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Topics - Klaus Brugger

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There's a really cool publication by Prof. dr. hab. Wojciech Święcicki listing hundreds of pea genes and providing good pictures of the associated phenotypes for many of them:

Święcicki, W. (2018): The Catalogue of Pisum Genes: Gene resources maintained at the Polish Pisum Genebank. Poznań.

Greens & Brassicas / Watermelon Radish × Purple-Skinned Radish
« on: 2021-01-17, 11:22:28 AM »

I just wanted to quickly share some pictures of a radish project I'm currently working on.
In 2019, I crossed 'Red Meat', a classic watermelon radish with white/green exterior and red interior and 'Malaga', a small bordeaux/purple radish. I also did 'Red Meat' × 'Diana'. My goal was to eventually get a short-season spring radish with red or purple meat. The F1s were quite heterogeneous (as were the open-pollinated parents) and often showed a nice green interior where the bulb had been exposed to sunlight (first picture).

I only grew F2 plants of 'Red Meat' × 'Malaga' (all the other pictures). I wanted maximum anthocyanins in the whole plant so I already selected seeds that had a purplish or reddish color. It seemed to work, in a way, since most of my F2 plants were nicely colored – just not on the inside. It seemed like in my population, red/purple flesh was rather strongly linked to white exterior of the bulb and low anthocyanin levels in the leaves.

I'm not really sure how I'll proceed now. I kind of want to continue working with the F2 bulbs I have. I'm thinking about selecting for an intensely red fall radish. I also really like the combination of purple epidermis/cortex and green flesh but I think a cross with 'Green Meat' would get you better results in this respect. I will definitely try to stabilize the "spotted" phenotype that some of the bulbs exhibited (last picture). But maybe that's a story for another thread sometime.

Edit: Sorry, I think I just posted this to the wrong board. I just read Brassica something something  :-[.

Legumes / Tannins in pea shoots and pods
« 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. 

Cucurbits / Cucurbita moschata × C. pepo
« on: 2019-12-24, 08:25:08 AM »
An op Cucurbita moschata cultivar was pollinated with either of two op Cucurbita pepo cultivars from different subspecies or their hybrid. Eight moschata × pepo F1 plants were grown and pseudo-backcrossed to pepo. Ca. 120 pollinations resulted in ten fruits from four plants. BC1 seeds are poorly developed. Bigger or better filled ones will be sown in 2020. Photos including some pictures of hermaphroditic flowers are below the text.


In 2017, I started a breeding project for a high-quality pepo winter squash by crossing 'Jack Be Little' (JBL) with 'Tonda Padana' (TP). The first one belongs to the acorn cultivar group, subsp. texana, (Gong et al., 2012), while the second one is a pumpkin in the strictest sense, subsp. pepo (compare Paris, 1986).
In 2018, as a side project and out of curiosity, I made quite a few pollinations on the Japanese high-quality moschata 'Kogigu' (K), with pollen from JBL, or TP, or JBL × TP F1. I did not count the pollinations but obtained five mature fruits with some half-filled, viable seeds. The reciprocal crosses with K as the pollenizer did not yield any fruits, even though Wall (1961) stated that crossing is more difficult when moschata is the female parent.

I like good pepo winter squashes because of their starchy flesh, their flavour when roasted, their looks, and their general performance in the field especially in wet and cool years. Including moschata in my pepo breeding project is interesting to me for several reasons. They seem to be somewhat tolerant to the viral diseases relevant here, at least in that they don’t really show symptoms on their fruits. I like the scent and flavour of raw moschata winter squashes. I think eating quality of immature fruits is a valuable trait also in winter squashes and I think moschata can improve pepo cultivars in this respect. In fact, moschata cultivars seem to be the preferred summer squashes in some regions of the world (Decker-Walters & Walters, 2000) and “tromboncino” and “avocado” type squashes seem to have been gaining popularity in the US in recent years. Additionally, moschata is especially heat resistant and moschata fruits often develop a waxy bloom that protects them from the sun and imparts good keeping quality (Andres, 2004). Of course, also carotinoid concentrations and profiles of some moschata cultivars can be interesting, but 'Kogigu' does not have an exceptionally dark or reddish flesh.

Growing the first interspecific hybrid generation

I was able to establish ten healthy plants, two of which I lost later in the season before they had flowers. A few more seeds did germinate, but I discarded all distorted seedlings (there might have been a virus infection). Nine of the ten plants were from the pollinations with the intraspecific pepo hybrid JBL × TP. This might have been because of higher gametic diversity (Wall & York, 1960).
I pseudo-backcrossed the plants to pepo, using pepo as the male parent, in order to overcome possible male sterility or self/sib incompatibility. I used pepo plants (primarily JBL × TP F2) as pollenizers because moschata is already the plasmon donor and I want to prevent the progeny from approaching a moschata species type (after all, my ultimate goal is an improved pepo winter squash).
More than 120 controlled pollinations yielded ten fruits from four plants. For a while, I removed openly pollinated immature fruits to avoid competition for resources. I was especially concerned about possibly better fertilization through the open pollination: I read that zucchini selectively abort fruits on the basis of seed number (Stephenson et al., 1986) … Later in the season, I stopped removing fruits to get more fruits overall (and from more different plants) for phenotypic evaluations (including tastings ;-)). Quite a few fruits from open pollinations did ripen before the first frost.

Traits of the interspecific hybrids

Since one of the parents was an intraspecific hybrid, the first interspecific hybrid generation was quite heterogenous. The following notes are just some general observations.
The leaves of the hybrid plants looked somewhat intermediate between the parental species. Silver leaf mottling started late and was not very pronounced.
The stigmata were quite orange, more resembling moschata (Křístková et al., 2004). The male flowers produced lots of pollen – something that I did not really expect – and were heavily visited by honeybees. I cannot say anything about pollen viability though – I only tried one self-pollination, which failed. One plant made peculiar hermaphroditic flowers instead of male ones with stamina and carpellate structures but not too well-developed ovaries. No fruits formed from these flowers.
I had feared that the fruits of these hybrids might be bitter, because there is a paper describing fruits of a hybrid between non-bitter cultivars of C. mixta/C. argyrosperma (a close C. moschata relative) and C. pepo being bitter (Borchers & Taylor, 1988). However, both immature and mature fruits tasted fine.
Immature fruits reminded me more of moschata summer squashes. Mature fruits had a “melony” moschata scent when raw but a more pepo-like potato and chestnut flavour when baked. The most important thing to me, however, was the obviously high starch content inherited from the pepo parent. The baked fruits had a great dry and non-stringy texture.
The exterior of many fruits looked almost like pure moschata, but some fruits clearly did show characteristics of both parental species (e.g. waxy bloom and a distinct noncontiguous pepo striping pattern).


Most harvested seeds were rudimentary or very badly filled. I hope that some of the better developed ones (zero to three per fruit) will be able to germinate and give rise to a BC1 generation. Fruits from open pollinations later in the season did not necessarily have more filled seeds per fruit, but some seeds are really well-filled. I probably will not grow these, however, since many different varieties, including some from a neighbouring field, are possible fathers. In case that I can get some BC1 seedlings established, I am planning to allow them to inter-pollenize freely, if I can find a location isolated enough.


Andres, T. C. (2004). Diversity in tropical pumpkin (Cucurbita moschata): cultivar origin and history. In A. Lebeda & H. S. Paris (Eds.), Progress in Cucurbit Genetics and Breeding Research. Proceedings of Cucurbitaceae 2004, the 8th EUCARPIA Meeting on Cucurbit Genetics and Breeding. July 12––17, 2004. (pp. 113–118). Retrieved from

Borchers, E. A., & Taylor, R. T. (1988). Inheritance of Fruit Bitterness in a Cross of Cucurbita mixta x C. pepo. HortScience, 23(3), 603–604.

Decker-Walters, D. S., & Walters, T. W. (2000). Squash. In K. F. Kiple & K. Coneč Ornelas (Eds.), The Cambridge World History of Food. Volume One (pp. 335–351). Cambridge, United Kingdom: Cambridge University Press.

Gong, L., Paris, H. S., Nee, M. H., Stift, G., Pachner, M., Vollmann, J., & Lelley, T. (2012). Genetic relationships and evolution in Cucurbita pepo (pumpkin, squash, gourd) as revealed by simple sequence repeat polymorphisms. Theoretical and Applied Genetics, 124(5), 875–891.

Křístková, E., Křístková, A., & Vinter, V. (2004). Morphological variation of cultivated Cucurbita species. In A. Lebeda & H. S. Paris (Eds.), Progress in Cucurbit Genetics and Breeding Research. Proceedings of Cucurbitaceae 2004, the 8th EUCARPIA Meeting on Cucurbit Genetics and Breeding. July 12–17, 2004. (pp. 119–128).

Paris, H. S. (1986). A proposed subspecific classification of Cucurbita pepo. Phytologia, 61(3), 133–138.

Stephenson, A. G., Winsor, J. A., & Davis, L. E. (1986). Effects of Pollen Load Size on Fruit Maturation and Sporophyte Quality in Zucchini. In D. L. Mulcahy, G. B. Mulcahy, & E. Ottaviano (Eds.), Biotechnology and Ecology of Pollen (pp. 429–434).

Wall, J. R. (1961). Recombination in the genus Cucurbita. Genetics, 46(12), 1677–1685.

Wall, J. R., & York, T. L. (1960). Gametic diversity as an aid to interspecific hybridization in Phaseolus and in Cucurbita. Proceedings of the American Society for Horticultural Science, 75, 419–428.


I wonder what's the best "not too destructive" way to evaluate the interior of radishes, e. g. for flavor or "flesh" color.
I'm especially interested in small round ones that are primarily hypocotyl.

Do you cut out a "sector"? Or cut off a "cap"? Or is there another, better method?

Thank you very much!

Plant Breeding / Sesame for temperate regions
« on: 2019-01-26, 04:48:47 PM »

Is anyone working with or growing sesame in more temperate regions?
I read that there is great variation among varieties regarding maturity time and response to photoperiod and temperature.
I'm thinking about starting a breeding project and as a first step I'd like to trial some southern US heirlooms (benne) if I can track down a few. Apparently they have a high culinary quality?


Plant Breeding / Open Source F1 Hybrids
« on: 2018-12-26, 03:50:25 AM »

I’d like to start a discussion thread on hybrid breeding. What are your thoughts on hybrids in the context of open source breeding and small freelance breeders?

I think there are three main possible advantages:
Exploiting heterosis, reaching high phenotypic uniformity in crossbreeding species, and, at least theoretically, developing useful new cultivars in a very short time by just crossing lines you already have.

On the downside, of course, there’s reduced genetic variability compared to genetically diverse open-pollinated/population cultivars. Seed sovereignty doesn’t have to be a problem: You just have to make your parent lines available.

Looking forward to reading your thoughts,

Cucurbits / Bitterness in interspecific squash hybrids
« on: 2018-12-21, 08:38:32 AM »

I'm very much interested in crosses between domesticated Cucurbita species, mostly in order to transfer quality traits among the species. Have you ever encountered bitter fruits in hybrids between edible cultivars of different species, particularly in crosses with C. pepo? I already have a few seeds C. moschata × C. pepo F1 that I will trial in 2019, but I'd like to hear some experiences or thoughts for my season planning. There seems to be one particular paper* about C. argyrosperma × C. pepo and since C. argyrosperma and C. moschata are quite close, I fear that I might have to deal with cucurbitacins in my progeny.

Thank you,

*Borchers, E.A. and Taylor, R.T. (1988): Inheritance of fruit bitterness in a cross of Cucurbita mixta x C. pepo. HortScience, Volume 23, pp. 603–604.

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