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  • Author or Editor: R. M. Skirvin x
  • Journal of the American Society for Horticultural Science x
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Chimeral `Thornless Evergreen' (CTE), (Rubus laciniatus Willd.) somaclones selected in 1983 and field planted in 1985 were reexamined in 1992 for various vegetative and reproductive characteristics. Two major types of thornless (prickle-free) plants, intermediate-sized (`UI 6-6' = `Everthornless') and dwarf (`UI 6-4'), originally selected from a chimeral thornless parent plant, were compared with thorny plants. The intermediate and dwarf somaclones have maintained their distinctive habits over 7 years' growth in the field, indicating that their growth habits are stable and not a transient effect of tissue culture. Although the thornless somaclones remained thornless, the degree and type of prickle-like structures varies considerably, indicating that the thornless gene (S te) does not entirely suppress the production of prickles, but apparently alters their development. Increasing suppression was directly related to increasing dwarfism, suggesting a link between thornlessness and internode length.

Free access

Abstract

In vitro techniques were developed to regenerate plantlets (calliclones) from callus of scented geraniums (Pelargonium spp.). Calliclones were compared to plants derived from stem, root, and petiole cuttings of 5 cultivars. Plants from stem cuttings of all cultivars were uniform and identical to the parental clone. Plants from root and petiole cuttings were more variable with the amount of variation dependent upon cultivar. High variability was associated with calliclones. Aberrant types included changes in plant and organ size, leaf and flower morphology, essential oil constituents, fasciation, pubesence, and anthocyanin pigmentation. Calliclone variation was dependent upon clone and age of callus. Variability in calliclones was due to segregation of chimeral tissue, euploid changes, and heritable changes which may involve individual chromosomal aberrations or simple gene mutations. Variability of calliclones might be exploited for improvement of vegetatively propagated crops especially highly polyploid, sterile lines.

Open Access

Abstract

The discrepancy in seed set observed in reciprocal crosses of red (Rubus idaeus L.) and black (R. occidentals L.) raspberries verifies unilateral incompatibility. The strength of the incompatibility varies between cultivars; some red × black crosses yield a small percentage of seed set by simple cross-pollination, while others produce almost no seed. Although black cultivars have shorter pistils than red cultivars, the role of this factor in incompatibility is unknown. Bud pollination and heat treatments increased seed set in some normally incompatible red × black crosses.

Open Access

Abstract

Embryos extracted from developing apple fruit were cultured in vitro. Immature embryos (up to 4 weeks post anthesis), cultured without their testa and endosperm, produced only callus tissue. Six and a half-week-old embryos produced multiple shoots and the percentage of embryos producing shoots rather than callus tissue increased with time. Ten and a half-week-old embryos produced the highest number of shoots per embryo, after which a decrease in multiple shoot formation was observed with mature (14 weeks post anthesis) embryos producing 1 shoot and 1 root per embryo. Simultaneously, embryonic-axis free cotyledon cultures were established from embryos of various ages. Adventitious shoots developed from cotyledon explants, and the number of multiple shoots formed, increased with time (June-September). Cotyledons extracted periodically from mature fruit stored at 3°C continued to produce multiple shoots in culture, but this gradually decreased with time (15-120 days). After 6 months in cold storage, cotyledon explants failed to develop any shoots.

Open Access