daylily hybridization

daylily hybrid
daylily hybrid
daylily hybrid

DIPLOID DAYLILY GENETICS

Diploid daylilies are subject to the classical, Mendelian rules of genetics. Let's suppose, for instance, that in daylilies, the color yellow is produced by a single enzyme encoded by a gene abbreviated by the symbol Y. Now suppose a daylily whose gene for the yellow color producing enzyme is mutated, in such a way that the enzyme is unable to produce the color, causing the flowers to remain white. We will refer to this mutant, non-functional version of the gene as y.

The convention for genetic nomenclature is for the normal functional version of any gene to be capitalized, and recessive, mutant versions to be lowercase. Since there are different possible non-functional mutations, these are usually distinguished with superscript, like this: ywhite, or ycream for example. It does get more complicated! For instance, there are dominant mutants as well. If a mutant yellow producing enzyme starts producing orange, and such a mutation is expected to be dominant, it would be noted thusly: Yorange. But for the purposes of daylily breeding, we can afford to keep things simple.

Let's begin with two daylilies, one yellow that got a normal copy of the Y gene from the pod and the pollen parent, whose genotype will be denoted by YY, each Y representing an individual copy of the gene in the plant. These individual copies are called "alleles." The other daylily is white, ywhiteywhite. I'm sure you've all seen this table before:

Y Y
ywhite Y ywhite Y ywhite
ywhite Y ywhite Y ywhite

None of that progeny looks white, all of it is phenotypically (its appearance) yellow, but it is genotypically (the underlying genes) heterozygous (different alleles of the genes) for the yellow gene and all of them carry one copy of the mutant gene that is unable to produce the yellow color.

DAYLILY SIBLING CROSS

Sibling crosses are very useful to uncover the "hidden" mutant, recessive gene for white in this example.

This is a table for a sibling cross from the cross made above:

Y ywhite
Y Y Y Y ywhite
ywhite Y ywhite ywhite ywhite

On average, one daylily out of four will have two functional alleles of the gene that encodes for the yellow producing enzyme. In some cases this means the color will be more vivid than the flowers with only one copy of the functional enzyme and one copy of the non-functional mutant enzyme, which could appear as pastel yellow depending on the biochemical pathway that underlies color production. One daylily out of four will be white.

Since we crossed a yellow flower to a white flower to begin with, are we just back to square one, have we wasted our time? No! This is an example with ONE gene, but thousands more are similarly mixed and matched in every cross. Perhaps the white flowered plant had genes for very large blooms, and the yellow flowered plant had genes for extreme vigor. Perhaps you are looking to create an extremely vigorous plant with very large pastel yellow flowers!

DAYLILY BACKCROSS

A backcross means crossing one of the progeny back to the parents. This strategy is usefull if one parent already possesses most of the desired traits, and one specific feature needs to be introduced to the mix.

E-mail Chantal.