I found the following representative images from various sources online.
I'm really quite surprised I haven't found any evidence for a white flowered variation. All it would take is a single mutation to inactivate one of many genes involved in the early steps of the pigment pathway, which should make it a pretty easy variation to arise. Maybe white flowers don't attract whatever pollinates this species and so the trait would rapidly die out after being formed.
The plant family containing this species (Fabaceae) has flowers covering the whole spectrum of flower colors. Reds, blues, yellows, and whites are all common. These colorful relatives suggests there may be the genetic potential for more color diversity within this species, even though they are not yet apparent.
Additional interesting flower color genes can be found in close relatives. If we're very lucky, maybe these related species could cross to L. corniculatus. Improving the floral characteristics of a common weed isn't the sort of project that is going to get much research funding, so there might not be much information available about the possibility of inter-species crosses within the genus. For now, lets just make pretend that we can do these crosses and have a look at what genetics might be available in the genus Lotus.
This dramatically different lifestyle of this species means there would be many non-floral traits that would need to be cleaned up via back-crossing to L. corniculatus if we wanted to maintain the growth form of the original weed. I like the weed's growth habit, so this would be a goal for me.
Some more research into this group reveals there is abundant information about hybridization between species. The reason is that the various species are common forage plants in pasture. Any species impacting agriculture will have a lot of research done on it.
Some of the hybrids I can find information for:
- L. corniculatus x L. tenuis
- L. uliginosus x L. tenuis
- L. corniculatus x L. stepposus
- Lotus corniculatus
- Yellow flower image: sussexwoodland.wordpress.com/category/kingdom-plantae/yellow-wildflower/
- Yellow with red streaks flower image: sussexwoodland.wordpress.com/category/kingdom-plantae/poisonous-plants/
- Orange flower image: www.all-creatures.org/picb/wfshl-birdsfoottrefoil-orange.html
- L. pinnatus
- L. formosissimus
- L. tetragonolobus
- Hybridization in the genus:
- Chromosome counts: