Search

A bacterium has been isolated that initiates adventitious rooting when co-cultured under in vitro conditions with seedling-produced hypocotylary explants of slash pine (Pinus elliottii). Rooting efficiencies produced through bacterial-explant co-culture range from approximately 15% to greater than 90% over non-treated controls. Explant exposure to the root inducing bacterium has produced no obvious pathology in the regenerated plantlets. Seedling explants rooted by bacterial-explant co-culture have been successfully transitioned to ambient greenhouse conditions.

Peanut (Arachis hypogaea L.) somatic embryos were produced from the embryo axes of mature, dry seeds of cultivar GK-7. Percent embryogenic explants ranged from 88-100% using 10-40 mg/1 of 2,4-D in the induction medium. Neither 2,4-D concentration nor photoperiod during the induction period had a large effect on percent embryogenesis, mean number of embryos per explant, or embryo morphology. However, embryos obtained from cultures grown in the dark were easier to remove from the explant than those under a 16-h photoperiod. Somatic embryos developed on the epicotyl portion of the embryo axis, primarily on the young, expanding leaves. A survey of 14 genotypes indicated that genotype had a large influence on embryogenic capacity, with all genotypes being embryogenic to some extent. The ability to recover somatic embryos from axes of harvested, stored seeds represents significant advantages for the establishment of peanut embryogenic cultures, including the use of simple sterilization procedures and a constant source of explant tissue.

Somatic embryos were produced from peanut (Arachis hypogaea L.) immature zygotic cotyledons. Comparisons were made of the level of α-naphthaleneacetic acid during induction, nitrogen formulation of the medium, and photoperiod. Over 70% embryogenesis was obtained regardless of NAA level used. Percent embryogenesis and number of embryos were markedly lower in explants induced on NAA compared to 2,4-D. Embryo production was not greatly affected by either the use of Murashige & Skoog versus Finer & Nagasawa salts or light versus dark culture conditions. However, embryo morphology was noticeably affected by photoperiod. Embryos produced under a 16 h photoperiod were tough, woody and difficult to separate for subsequent germination and conversion. Those produced under a 0-h photoperiod were succulent and pliable.

Hypocotylary explants obtained from 30- to 40-day-old slash pine (Pinus elliottii, Engelm.) seedlings treated with 6-benzylaminopurine produced multiple buds that eventually elongated into axillary shoots. The explants were pulse treated (45-s dip) with 6-benzylaminopurine (22.2, 111, 222 μM) plus a control and cultured on three different basal media containing activated charcoal (0.5% w/v). Hormonal concentration and basal medium were compared for the number and size of axillary shoots induced after 12 and 29 days. The greatest number of axillary shoots was produced by explants that were pulse treated with 111 μM 6-benzylaminopurine and cultured on Gresshoff and Doy medium. The axillary shoots were fewer in number per explant than shoots previously reported resulting from hormonally induced advantitious buds of slash pine, but the axillary shoots developed more rapidly.