Báo cáo lâm nghiệp: "Micropropagation of hybrid walnut trees (Juglans nigra x Juglans regia) through culture and multiplication of embryos"

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Nội dung Text: Báo cáo lâm nghiệp: "Micropropagation of hybrid walnut trees (Juglans nigra x Juglans regia) through culture and multiplication of embryos"

Micropropagation of hybrid walnut trees (Juglans nigra x Juglans regia) through culture and multiplication of embryos C. D. Cornu Jay-Allemand Am6lioration des Arbres Forestiers, INRA, Ardon, 45160 Olivet, France rdor bres propagated by micropropagation, and 2) Introduction improve culture factors acting on shoot to development. Walnuts are very valuable trees for nuts and wood production, but we see a reduc- tion in the number of logs available for veneer. Although Persian walnut (Juglans Materials and Methods regia) and black walnut ((J. nigra) can be used, hybrids between these two species This study used half-sib hybrid nuts (J. nigra have better growth and wider adaptability. (no. 23) x J. regia) supplied by E. Germain (INRA, Bordeaux), collected in September Breeding programs are in progress at 1987. Embryonic axes (48) were isolated under INRA (Institut National de la Recherche sterile conditions and then introduced in vitro Agronomique, Bordeaux and Orl6ans) and into the medium defined by McGranahan et al. they need efficient methods of vegetative (1987). Three main steps have been determin- propagation. Micropropagation ed: 1) elongation of epicotyls and buds during 3 esta- was wk of darkness followed by 2 wk of 16 h of light blished in 1984 for ’Paradox’ (Driver and at 28°C; 2) multiplication by transferring nodes Kuniyuki, 1984) and recently for Persian from elongated shoots or clusters of buds every walnut (McGranahan et al., 1988). Pre- 2 wk (16 h light, 28°C); 3) rooting (not present- vious works have shown strong effects of ed in this paper). ageing and rejuvenation (Jay-Allemand et Two kinds of solidifying compounds (Difco- al., 1988), latent contamination, low reac- Bacto agar, 6 g/I, and Gelrite, 2.3 g/I) in 750 ml were compared. Then, instead of one jars tivity of buds or meristems on the esta- transfer onto a fresh medium after 2 wk of cul- blishment of mature selected clones. On ture, the addition of about 2 cm of a new liquid the contrary, with very juvenile material, medium without transfer was studied (double such as embryos, it is possible to avoid phase system, Viseur, 1987). these problems (Jay-Allemand and Cornu, was deter- The number of shoots (>5 mm) mined for each clone at the 3rd and 8th trans- 1986; Heile-Sudholt et al., 1986). fers, and the number of bud-clusters and The purpose of this study was: 1) to elongated shoots (>15 mm) at the 10th, 11th, estimate the ability of hybrid progeny to be l2th and 13th transfers.
Results shoots, usable for rooting, produced were every 2 wk to 100 bud-clusters. After 2 transfers, the development of The 48 clones which were cultivated clones and particularly callus formation under the same conditions show great increased significantly (1% level) in the variability in their bud-cluster development Gelrite (Table 11). If liquid medium did not and shoot elongation. After 3 and 8 trans- increase the mean number of elongated fers, we obtained a normal distribution of shoots, the E’ of those shoots longation clones (Fig. 1A and iB). Ranking of some significantly higher (Table III). was clones changed during this time but stabi- lized after the 8th transfer. Eight of the best clones were selected for bulk propa- Discussion and Conclusion gation. They were characterized by good development of leaves and elongation of shoots. The production of buds and The studies have shown that the micro- shoots during 3 transfers is summarized in propagation of juvenile walnut depends Table I. In 6 wk, the number of bud-clus- upon many factors. At a general level, ters multiplied by 1.5. An average of 60 characteristics of the medium are im-
in the cules and of availability variability water. This last effect could be associated with the positive action observed with liquid medium. Chun et al. (1986) obtained better results with poplar in liquid medium than with a gelified one. Nevertheless, some cases of vitrification appear after long-term culture in liquid medium. On the contrary, Viseur (1987), avoided vitrifi- cation in pear and increased bud produc- tion by adding liquid medium. All these phenomena should be connected with the metabolism of phenolic compounds, lignifi- cation or ethylene. With our system on walnut, studies are and will be conducted in these fields to determine the more im- portant medium factor. McGranahan et aG (1988) recommend- ed for Persian walnut micropropagation a 1 wk transfer interval for gelified medium. According to our results, and from a prac- tical point of view, results presented here clearly illustrate that some of the very expensive transfer work can be avoided by adding liquid medium to cultures. Final- portant. Results obtained with Gelrite ly, the great variability between clones, confirm our previous observations when also observed by Heile-Sudholt et aL we lost all material growing on agar (un- (1986), could limit the interest of bulk published data). Many different hypo- micropropagation. Complementary re- theses have been proposed to explain the search is needed to determine if the best influence of agar. These include the pres- clones for micropropagation are also the ence of inhibitors, rate of diffusion of mole- best for field plantations.
Ann. Sci. For. 43, 189- References (Juglans regia L.). mun 198 Jay-Allemand C., Cornu D. & Macheix J.J. Chun Y.W., Hall R.B. & Stephens L.C. (1986) (1988) Biochemical attributes associated with Influence of medium consistency and shoot rejuvenation of walnut tree. Plant Physiol. Bio- density on in vitro proliferation of Populus alba chem. 26, 139-144 x P. grandidentata. Plant Cell Tissue Cult. 5, McGranahan G., Driver J.A. & Tulecke W. 179-185 (1987) Tissue culture of Juglans. In: Cell and Driver J.A. & Kuniyuki A.H. (1984) In vitro prop- Tissue Culture in Forestry, Vol. 3, (Bonga J.M. agation of paradox walnut rootstock. Hort- & Durzan D.J., eds.), Martinus Nijhoff, Dor- Science 19, 507-509 drecht, pp. 261-271 Heile-Sudholt C., Huetteman C.A., Preece J.E., McGranahan G., Leslie C.A. & Driver J.A. Van Sambeek J.W. & Gaffney G.R. (1986) In (1988) In vitro propagation of mature Persian vitro embryonic axis and seedling shoot tip cul- walnut cultivars. HortScience 23, 220 ture of Juglans nigra L. Plant Cell Tissue Cult. 6, 189-197 Viseur J. (1987) Micropropagation of pear, Pyrus communis L., in a double phase culture Jay-Allemand C. & Cornu D. (1986) Culture medium. Acta Hartic. 212, 117-124 in vitro d’embryons isol6s de noyer com-