of low chilling genotypes. Peach seeds germinated more quickly under alternating than under constant temperatures. We studied the effect of the embryo genotype on the chilling requirement for seed germination. The seeds evaluated were obtained from the low chilling peach ‘Campinas-1’, which was either open-pollinated or crossed with the high chilling cultivar ‘Miraflores’. The open pollinated ‘Campinas-1’ trees were surrounded by low or very low chill cultivars. The seeds (without the endocarp) were conditioned in sealed, transparent, polyethylene bags containing moist germination paper. The bags were placed in the dark in a growth chamber that alternated between 5 and 10°C every two days. Germination percentages were grouped into four-day classes. Seeds of open-pollinated ‘Campinas-1’ began to germinate twenty days after stratification and reached about 80% germination in the following two days. The germination of ‘Campinas-1’ × ‘Miraflores’ seeds began after 25 days of stratification, reaching 80% after 40 days of stratification. The seeds of the open-pollinated ‘Campinas-1’ germinated over a short period of time (from the 20th to the 27th day), whereas the hybrid seeds had a wider interval of germination time (24th to 47th day), showing the quantitative effect of the seed dormancy trait. The results indicate a strong effect of embryo genotype on the chilling requirement of the seeds, encouraging the selection of low chilling requirement genotypes based on seed dormancy. The alternation of temperatures favourable for overcoming dormancy with temperatures favourable for seed germination can be useful to screen genotypes with fewer differences in chilling requirement.