I've been working on producing a hybrid swarm of sorts of sunflowers combining genetics from annual sunflower as well as various perennial species. I've been learning a lot.
I know that there are a fair number of people who have been interested in hybridizing Jerusalem artichoke (
Helianthus tuberosus) with annual sunflower (
H. annuus) in hopes of producing tuber crops with improved diversity of traits to select from. Note: this hybrid produces tetraploid individuals which would be intercompatible with eachother for future crosses, but would result in sterile triploids and pentaploids if back-crossed with either the
H. annuus or
H. tuberosus parent respectively.
The primary challenge holding most people back is getting bloom overlap between the annual sunflowers and the Jerusalem artichoke. Based on my experiences so far a number of people are on the right track by attempting to use early blooming selections of Jerusalem artichoke for this cross. However, it is also helpful to simply plant your annual sunflower seed late (and in pots). The combination of planting them late as well as growing them in pots results in plants which are significantly smaller and portable with a later bloom time. This means you can easily reach the flower heads for hand pollination even if using genetically large selections of annual sunflower. Additionally, many wild forms of annual sunflower naturally bloom later than the cultivated types on account of not having had intense selective pressure for agricultural purposes. If you don't care much about large flower or seed size in the annual parent it can be a very good option to use these wild types which not only naturally bloom later, but also typically have branching with multiple flower heads which results in an extended bloom time. If you are using a single headed variety of annual sunflower and find it is beginning to initiate flower heads too far in advance of your H. tuberosus, you can actually initiate secondary flower heads which will bloom later by pinching the terminal flower bud while it is still small. The resulting secondary blooms will be smaller and possibly deformed, but they will still contain the correct genetic material needed for producing the desired hybrids.
When making this cross it is important to use the
H. tuberosus parent as the seed parent and the
H. annuus parent as the pollen parent. Two reasons for this.
- Many cultivated forms of H. annuus have some degree of ability to self pollenate which means that it would be difficult to prevent self pollination. The perennial H. tuberosus is generally self incompatible and really very resistant to seed set overall so when it is used as the seed parent seed set will be low, but the seeds which are produced can be expected to be 100% hybrids as long as only one H. tuberosus clone is in bloom at a time to prevent accidental cross pollination between different clones of the same species.
- H. tuberosus as the seed parent is fairly receptive to receiving pollen from H. annuus to produce seed whereas H. annuus typically is not receptive of pollen from H. tuberosus. Using H. annuus as the seed parent would generally result in little to no hybrid seed being set as well as a huge waste of time growing out seedlings only to find no hybrid offspring.
Things can get way more complicated than this when you begin to dig deeper and the tetraploid nature of this hybrid will make it harder to select for morphological traits that you wish to pursue compared to diploid annual sunflowers on account of the higher ploidy meaning there are multiple genes competing for expression of any given trait. That said, this hybrid should still be far easier to use for breeding and selecting than pure
H. tuberosus which are hexaploid as four competing genes for each trait is still simpler than six competing genes for each trait!
Below is a link to the progress I've made so far with my
Helianthus breeding work (I'm not limiting myself to just these two species). I update this blog post regularly as I gain additional information or observations to share.
https://johannsgarden.blogspot.com/2021/08/perennial-helianthus-breeding.html
