Effects of an in vitro maturation treatment on plant recovery from avocado zygotic embryos

An efficient protocol for in vitro maturation of very immature, <10 mm, avocado embryos has been developed. The efficiency of plant recovery as well as the quality of the resulting plants was greatly improved by including a maturation phase prior to induction of germination. The influence of different factors, such as the gelling agent, organic supplements or abscisic acid, on embryo maturation and subsequent germination was tested. Optimum conditions were met when maturation was carried out in B5m medium supplemented with the Jensen's amino acids, an extra 88 mM sucrose and 6 g l−1 agar as gelling agent. At these conditions, embryos which had been collected 68 days after pollination germinated at a 65% rate in solid medium, giving rise to healthy and vigorous plantlets. Anatomical differentiation and storage product accumulation occurring during the in vitro maturation phase were studied by means of histological techniques. Results obtained revealed that, at the end of the in vitro maturation period, embryos resembled the pattern previously established for avocado embryos matured under in vivo conditions: histodifferentiation had been accomplished and starch granules and protein bodies were abundant.