Very interesting topic!
I've tried to find some information about the inheritance of flesh color a while ago. There are some Chinese papers like Zhang (2006) or Lv et al. (2015), but I cannot find or access all of them.
Chen et al. (2016) have found higher expression levels of a few genes in intensely red radish.
One thing I think we have to consider is that modes of inheritance might not be the same in all cross combinations. Radish seems to have been domesticated at least three times with small European radishes and black radishes apparently being of different origin, having quite different cytoplasms (see Yamane et. al, 2009 and Li et al., 2021). This might be an explanation why Dan Brisebois had purple flesh in his black × watermelon radish F
1 but my purple small × watermelon radish F
1 didn’t show any anthocyanin in the flesh.
I must say I have very little personal experience (or theoretical knowledge!) with yellow radishes, so please don’t give the following thoughts too much weight …
I’m not sure what actually causes the yellow color. It seems to be associated with a certain structure of the skin, not unlike the black color. In fact, I wonder if yellow, brown, grey and black might essentially be the same character. Take, for example, a brownish cultivar like the open-pollinated German 'Fetzers Maindreieck' (
picture). To me, it looks somewhat like an intermediate between yellow and black.
The yellow color of radishes seems to be different from the yellow color of turnips, where yellow-skinned bulbs can have a quite intensely yellow flesh too. Maybe I’ll cross a black and a yellow turnip this year. Of course, radish and turnip are also somewhat crossable. And maybe introducing genes from yellow-flowering
Raphanus raphinistrum into cultivated radish would be interesting, too.
The plants on the NYC farmer’s market look like beets to me (as has already been mentioned in the other
thread), with a nice combination of different betalains ('Touchstone Gold' looks similar). However, I think an orange radish (a yellowish structure on top of a red or pink cortex …) is a very interesting breeding goal.
By the way, I just found a cool paper by Chen et al. (2021) where they show that anthocyanin accumulation may be enhanced by inducing tetraploidy. White tetraploid radishes of cultivar 'Rex' are commonly grown in home gardens, so tetraploidy definitely works for vegetable radishes.
Literature:
Chen, F. B., Xing, C. Y., Huo, S. P., Cao, C. L., Yao, Q. L. & Fang, P. (2016). Red Pigment Content and Expression of Genes Related to Anthocyanin Biosynthesis in Radishes (Raphanus sativus L.) with Different Colored Flesh. Journal of Agricultural Science, 8(8), 126-135.
https://doi.org/10.5539/jas.v8n8p126
Chen, F., Gao, J., Li, W., Liu, Y., Fang, P., & Peng, Z. (2021). Colchicine-induced tetraploidy influences morphological and cytological characteristics and enhances accumulation of anthocyanins in a red-fleshed radish (Raphanus sativus L.). Horticulture, Environment, and Biotechnology, 62(6), 937–948.
https://doi.org/10.1007/s13580-021-00363-w
Li X, Wang J, Qiu Y, Wang H, Wang P, Zhang X, Li C, Song J, Gui W, Shen D, Yang W, Cai B, Liu L, Li X. SSR-Sequencing Reveals the Inter- and Intraspecific Genetic Variation and Phylogenetic Relationships among an Extensive Collection of Radish (Raphanus) Germplasm Resources. Biology. 2021; 10(12):1250.
https://doi.org/10.3390/biology10121250
Lv, F. S., Tao, H. Y., Tan, G. X., & Zeng, X. X. (2015). The characteristics of parents and seed production techniques of red radish “Yanzhihongyihao”. Shanxi Agricultural Science, 61, 122-123.
Yamane, K., Lü, N., & Ohnishi, O. (2009). Multiple origins and high genetic diversity of cultivated radish inferred from polymorphism in chloroplast simple sequence repeats. Breeding Science, 59, 55-65.
https://www.jstage.jst.go.jp/article/jsbbs/59/1/59_1_55/_pdf/-char/ja
Zhang, L (2006). Inheritance of main botanical characters in radish (Raphanus sativus L.). China Vegetables, 10, 10-12.