Factors affecting twin-scale propagation of narcissus |
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Authors: | Gordon R Hanks AR Rees |
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Institution: | Glasshouse Crops Research Institute, Littlehampton, West Sussex BN16 3PU Gt.Britain |
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Abstract: | The effects of several factors on bulbil yields obtained by twin-scaling were examined in 4 narcissus cultivars (representing poeticus, trumpet and large-cup types). Bulbils were initiated on twin-scales prepared at any time of year, but grew satisfactorily only if twin-scaling was carried out between June and September. Large twin-scales initiated more bulbils, but smaller twin-scales were also effective propagules and gave high rates of multiplication and bulbils with high relative growth rates. Twin-scales cut from the outer-most scales initiated most bulbils, but more of those bulbils produced from the more central scales were recovered after 1 year; those from intermediate scales produced most and heaviest bulbils after 1 year. Partial loss of the basal plate had no effect on bulbil initiation. Optimum bulbil initiation, emergence and first-year recovery rates occurred following incubation at 15 or 20°C; at 25°C these responses were cultivar-dependent. Bulbil yield after 1 year was greater following incubation for 16 weeks compared with 12 weeks. There was little effect on bulbil yield of cold (9°C) or warm (35°C) treatments of the parent bulbs prior to twin-scaling, except for a marked reduction in the numbers of bulbils initiated when the warm treatment immediately preceded twin-scaling. When the propagules were grown on in a frost-free greenhouse (minimum, 5°C) bulbil yields were higher than from those grown either in a warm glasshouse (minimum, 18°C) or in the open; an initial cold period (5°C) given before the propagules were placed in the frost-free house also reduced yield. |
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