Effect of bead nutrient composition on regrowth of stored vitro-derived encapsulated microcuttings of different woody species

Aseptic encapsulation in a sodium-alginate bead containing different nutritive solutions of microcuttings (uninodal explants excised from micropropagated shoots) of 10 different genotypes from four different woody species (Actinidia deliciosa, kiwifruit, cv Hayward and Tomuri; Malus spp,, apple, rootstock M.26 and cv Starkspur Red and Wellspur; Olea europea, olive, cv Canino, Moraiolo, Ascolana tenera and Dolce Agogia; Rubus Idaeus, raspberry, Selection 1401) was investigated. The aim of the study was to evaluate the best nutritive formulation of the bead among seven different solutions, made of inorganic and organic compounds, growth regulators and sucrose, alone and combined, in order to maintain viability throughout 30 days of storage at 4 degrees C and subsequent regrowth ability of the encapsulated microcuttings on agarized medium, in view also of the possibility of inserting this storage phase in micropropagation cycles of these species. Olea plants gave interesting viability rates from 47.6 to 100% (according to cultivar and nutritive solution of the bead) immediately after storage, but the least satisfactory results in terms of regrowth, because of probable inadequacy of the culture medium. Actinidia, Malus and Rubus, instead, gave maximum rates in regrowth of 90.6% ('Hayward'), 83.3% ('M.26') and 83.4% ('Sel.1401'), respectively, and in sprouting of 62.5% ('Tomuri'), 75.0% ('M.26') and 77.2% ('Sel.1401'), respectively. Furthermore, encapsulated Rubus microcuttings proved usable also as synthetic seeds, with a maximum rooting land conversion) rate of 60.7%.