In previous posts I talked about creating and identifying polyploids, and was asked for an update on the experiment. Sadly, the putative tetraploid (I say putative because it’s not confirmed until the chromosomes are counted) Passiflora edulis ‘Sweetheart’ seedling with curly leaves succumbed to an unknown disease. I hadn’t made cuttings of it because I was waiting for it to grow larger. It happens.
However, I did have a different plant flower: a P. edulis x P. incarnata F1 cross, which was treated with oryzalin in 2013. I didn’t have any other tetraploids flowering, so I was unable to use its pollen or have it set fruit. The flower also displayed some abnormalities: some of the petals didn’t separate, and some of the anthers were fused. It should begin blooming again shortly so I will try again then.
My P. caerulea tetraploid conversion is yet to flower, but it is much larger than in previous posts. P. caerulea tends to be slow to flower for me; I have some seedlings which are three to four years old and have still not even thought about blooming.
I have some other Passiflora series dysosmia (Dysosmia includes Passiflora foetida and the ones like it, i.e. P. arida, P. sublanceolata, P. urbaniana, etc. These have a different chromosome count than other Passiflora and so are only compatible with other series dysosmia.) seedlings that I sprayed with oryzalin last spring, some of which appear to be successfully converted, but I haven’t ran flow on them yet.
An update on identifying polyploids: One thing I touched on, but didn’t go into great detail was the physical changes in appearance due to polyploidy. I had a friend at UF do an experiment in creating polyploids in Fragaria species, as many wild species are diploid while the domestic strawberry, Fragaria x ananassa, is octoploid (which is in fact a hybrid of two naturally octoploid species, F. virginiana and F. chiloensis). What he found out is a good prognosticator of polyploidy is the depth of jagged leaf edges. If you look at the gallery of my conversions you can see this is true on the P. edulis x incarnata; the root sprout lacks the deep jagged edges. The other thing you will notice is that the oryzalin induced polyploidy creates erratic jags, while the natural polyploid tends to look more… natural. This diagnostic is a good tool to use in field identification of natural tetraploids, which often aren’t flowering when you see them. This doesn’t work on varieties with smooth leaf edges, like P. caerulea. Leaf thickness isn’t always a good indicator, either; if the same variety is grown in full sun vs. full shade, the one in the sun will have bigger, thicker leaves.
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