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Factors affecting micropropagation efficiency of 32 selections of Rubus, including the pre-treatment and initiation culture stages, were investigated. Chilling at 4°C for 6 weeks as a pre-treatment significantly promoted in vitro initiation culture; up to 65% of initiation cultures post chilling were successful. The cytokinin 6-benzyladenine (BA) was the most effective of the three tested for promotion of multiple shoot development in culture, with an average of three to seven shoots or plantlets developed from each single node. Alternating the concentration of BA between 4.44 and 13.31 lM from sub-culture to subculture improved recalcitrant Rubus micropropagation, and reduced the problems associated with long-term culture in the presence of high concentrations of BA. Reduction of the strength of macro-and micro-elements in the basal medium from half to one-third, with addition of 0.49 lM indole-3-butyric acid and 0.05% activated charcoal, and placing the cultures under reduced light intensity (17 lmol m -2 s -1 ), was found to alleviate chlorosis and improve micropropagation with high quality Rubus plantlets. Response to in vitro culture differed greatly and consequently different methods of micropropagation were required by different genotypes. From these selections, three types of micropropagation including micro-cutting, micro-shoots and multi-shoots were observed, and their efficiency was characterized.

Protoplast fusion has been used to produce novel allotetraploid hybrids for use as parents in crosses with diploids to produce easy-peel, seedless, triploid citrus cultivars. Forty three plants were produced from fusions between protoplasts of 'Encore' mandarin and 'Valencia' sweet orange, and of 'Encore' and 'Caffin' clementine mandarin in which protoplasts of each of the donors were isolated from embryogenic callus. Forty plants were confirmed as tetraploid by flow cytometry and chromosome counting. Three (less than 10% of all regenerants) were non-hybrid diploids. DNA fingerprinting confirmed that both parents contributed DNA to the hybrids, which were therefore allotetraploid. The hybrids showed morphological features typical of other tetraploid citrus, including broad, thick, dark green leaves. However, they grew much faster than colchicine-induced autotetraploids. The allotetraploid hybrids will be used in crosses with the diploid cultivar 'Encore' mandarin and other clementine-type mandarins in an effort to generate seedless, triploid, easy-peel cultivars with 'Encore-type' flavor.

A seasonal analysis of cytokinin activity in Sargassum heterophyllum (Turn.) J. Ag. was undertaken. The data thus obtained show that there are pronounced quantitative and qualitative seasonal changes in the cytokinin content of the holdfast, vegetative and reproductive laterals. These changes correspond with the seasonal periodicity of growth, development and reproduction of this alga. Three major peaks of activity were detected: a polar peak, which co-chromatographed with glucosylzeatin, and two non-polar peaks which had the same Chromatographie properties äs zeatin and ribosylzeatin, and äs isopentenyladenosine and isopentenyladenine, respectively.

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