Many years ago when Wendy started growing daffodils I remember reading several articles which suggested that when making a cross between two cultivars, the choice of which to use as the seed parent and which as the pollen parent was highly significant. Using cultivar A instead of B as the seed parent would guarantee for example a much greater number of progeny which were of Division 1 proportions than if it was used as the pollen parent. Later I listened to (and read) Peter Brandham decrying this and saying that it made no difference since in both ways half the chromosomes from each of the parents were present in the progeny irrespective of the choice of seed parent. However can anyone explain the following, or perhaps direct me to the source of a written explanation.
For the past five years I have been crossing narcissus species to get miniature cultivars. I keep detailed records of when the seed emerges and then in subsequent years the date when the shoots emerge through the soil. All the crosses are grown in an unheated greenhouse. In 2014 I made a number of crosses between a very vigorous Narcissus bulbocodium which I had found at Baragem de Santa Luzia and Narcissus lusitanicus also from Portugal. The crosses were made both ways on the same day. The seeds were planted in identical pots, in the same mix of compost and have been grown in the same bed in the greenhouse. The three pots of seed with Narcissus bulbocodium as the seed parent started to germinate on the seventh, tenth and fourteenth of November (remarkably consistent). Two pots of selfed Narcissus bulbocodium germinated on the fourth and twelfth of that month. Two months later there is no sign yet of germination of the two pots where Narcissus lusitanicus was the seed parent. I am not particularly concerned since none of my triandrus crosses have yet germinated, though Narcissus lusitanicus is a very early flowerer and flowering size bulbs are almost ready to burst their buds.
Question? If as Peter Brandham alleges there is no difference between the progeny whatever the seed parent, what is the mechanism that allows the seed to remember which was the seed parent? Will the two different progenies flower at the same time?
James,it has always seemed to me that the difference between real botanists and just plain gardeners is that the botanists write things down!!!
Peter Brandham was saying that he had never observed differences. But your careful records indicate that there is something there worth keeping an eye on.
Loyce McKenzie
To be fair to Peter, Loyce, his comments on the subject were also made many years ago and research has moved on. He has always been very helpful and patient in his response to my questions.
I posted the same question on the SRGC forum and have now received a response pointing me to an article at
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC535866//
It is now clear that what I have observed is a parent-of-origin effect.
Cytoplasmic DNA comes from the mother so I assume that a good rule of thumb is to use the more vigorous plant as seed parent. In species crosses this can be a matter of practicality – it is easier to use jonquilla as a seed parent than triandrus because it is easier to grow. Interestingly, one of my best hybrids of this type has triandrus as the seed parent.
I expect it is too soon to draw conclusions about the bulbocodium triandrus cross but it is possible for A x B and B x A to be distinguishable, in principle at least.
The most obvious possibility is that the germinated bulbocodium x triandrus seed is not true to cross.
It strikes me that seed produced by a bulbocodium may be encased and structured differently and hence physically able to sprout earlier. This wouldn’t necessarily mean that as bulbs they will sprout earlier.
“The most obvious possibility is that the germinated bulbocodium x triandrus seed is not true to cross.”
Yes that was my first thought and one of the problems of starting hybridisation so late in life is whether I will live long enough to see the flowering results. However I may get some guidance in examining the leaves when the shoots come through next year. I will have the selfed bulbocodium seedlings to compare them with.