BREEDING FOR TETRAPLOID RED PHALAENOPSIS

Story and photos by A. Dean Stock, Ph.D.

This article is first published in IPA Journal - Phalaenopsis - Foruth Quarter 2005 issue.  Made available online with permission from the author.

BREEDING FOR TETRAPLOID RED PHALAENOPSIS – A. Dean Stock, Ph.D.

Diploids, triploids and tetraploids – why breed for tetraploid reds? For clarification: “n” equals 19, which is the number of chromosomes in either the pollen or the ovule of a normal diploid phalaenopsis. In a full set of genetic material, consisting of paired chromosomes, there will be 2n or 38 chromosomes. In a triploid plant, there are 3n or 57 chromosomes, in a tetraploid, there are 4n or 76 chromosomes, and in an aneuploid, which results from breeding a diploid or a tetraploid with a triploid, there are an abnormal or odd number of chromosomes.

The major reasons for breeding towards tetraploid red phalaenopsis is to increase flower size and to obtain a more standard phal shape. Increased flower count and better presentation are additional breeding goals.

Phal Chingruey's Blood Red Sun 'Ching Ruey'	Phal Ching Hers Goddess 'Lin'	Phal Brother Passion 'Patricia'
Phal Brother Precious Stones 'Patricia'	Phal Strawberry Wine 'Patricia'	Phal Brother Sally Taylor 'Patricia'

Almost all of U.S. breeding has been with diploids, triploids, and the aneuploids that have resulted from breeding triploid reds to diploids and tetraploids. Aneuploids were also produced through attempts to increase flower size by breeding triploid reds to tetraploid pinks and stripes.

Diploid red breeding has reached a high level of quality and as we have seen with Eric Goo’s work, is well worth pursuing. However, great care must be taken to mate diploids to diploids. The use of plants such as Phal Cordova, Golden Buddha or Spirit House leads to problems. Most attempts to increase size and flower count with diploid red breeding lines has resulted in the production of triploids. Unfortunately, triploid phalaenopsis will often produce seed, and the results of using “anything that will breed,” has produced a sea of aneuploids, which are then used in further breeding attempts. The outcome of this type of breeding is the well-known ‘sterility barrier’ so common in today’s phalaenopsis breeding.

To give perspective to the problem, consider that a phalaenopsis breeder with the knowledge and experience of Carlos Fighetti observed in his recent article in the Phalaenopsis Journal that with the matching of Phal Golden Buddha with Zuma Garnet, the first of the “new” red phals was produced. More specifically, the near-tetraploid aneuploid Phal Golden Buddha was crossed with the diploid Zuma Garnet to produce the aneuploid plants registered as Phalaenopsis Cordova. Based on what we know about chromosomes and their relationship to plant sterility, Phalaenopsis Cordova should never be used for breeding. Crosses of this nature produce dead ends.

The degree to which triploid and aneuploid plants have been used in breeding for red – and yellows – is such that it is amazing that any fertile plants can be found. All of this type of breeding should be avoided if one wants to achieve good-sized red phalaenopsis with other desirable traits and with fertility the expected norm instead of a rarity. Instead, breeders must rely on chance tetraploids such as Paifang’s Queen ‘Brother’ and Taipei’s Gold ‘Gold Star’ or documented colchicine-converted diploids. All chance tetraploids must be documented by accurate chromosome counting. One additional important concept here is that converting triploids to hexaploids through colchicine treatment does not produce good breeding plants because hexaploids do not produce stable, even ploidy in their offspring.

Why consider yellow flowers in red breeding? There is no true red phalaenopsis in nature. So we create red by combining pigments. Without strong yellow pigment, you do not obtain strong red color. You need to produce good tetraploid yellows in order to mate them with tetraploid dark pinks or lavenders. Where do we get good tetraploid yellows?

The stage was set by the use of one of those pesky triploid plants, Phal Golden Sands ‘Canary.’ Golden Sands ‘Canary’ was out of a cross of a large white and Phalaenopsis fasciata. The cross produced a lot of good-looking triploid yellows, but the clone ‘Canary’ had the best color. Several years of breeding attempts yielded nothing, and the plant was thought to be sterile. Later, several species were bred to this plant, and these crosses have produced many outstanding yellows: Liu Tuen-Shen (Golden Sands x gigantea); Golden Amboin (Golden Sands x amboinensis); Goldiana (Golden Sands x lueddemanniana); and more recently Golden Bells (Golden Sands x venosa).

Golden Amboin and Liu Tuen-Shen have both been very important on the way to reds, but Golden Bells will also prove to be very important in the future. These plants are of great importance because they are good tetraploid yellows with strong color, good size and shape, and relatively high flower count.

Why are they tetraploids? It turns out Golden Sands ‘Canary’ is a rare plant that gave up trying to split three chromosome sets, and lumped everything together into a 3n ovule. It does not produce viable pollen. So, when matched with pollen (n) from a diploid species, tetraploids (4n) resulted, and the stage was set for producing good, tetraploid yellows and reds. Another modern tetraploid yellow, Taipei Gold ‘Gold Star’, was a chance tetraploid in an otherwise triploid grex. This plant will also continue to play a part in the development of large red phalaenopsis.

Now it seemed all we needed was a good source of dark pinks or lavenders. But crossing tetraploid yellows to tetraploid pinks produced sunset colors, so this line of breeding was not pursued in the search for clear reds. With time, and line breeding, this approach would have succeeded, and you will see more of this type of breeding in the future.

In Taiwan, the crossing of a large white, P. Mount Kaala, with P. pulchra produced an array of triploid plants with pink to lavender blotches and spots. One of the plants produced had darker color but poor form. It probably would not have been used for breeding in this country. A very observant breeder in Taiwan, however, tried the plant and found it to be fertile. This plant would be known as Paifang’s Queen ‘Brother’, a rare chance-tetraploid resulting from an unreduced 2n pollen cell from the P, pulchra.

Brother Orchids used this plant for breeding, and over time, found that by matching it to plants such as Liu Tuen-Shen and Golden Amboin heavily pigmented, fertile flowers were produced. Subsequent line breeding by Brother Orchids and others has resulted in a wide selection of heavily spotted and solid red flowers with good fertility and a size ranging from 7cm to about 9cm. To obtain larger sized flowers, we must now concentrate on breeding this wealth of material to large, dark pinks to produce the final result – 10cm reds. Some of this breeding is already accomplished with crosses such as Brother Cortez Red showing the way. We are within a generation or two of our goal. The plants now available allow any serious breeder to produce a line of large, free-breeding, red phals. Some of those commonly available that can be used to produce good tetraploid reds follow. But beware of crosses such as Sogo Cock and Sogo Rose. Despite their awards and visual appeal, these plants are also aneuploids.

A. Dean Stock is a founding member of IPA, a retired Cytogeneticist/Medical Geneticist/Cancer Researcher, and owns Canyon Orchids in Kanab, Utah.