The germination of raspberry seeds was favoured by applying certain combina tions of chemical pretreatment before giving up to six weeks of moist-chilling before sowing, by adding 500 p.p.m. gibberellic acid just before sowing, and by providing supplementary light after sowing. The most useful chemical pretreat ment was 20 minutes with concentrated sulphuric acid followed by six days with 10 per cent calcium hypochlorite containing an excess of calcium hydroxide. For some seed samples such pretreatment eliminated the need for a subsequent period of moist-chilling, but for others a six-week period of moist-chilling was still required. Pretreatment with higher concentrations than 10 per cent of cal cium hypochlorite, 0-5 per cent of sodium hypochlorite, or 1 o per cent of thiourea, or pretreatment with the stated concentrations of these chemicals but in each case without the addition of calcium hydroxide, frequently delayed or prevented germination. The results of these studies are in accord with the hypothesis that the germination capacity of raspberry seeds is determined by interactions between growth inhibitors and promoters. Such substances have been detected in black berry seeds and it is suggested that a similar situation exists in seeds of the rasp berry.

Studies on Factors which promote Germination of Raspberry Seeds

A STUDY of the chromosomes of Rubus was undertaken at the request of Dr. L. H. Bailey of the Bailey Hortorium of the New York State College of Agriculture, Cornell University at Ithaca. In a preliminary report (Einset, 1947) the cytological methods were outlined and data were presented on chromosome number, morphology and behavior in a number of forms. Specific determinations were made by Dr. Bailey; specimens of the plants studied were deposited in the herbarium of the Bailey Hortorium and living plants were established in a planting at the New York State Agricultural Experiment Station at Geneva.

Apomixis in american polyploid blackberries

Brambles (a general term used to describe raspberries and blackberries in the Rubus genus) are an extremely variable group of plants found in temperate zones around the world. For thousands of years, man has collected bramble fruits from native stands. However, since the 1800s, considerable attention has been given to use of brambles as a cultivated fruit crop. Bailey (1923, 1925, 1932) described hundreds of species of Rubus in North America alone; many of these are now considered to be hybrids. With a ploidy range of 2x to 12x (x = 7) numerous forms are certainly possible. Adding other factors such as ecotypes and apomixis complicates efforts to categorize brambles. Recent attempts to classify this variable genus have not resolved the taxonomic jumble. Bailey (Hortorium 1976) lists many cultivated species and varieties of brambles, summarized in Table 1.

Brambles (Rubus spp.)

approved: . _ . . Barbara M. Reed An in vitro regeneration system was developed for leaf explants of Rubus cultivars. Adventitious shoots were successfully produced on thirteen economically important cultivars with varying ploidy levels: Cherokee (4X), Chester (4X), Hull Thomless (4X), Kotata (7X), Marion (6X), Navaho (4X), Shawnee (4X), Thomless Evergreen (4X), and Waldo (6X) blackberries and Autumn Bliss (2X), Heritage (2X), Latham (2X), and Watson (RubyTM) (2X) raspberries. In-vitro cultured plantlets were pretreated with 1 ^M thidiazuron (TDZ) on NCGR-RUB medium for three weeks. The top four to six young leaves with petioles removed were placed on regeneration medium (RM) with indole-3butyric acid (IBA) and either N^-benzyladenine (BA) or TDZ for one week in the dark followed by 16-hour light. RM without IBA induced a significantly higher percentage of regeneration, more shoots per explant, and less callus compared to 0.5 pM IBA BA (10 MM) was more effective than TDZ for leaf regeneration in vitro from most Rubus cultivars. The addition of the iron chelate, sequestrene, to the second RM increased regeneration of heptaploid 'Kotata' and hexaploid 'Marion' by 60%. Agar, Gelrite, and agar-Gelrite combined had no significant effects on regeneration of 'Kotata', 'Marion', and 'Navaho' blackberries. Silver nitrate (AgNOs) did not influence shoot regeneration for four blackberry cultivars, but when included in the first RM significantly reduced callus formation. In vitro shoot regeneration ofRubus is highly genotype dependent, but berry type and ploidy level of 13 cultivars we screened did not influence the process. Virus infected plants are often symptomless and explant sources used for tissue culture research are rarely tested for viruses. Single and multiple virus infected greenhousegrown plants were graft-inoculated and maintained as virus stock cultures. Raspberry bushy dwarf virus (RBDV), tomato ringspot virus (TomRS V), and tobacco streak virus (TSV) infected in vitro 'Mailing Landmark' raspberry cultures were tested for multiplication and growth. Virus status was determined by enzyme-linked immunosorbent assay (ELISA) and bioassay, and reconfirmed before and after multiplication tests. No symptoms were observed on greenhouse stock plants except one with three-virus infection (RBDV + TomRSV + TSV) which was stunted and had yellow leaves. In vitro multiplication of plantlets with multi-virus infections (2and 3-virus combinations) was significantly reduced. No obvious differences were displayed for in vitro shoot height and morphology. We recommend using virus-free plantlets for in vitro experiments. ©Copyright by Chih-wei V. Tsao April 27, 1999 All Rights Reserved RUBUS LEAF REGENERATION AND MICROPROPAGATION OF VIRUS INFECTED RASPBERRY

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Rubus leaf regeneration and micropropagation of virus infected raspberry

We categorized the dormancy and germination of blackberry (Rubus glaucus Benth) seeds from the Germplasm Bank System for Food and Agriculture of the Colombian Nation. A tetrazolium test showed normal seedling production viability, but seed coat impermeability prevented imbibition, which is considered an expression of exogenous dormancy; however, this was released by immersing the seeds in 5.25% sodium hypochlorite for 16 to 21 hours. The treatment was applied to 10 accessions of Castilla blackberry, harvested during the dry and rainy seasons. The seeds were germinated under light and dark conditions. The highest germination counts were obtained with the dry-season-collected seeds incubated in darkness and with the rainy-season seeds incubated under light conditions. Differential germination responses were also independently determined by genotype, incubation conditions (light or darkness) and collecting season.

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G. L. Slate

Papers

Treatment of blackberry seed to secure first year germination.