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« on: 2020-12-26, 05:31:32 AM »
Last year, I found a single seed with clear testa and hilum in a packet of 'E.F.B. 33' winter peas. I hope that it's a mutant that will allow me to compare shoots and pods of white-flowered/low-tannin and purple-flowered/high-tannin peas of the same genetic background.
I'm curious about your opinions on or experiences with white- vs. purple-flowered varieties for shoot and pod use.
I've written this little text with some literature references for a different platform, but maybe it's interesting for some of you:
In peas, a lack of pigments in hilum and seed coat is associated with seeds* of lower tannin levels and, consequently, a “sweeter” taste [1]. The same genotype confers a lack of anthocyanins in the whole plant and, presumably, also reduced tannins throughout the plant. For this, however, I only have “anecdotal evidence”, like white-flowered forage peas being marketed as more palatable and purple mangetouts often having a rather astringent taste. Interestingly, in a tasting of pea shoots of one purple-flowered and three white-flowered winter peas, the purple-flowered variety ('E.F.B. 33') came out on top [2]. In this picture, you see both the pigmented seeds of 'E.F.B. 33' and seeds grown from a single seed with clear hilum/seed coat I found in a packet of 'E.F.B. 33'. I hope that this line proves to be a mutant only differing from 'E.F.B. 33' at the locus of interest (comparing UPOV characteristics will at least enable me to make a guess). Having such “near-isogenic lines” available could permit conclusions about taste differences between shoots of low tannin and high tannin peas.
Generally, near-isogenic lines are lines possessing almost, but not quite, the same genotype as their sister or parent line. Typically, they are generated by recurrent backcrossing where after several generations they differ from their recurrent parent merely at the locus under selection. They then can be used in phenotyping experiments to determine the effects of polymorphisms at this one locus.
Another reason why it would be nice to have a white-flowered line near-isogenic to 'E.F.B. 33' is because 'E.F.B. 33' ranks among the most winterhardy pea cultivars. Winterhardiness seems to be linked to presence of anthocyanins in traditional winter pea material [3] but this linkage might have been broken in newer varieties. Today, several white-flowered varieties with good winterhardiness exist, some even being semi-leafless, a trait morphologically associated with a higher susceptibility to freezing injury as shown in experiments with – yes! – near-isogenic lines [4].
*While tannins are present in the seed coat, in the cotyledons bitter tasting saponins play a more important role [5].
[1] Clark, S. (2019): Pea (Pisum sativum L.) Characteristics for Use and Successful Planting. USDA, NRCS, Big Flats, NY. Plant Materials Technical Note No. 19-01.
[2] ARCHE NOAH (2019): Aktivitätsbericht Zuckererbse. Sorten- und Produktentwicklungen aus Gemüseraritäten in der Region Kamptal in einem partizipativen Prozess: LEADER-Projekt März 2016 – Februar 2019.
[3] Markarian, D., Harwood, R.R., & Rowe, P.R. (1968): The inheritance of winter hardiness in Pisum II. Description and release of advance generation breeding lines. Euphytica, 17, pp. 110–113.
[4] Étévé, G. (1985): Breeding for Cold Tolerance and Winter Hardiness in Pea. In: P.D. Hebblethwaite, M.C. Heath, & T.C. Dawkins (Eds.): The Pea Crop: A Basis for Improvement London, Butterworths, pp. 131–136.
[5] Tulbek, M.C., Lam, R.S.H., Wang, Y.(C.), Asavajaru, P., & Lam, A. (2017): Pea: A Sustainable Vegetable Protein Crop. In: S.R. Nadathur, J.P.D. Wanasundara and L. Scanlin (Eds.): Sustainable Protein Sources, London, Academic Press, pp. 145–164.
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