Contrasting aspects of the physical and physiological dormancy shown by seeds from different peach rootstocks

Abstract

Considering that cultivars of peach rootstocks selected to be propagated by seeds show variation in the degree of physiological dormancy and peculiarities regarding the limitation imposed by the endocarp, it is essential to define the cold stratification period and the ideal temperature to be used during the pre-germination treatment. Isolated for each cultivar, knowledge of these variables which will provide viability in the production of peach rootstocks via seeds, in the presence of the endocarp, at a larger scale. Two germination tests were carried out, in a completely randomized experimental design and 4 x 3 factorial scheme, with four replications, each one consisting of 25 endocarps. The first experiment was performed with four cultivars (Aldrighi, Capdebosq, Okinawa Roxo and Tsukuba 1) and three stratification temperatures (1°C, 4°C and 7°C) for a period of 90 days. For the second experiment, the same cultivars were used, two temperatures (7°C for ‘Aldrighi’ and ‘Capdebosq’ and 4°C for ‘Okinawa Roxo’ and ‘Tsukuba’) and three stratification periods (40, 80 and 120 days), followed by sowing in substrate under greenhouse conditions for a period of 45 days, with subsequent endocarp breaking and re-sowing. The pre-germination treatment at 7°C for 90 days is sufficient to obtain high germination percentage of ‘Aldrighi’ and ‘Capdeboscq’ seeds in the presence of the endocarp. Under the stratification conditions tested, the seeds of ‘Okinawa Roxo’ and ‘Tsukuba 1’ require rupture of the endocarp to reactivate the germinative embryonic process.