Efficient method of transporting coconut (Cocos nucifera L.) zygotic embryos for cryopreservation of plumules by encapsulation/dehydration

Coconut is both socially and economically important crop in tropical and subtropical countries, thus the conservation of existing diversity of its germplasm is vital to maintain biodiversity, sustain crop production and utilisation of germplasm for crop improvement strategies. The recalcitrant storage behavior and large size of the coconut seed make it impossible to use as a germplasm storage material. Cryopreservation is an ideal means of long-term storage of germplasm which offers long-term storage capability with minimal storage space and maintenance requirements. The coconut embryo has been now adapted by various researchers for the purpose of germplasm exchange and it is now being routinely applied in germplasm collection and exchange activities with sufficient germination rates. The aim of the present study was to determine the effect of different coconut embryo transport/ storage methods [as solid endosperm plugs under cold temperature, embryos cultured in Solidified Agar Medium (SAM) or KCI solution under room temperature] on cryopreservation of plumules using encapsulation/dehydration method. The results revealed that plumules excised from embryos transported/stored in SAM and pretreated with 1.0M sucrose could by cryopreserved with 71.8% survival and 56% recovery rates. The survival and recovery could be further increased up to 77.5% and 65% respectively by supplementation of 1.0M sucrose with 20 µM ABA

Androgenic potential in coconut (Cocos nucifera L)

Conditions for induction of androgenesis in coconut cv. Sri Lanka Tall were studied. Anthers collected from inflorescences at four maturity stages were given heat (38_C) or cold (4_C) pretreatments for 1, 3, 6 and 14 days, either prior to or post inoculation. Three different basal media and different anther densities were also tested. Androgenesis was observed only in anthers collected from inflorescences 3 weeks before splitting (WBS) and after a heat pretreatment at 38_C for 6 days. Modified Eeuwens Y3 liquid medium supplemented with 100 lM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.1% activated charcoal and 9% sucrose was effective in inducing an androgenic response. The lowest anther density tested, 10 per petri plate, was found to be the optimal density. When androgenic calli or embryos were subcultured to Y3 medium containing 66 lM 2,4-D, followed by transfer to Y3 medium without plant growth regulators and finally to Y3 medium containing 5 lM 6-benzyladenine (BA) and 0.35 lM gibberellic acid (GA3), plantlets regenerated at a frequency of 7%. Histological study indicated that the calli and embryos originated from the inner tissues of the anthers. Ploidy analysis of calli and embryos showed that they were haploid. This is the first report of successful androgenesis yielding haploid plants from coconut anthers. (Résumé d'auteur