Genetics & breeding

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 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. 

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):

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!

Ploidy