From the Archives: Breeding Better Yellows

Firstly what are better yellows?.Well in my opinion they should have the following characteristics:

  1. Shape. The petals should be wide enough to fill in the space between them thus giving a full flower. The flower should be open, not bell shaped and the end of the petals can recurve somewhat thus enhancing the flattish face of the flower.
  2. The inflorescence should have sufficient numbers of flowers to form a spherical umbel. The flowers should have room to open properly as individuals but should be close enough or overlap somewhat so as to appear as a solid head.
  3. Colour. This obviously will vary, but good deep colour approaching gold is still unknown. Most yellows also fade somewhat as they age, and a good, deep, non-fading yellow would be an achievement. However, light-coloured flowers also should be sought after, with the aim of eventually producing white flowers.
  4. Vigour. This applies to the plant itself, and breeding to produce more vigourous plants is most important. If it takes 5-7 years to flower a number of plants of a cross instead of 3-4 years then progress is only half as fast. Hence vigour, as measured by how long it takes a plant to flower is most important.

My yellow strain originated by sibling crosses of the original orange and yellow cross made by Les Hannibal in California. This original F1 generation (7 siblings) was remarkably uniform and the F1 yellows obtained from it were fairly narrow-petalled and generally bell shaped rather than wide-open flowers. They were also relatively slow growing (although one flowered in four years from seed) and had narrow (4 – 5 cm wide) leaves.

About ten years ago I decided to repeat the F1 cross but used as the orange parent a good-shaped flower produced earlier by crossing an European commercial strain with an Australian selected strain of clivia. The yellow parent used was a yellow which has been vegetatively propagated in Australia for many years. It is self sterile but sets seed freely to other pollen. This new F1 generation has been much more variable than the original, producing some unusual colours and shapes. The plants also have wider leaves and are
better growers. Some flowers and umbels are almost perfect and crossed either with one another or with top quality yellows will obviously produce excellent yellows.

When my first F2 yellows flowered they were pollinated by the Australian yellow which had better shape but still had narrow leaves. Some of these have flowered and are an improvement on the originals. Another yellow strain was produced by Kevin Walters in Toowoomba, Queensland. He obtained pollen from a friends garden from a pale orange clivia which was grown from seed from a Kew Gardens clivia plant, which he used on the self-sterile Australian yellow “Aurea”. When these flowered some had exceptional flowers, large and full with many flowered umbels. They also had broader leaves and are good growers and propagators. Kevin was good enough to allow me to choose half a dozen offsets from his plants to use on my strain of yellow seedlings. Since using their pollen my seeds have obviously been more vigorous, producing more and broader leaves at an earlier stage. In fact, two-year old seedlings are often the size of 3-4 year old plants of the original seedlings.

The European commercial orange strains produce mainly deep orange flowers in a tight head with many buds. Generally, they do not have the open flowers, and spherical umbels that I admire. The plants also tend to be smaller growing to comply with the space problems for cold-sensitive plants in Europe. They also have very wide leaves. However, they occasionally produce a yellow-flowering plant (about 1 in 1000).

From a batch of twenty-thousand seedlings grown in Sydney, an excellent yellow was obtained from about a dozen yellows that occurred. This yellow has already been crossed with selected yellows off my strain. Further yellows that will hopefully in the near future, be incorporated into this strain include yellows bred from “Vico Yellow”. This is a top quality yellow raised from C. x Kewensis. by Sir Peter Smithers. C. x Kewensis is, I believe, simply a select strain of clivia grown (raised?) at Kew Gardens. Sir Peter obtained 2
yellows from a batch of seed, the remainder being orange. “Vico Yellow” has been used in Japan to produce other yellows, and hopefully, these will be crossed with the Australian yellows. In general it has been obvious that each time another strain has been added to the original, it has produced an improvement in vigour.

It can no longer be said that the yellows are more difficult to grow than the orange, and the quality of the blooms is also comparable.The aim for the future is to flower plants in which all the described characteristics are present in one plant and I feel sure that some of the unflowered seedlings will do just that. Then the aim will be to intensify the yellow colour and the production (often via the yellows) of new colours like white, flesh, and pink. At present most of my “improved” F1 plants are being crossed with the very best yellows that are available to me. Although only fifty per cent, roughly, are yellows I feel that these plants will produce more variation both in yellow and non-yellow flowers than in straight yellow x yellow crosses. As some of the “improved” F1 were very pale, it is hoped that crossed with yellow there may be seedlings which are almost yellow but with just touches of orange. If this occurs, such flowers may appear to be much deeper yellows!

As I said in the beginning, this is my opinion as to what better yellows should be. It would be interesting to hear from others whether they agree or not.
Best of Luck to all!
Bill Morris
Clivia News No 2 1993


From the Archives: Colour in Clivia

The colour of a Clivia flower is controlled by the concentration or amount of two different pigments. One is yellow and this pigment is a member of the carotenoid or xanthophyll group (the name carotene comes from the carrot, in which there is a high concentration of carotene giving the orange colour).

The other is red and is a member of the anthocyanin group. This group varies in colour from pink to purple and is responsible for all the colours of flowers except yellow or orange. In the normal clivia flower the orange colour is caused by a mixture of yellow and red pigments. Variations in the orange colour are caused by changes in the concentrations of these two pigments. For example, reddish Clivia are caused by an increased concentration of the red anthrocyanin. If this higher concentration of anthocyanin is accompanied by a lower concentration of carotene then the red colour becomes a truer red (less orange tone). Thus to breed a true red one would have to breed out the yellow – in effect producing a white background instead of a yellow one.

In breeding light coloured orange flowers one has to decrease the concentration of red pigment. This leads to buff or flesh coloured flowers.

Now the concentration of red anthocyanin and yellow carotenoid varies in individual clivias in nature thus giving rise to the natural variation in orange colour observed in different clones of the plant. Selection of different coloured plants and breeding from them can intensify or decrease the colour.

Colour variation produced by mutation

The main mutation or “sport” to occur in Clivia miniata has been the yellow mutant. This has apparently occurred in nature a number of times as a number of different yellows have been collected. This mutation simply involves a failure of the biochemical reactions inside the plant which leads to the formation of the anthocyanin pigment. Without the red pigment, the only pigment present to colour the flower is the yellow carotenoid pigment, thus the flower is yellow. In Clivia plants (as distinct from the flowers) the anthocyanin pigment is also present. However it is only present in sufficient concentration to be seen at the base of the leaves. This is most noticeable in seedlings and young plants where it appears as a purple stain at the base of the leaves. It is purple because the mixing of red and green (chlorophyll) pigments produces purple. If the plant mutates so that it cannot produce anthocyanin then the flower will be yellow and the plant will be plain green without any purple stain.

Just as the orange flowers vary in concentration of the pigments giving rise to different tones of orange, in the total absence of anthocyanin there is still a variation in the concentration of yellow pigments giving rise to a variation in the depth of yellow colour. In other words some yellows are deeper coloured than others. Some are quite light in colour so that some parts of the flower can appear white. Thus a white clivia is simply a yellow mutant (no anthocyanin) in which there is so little yellow pigment that the flower appears white. As it require two chance occurrences in the one plant to produce a white Clivia from a normal orange one, white is much rarer in nature than yellow. However by deliberately crossing two pale yellow plants it should be possible to obtain whites or near whites in one or two generations.

The only other colour variants known at present in Clivia miniata are the so called pink forms. These I suggest come from the very pale orange (buff or flesh coloured) plants. These plants at times have a suggestion of pink in the flower. I believe these are the plants which, as well as a low concentration of anthocyanin, also have a low concentration of carotene. Thus a pink flower is one with low anthocyanin (red diluted to pink) superimposed on a white background instead of a yellow background.

Hence a breeding program for whites could also be used as a breeding program for pinks. This would be accomplished by crossing very pale yellow (or near whites) with pale orange flowers which have pinkish casts. Once really pinkish flowers were obtained then pink crossed with pink could be used to intensify the pink while secondarily further reducing the yellow pigment.

By Bill Morris
Clivia News No 1 1993