Alves, S. A. O. et al. 4

J. Biotec. Biodivers. v. 2, N.2: pp. 1-6, May. 2011

CI-2061 and Cj-2141 presented 20% and 6.6% of score 6, respectively. The others two varieties did not present score 6 (Figure 6).

Figure 6 - Percentage of in vitro germination of embryos of the four varieties of interspecific hybrids of oil palm ( Elaeis oleifera x Elaeis guineensis ) on MS medium + 0.5mg L NAA and BAP (T3). Stages are represented by scores (Figure 1). Values obtained at 60 days of culture.

The presence of plant growth regulator on the MS medium decreases the efficiency of conversion of embryos to the score 6. The behaviour of embryos was similar on the MS and ½ MS medium.

DISCUSSION

During the experiments, the varieties CI-2061 and Cj-2141 obtained the best results on MS medium and ½ MS and these results did not depend on the presence or absence of plant growth regulators. However, the other two varieties Cj-502 and Cj- 494 did not present good results independently of culture medium. Different varieties of rice submitted to the same medium also obtained different answers of regeneration from embryogenic callus (Khatun et al., 2003; Islam et al., 2004). The different answers observed among varieties reflect genotype-dependent.

Although, these varieties have the same origin ( E. oleifera x E. guineensis ) they are different and when submitted to the same medium, it is possible to determine the genetic superiority of several varieties. The genetic superiority of the variety to one determined characteristic can be revealed when this variety is cultivated in some nutritive medium with different combinations of plant growth regulators (Fantini Junior and Graça, 1990; Alves, 2007). The tissue culture is an important

tool for genetic breeding to the identification of genotypes that show high stability (i.e. genotypes that have high adaptability in general, to be able to produce very well in the different conditions of the environment) (Cruz and Regazzi, 2001).

The embryos cultivated on the MS and ½ MS medium, both supplemented with 0.5 mg.L BAP and NAA obtained inferior results when it compared with those cultured on medium free of these regulators. This inhibitory action of plant growth regulators (0.5 mg. L BAP and NAA) can indicate that embryos are in mature or cotyledonary stage because in this phase it synthesizes endogenous hormones that are need to complete development (Lemos, 2003; Alves, 2007).

Moreover, the presence of charcoal activated in culture medium can had decreased the action of plant growth regulators (Teixeira et al., 1993; Alves, 2007). The charcoal activated promotes the adsorption of several substances such as plant growth regulators. It is possible that the increase of the levels of growth regulators could result in some effect.

During the conversion process of zygotic embryos in seedlings of açaí palm ( Euterpe oleracea Mart.) cultured on MS medium with 0.25 % charcoal activated also it was verified no effect of growth regulators at the formation process of seedlings from zygotic embryos (Cavalcante, 2001). On the other hand, the formation of oil palm seedlings in MS medium, it was verified the need of include 2.5 mg.L

2.4 - D for the suitable formation of the plants, using culture medium free of charcoal activated (Kanchanapoom and Domyoas, 1999).

Different results were observed in the formation of seedlings of coconut palm ( Cocos nucifera L.) which was obtained complete plants after 75 days using MS medium with 0.1 mg.L NAA and BAP (Silva, 2002).

After 60 days from the inoculation of embryos in MS or ½ MS medium, the varieties CI-2061 and Cj-2141 formed seedlings with leaves and roots (Figure 7). In Euterpe oleracea , seedlings were obtained at 30 days of culture in MS medium in the absence of growth regulators (Cavalcante, 2001).