Genetics & breeding

Snowdrop genetics is not a topic much is known about. Galanthophiles from the past have however discovered the pattern of inheritance of some snowdrop traits.

A brief explanation

Genes are a sequence letters written on the DNA. Each sequence contains instructions for a specific quality, like for example flower colour in snowdrops. Every gene occurs in two copies (alleles) in most snowdrop species and varieties (1). These snowdrops have a diploid genome.

Genetics and inheritance of traits in snowdrops
As the genes of snowdrops occur in two copies (alleles), the resultant snowdrop of a cross is determined by which copy (allele) of each gene it inherits from the parent snowdrops. Some alleles are dominant, which means that just one allele will cause a specific characteristic to appear. One example of this is the inverse poculiform appearance of cultivar ‘Trym’. If Trym passes on the inverse poculiform allele to a seedling, this seedling will have the inverse pociliform appearance. This happens even if the other parent of the seedling will pass on the allele of a normal flower. The gene is said to be dominant.

‘Trumps’, a seedling of snowdrop variety ‘Trym’ with the dominant inverse poculiform flower allele.

Another type of allele is the recessive allele. An example of this in snowdrops is the gene for yellow flowers. In this case, if a parent yellow snowdrop passes on the gene for yellow flowers and the other parent is a green snowdrop that passes on the gene for green flowers, the resultant seedling will be green. The green gene allele will determine the flowering colour of the flower over the yellow gene allele, meaning the yellow gene is recessive.

Wendy’s Gold’, a snowdrop with two recessive yellow flower alleles.

An interesting case in snowdrop appears to be the gene for double flowers. The gene for double flowers in flore pleno appears to normally be recessive. By luck, Joe Sharman has however found a dominant gene for double flowers (2). This allows him to force the double flower characteristic in snowdrops more easily with his crosses.

The example of ‘Golden Fleece’
So let us now consider the cultivar ‘Golden Fleece’. It has genes for inverse poculiform flowers, as well as those for yellow flowers.
As mentioned, the gene for inverse poculiform flowers is dominant. If we write a dominant copy (allele) of an inverse poculiform flower as A and a recessive copy for a normal flower as a, it will have either AA alleles or Aa alleles.

The gene for yellow flowers if recessive. If we describe a dominant allele for a green flower as B and a recessive copy for a yellow flower as b, it will have bb alleles.

‘Golden Fleece’, a plant combining the dominant ‘inverse poculiform’ flower shape allele with two recessive yellow flower colour alleles. 

How to get there?

Joe Sharman crossed variety ‘Wendy’s Gold’ with normal yellow flowers (aa, bb alleles) with variety ‘Trym’ with inverse poculiform green flowers (AA, BB alleles or Aa, BB alleles) (3). (We can assume that the gene for yellow flowers is quite rare.) We can actually determine what the next generation will look like. For this example we will go for AA, BB alleles for ‘Trym’, yielding in the first generation (F1):

  From Wendy’s Gold: ab From Wendy’s Gold: ab
From Trym: AB AaBb: inverse poculiform, green in F1 AaBb: inverse poculiform, green in F1
From Trym: AB AaBb: inverse poculiform, green in F1 AaBb: inverse poculiform, green in F1
Joe Sharman actually managed to grow two seedlings from this cross, yielding two green, inverse poculiform flowers in the F1 population after five years. This means both will have the alleles AaBb. No yellow flowers yet, but one more cross with yellow flowers should get him there. He crossed these plants once again with another G. plicatus plant with normal yellow flowers, yielding in the second generation (F2):
  From yellow plicatus: ab From yellow plicatus: ab
From the new seedling: AB AaBb: inverse poculiform, green in F2 AaBb: inverse poculiform, green in F2
From the new seedling: Ab Aabb: inverse poculiform, yellow in F2 Aabb: inverse poculiform, yellow in F2
From the new seedling: aB aaBb: normal, green in F2 aaBb: normal, green in F2
From the new seedling: ab aabb: normal, yellow in F2 aabb: normal, yellow in F2

So normal green, normal yellow, inverse poculiform green and inverse poculiform yellow flowers should all occur with equal chance. Although Joe Sharman did indeed find all types of snowdrops, there was only one ‘Golden Fleece’ (2). Although luck was not entirely on his side, he had done the breeding work properly!

Overview of traits and expected pattern of inheritance:
Flower Type Inheritance pattern
Inverse poculiform flowers Dominant
Yellow coloured flowers Recessive
Double flowers Recessive, but in rare cases dominant
Poculiform (4) Recessive
Green ovary, yellow inner mark (e.g. ‘Blonde Inge’, ‘Midas’) (4) Dominant (based on hearsay)
Hopefully more breeders can use this knowledge of breeding to develop more interesting varieties.

Ploidy

Interestingly, Martin Baxendale has attempted to breed tetraploid snowdrops (5). These plants would contain four copies of each gene. Triploid snowdrop varieties, i.e. varieties with three copies per gene, are known and tend to be more vigorous. ‘John Gray’, ‘Bertram Anderson’, ‘S. Arnott’, ‘Magnet’, ‘Ginns’, ‘Imperati’, ‘Straffan’, ‘Imbolc’, ‘Faringdon Double’, ‘Viradapice’ and ‘Warei’ are all regarded to be triploid. ‘Mrs Macnamara’ might even be tetraploid. Due to problems during meiosis (simply put: the process of making eggs and seeds for reproduction by halving the DNA), these triploid plants are not particularly fertile. Tetraploid plants would still be vigorous, but also be more fertile, allowing plant breeders to grow and breed more good snowdrop varieties.
1. B. J. M. Zonneveld, J. M. Grimshaw and A. P. Davis. The systematic value of nuclear DNA content in Galanthus.
Plant Systematics and Evolution. Vol. 241, No. 1/2 (October 2003), pp. 89-102
2. Simon Garbutt. Joe Sharman’s snowdrop breeding. Daffodils, snowdrops and tulips yearbook 2017 page 44-47.
3. Val Bourne. Hot on the trail of those elusive snowdrops. 2017 Telegraph.
4. Dimé Troux. Inheritance patterns of Galanthus facebook post. 2019
5. Martin Baxendale. Breeding new snowdrop cultivars. Daffodils, snowdrops and tulips yearbook 2008 page 56-60.
Last updated bySiopaos
298 reads
How did you like this article?0020

Leave a Reply

Your e-mail address will not be published. Required fields are marked *