|Gentian Breeding at Tynebank|
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A progress Report By Ian McNaughton
There are already too many cultivars of autumn gentians, numerous mediocre seedlings have been given names over the years. Many of the older cultivars are late flowering and have untidy growth habits, with long trailing shoots bearing single flowers. Some are not easy to grow and lack permanence in the garden. Some are difficult to tell apart, undistinguished and indistinguishable. In spite of good progress by other breeders, there remains scope for further improvement, the challenge is there.
The breeding and selection programme at Tynebank was started some years ago, aimed at the following criteria: early flowering and floriferousness, of which multi-headedness is a factor, flower size, confirmation, and marking of the corolla, striping and spotting. Vegetative characters are important and selection of compact types, both tufted and low spreading, has been another objective. It is desirable for selling that a plant should "look good in a pot", this is also important of course, for showing. Good tillering and rooting ability for ease of propagation is beneficial to both gardener and nurseryman. Vigour and persistence in the garden are other obvious aims. At first, the strategy involved deliberate hand pollination of parents selected for specific characters, for example aiming to combine good flower colour of one parent with early flowering of another. Crosses were carried out in the glasshouse using pot grown plants. Flowers were emasculated before pollination and then covered.
With very few exceptions, results were unpromising, although many hundreds of seedlings were raised to flowering size and a number retained for several years for further assessment.
Several difficulties have been encountered, one in that seed formation may be inhibited by surrounding petal and sepal debris, causing capsules to rot before seed has had time to ripen. Debris must be carefully removed, this is time-consuming. The problem is made worse by the cold, wet conditions normally prevailing in a Scottish autumn. Many plants were killed in the very severe winter of 1994/95. Gentians do not take kindly to water-logged pots which are then frozen for weeks on end, plants eventually succumbing to root rot. Hybrids as well as a collection of cultivars, assembled as possible parents, suffered high losses. This proved not to be a setback, however, but a blessing in disguise as much mediocre material was cleared out, it was followed by re-thinking and a virtually new start. A more pragmatic system of breeding was started in l995 based on an elite population of carefully selected plants, placed in spatial isolation, as far as was practicable, from other gentians. As pollination is carried out mainly by hover flies, rather than bees, the isolation distance may not have to be far. Seed was harvested from each plant separately, pollen parent(s) being unknown. Vernalization is necessary to induce germination and seed was sown in early January. Germination is usually erratic and seedlings emerge over several weeks. They are ready to be pricked out in April/May, currently into 3 cm. plugs. An effort was made not to neglect the smaller seedlings, but also to earmark the most vigorous ones.
Two promising Tynebank seedlings were named in l996, but these were superseded and discarded before reaching the commercial stage, at least a sign of progress! It was not until l998 that the programme began to show real promise when a particularly good batch of seedlings flowered for the first time. These were derived from the second cycle of the "elite population" breeding, roughly equivalent to an F2 generation. Several were outstanding for various reasons. White flowered seedlings crop up from time to time, most have been forgettable but two with large white flowers and vigorous foliage were of particular interest. One has plicae with pale blue speckling, the other is a good pure white (this is quite rare). These show promise of being far superior to the old forms; Gentiana sino-ornata "Alba" and "Mary Lyle". Both have been cloned for further evaluation. Numerous deep, vivid blue flowered plants of good constitution have been raised, they include very compact, tufted types. The best of these must be compared to cultivars recently produced by other breeders, e.g. the multi-awarded "Shot Silk" from Aberconwy Nursery, to which it must be said many are related. Other compact types have entirely different origins, some complex, e.g. from triple-crosses. One vigorous seedling with large deep blue flowers seemed distinctive and has been named "K2" earlier this year. Several seedlings have occurred with distinctive forked, white markings contrasting with dark blue. These resemble "Edith Sarah". One, in particular, has better floral markings and is compact, yet vigorous. The vigour of "Edith Sarah" is said to be declining, possibly due to continual vegetative propagation, a replacement is surely due. One vigorous, multi-headed seedling produced flowers early and of a very deep, vivid irridescent blue, outstanding and the best I have seen. It is fertile and several seedlings from it are being raised. The parent plant shows promise of consistent early flowering, coloured buds at present means that it should flower before mid-August. There are many compact seedlings of diverse origins, both tufted (hedgehog) and low spreading forms. It is possible that the high percentage of compact plants is due to perseverance with the smallest seedlings, but I have no evidence of a correlation. One aim is to produce small growing forms suitable for growing in troughs. This season should tell if this objective has been achieved, there are several candidates. Big differences in general growth habit, leaf form and colour are in evidence, this variation is interesting in itself, even before any flowering.
Growth and health of all gentians is excellent this year, particularly of those grown in pots which range in size between 1L. (13 cm diam.) and 10L. (28 cm diam.). One plant has just been found to have several shoots with variegated leaves, it remains to be seen what the flowers are like. Shoots are currently being rooted. Another problem has been that the numbers of parents contributing to seed production may be restricted because of sterility of certain genotypes. Not all streams flow into the gene pool. A good example of this is G. x carolii, potentially a useful parent due to it's consistent early flowering. Many hand-pollinations using G. x carolii failed and, in my experience, it never sets seed in the garden. Reasons for sterility are not known. Scientific breeding of the autumn gentians is hindered by a general lack of knowledge of chromosome numbers, genetics, breeding systems and floral mechanisms. Previous experience has shown that a particular clone (cultivar or hybrid) may flower early one season but would not necessarily do so the following year. Consistent early flowering requires to be demonstrated over several seasons. It seems there are environmental as well as genetic effects on flowering time. There is cause for optimism as some previous selections are already in bud at the time of writing, July 20th. Big differences in over-wintering ability in a normal season have been observed in seedlings raised from female parents of different origin. One source in particular produced plants with a very poor rate of survival in their second winter, another source was good in this respect.
Club members with a special interest in gentians will be welcome at Tynebank at any time, but by prior arrangement please (Tel No. 01875 340797).
The Nursery at Berrybank nearby is open between 1030 and 1700 hrs daily, there are alpines, herbaceous plants, ferns etc. for sale as well as a good range of gentians.
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