The embryo dormancy in apple is a limiting factor in breeding programs with this species. Thus the present work was carried out in order to study the in vitro germination of M9 apple dormant embryos, originated from the Experimental Station of São Joaquim (EPAGRI/SC). The embryos, excised from mature seeds were inoculated in the basal culture medium MS supplemented with of sucrose (30 g.L-1), coconut water (15%), casein hydrolysate (CH) (500 mg.L-1), AIA (0 and 14 µM); GA3 (0 and 1.5 µM); and three citokinins sources: (Kin (5 µM); 2iP (12 µM) and BAP (4 µM). The culture medium was gellified with agar (6 g.L-1). The cultures were maintained in the dark during 10 days, then transferred to growth room under 16 hours of light period, 25 ± 2°C, temperature, and 19 µE.m-2.s-1 of luminous radiation. The results showed that the highest value for embryo germination (75%) was obtained in MS culture medium supplemented with CH, AIA (14 µM), GA3 (1.5 µM), and Kin (5 µM). When, in this treatment the Kin was replaced by BAP (4 µM), it was observed the callus induction and the subsequent proliferation of buds and shoots, reaching values of 2.3 shoots/embryos and 12.3 buds/shoot. The length of shoots was 4 cm, without statistical differences between the different treatments. The highest percentage of callus induction occurred in culture medium supplemented with AIA, Kin, and 2-iP. The culture medium MS half strength supplemented with CH, coconut water and free of growth regulators resulted in values of 25% of germination. The root number was highest in the culture medium supplemented with AIA (14 µM), GA3 (1.5 µM), and CH. The average root length (4.0) was not affected by any particular treatment. Thus, this technique is an efficient alternative to the cool treatments for dormancy suppression.
in vitro germination; citokinin; GA3; caseine; coconut water
