In an earlier posting I’d stated that I thought I’d gotten a cross between a runner bean and a common bean:
Thanks to a couple of articles I’ve found I can confirm that such a cross happens, and even give some idea as to how. The answer is that those Carpenter Bees I love so much are the likely means to that ends.
First up, a review of the bean in question:
Top is a dry Scarlett Runner Bean pod, bottom is a set of three normal sized common beans (2 purple pod, one Cherokee Trail Of Tears). The ruler shows that in between are some 19 cm long ( about 8 inch) Giant Purple Pod beans.
In that prior article I’d noted:
My beans are regularly visited by a bunch of pollinator species. 4 kinds of bee, a couple of different humming birds. The cross pollination delivery was there. But who knows.
I’ve seen a bumble bee (fuzzy body and all), a European Honey Bee, and what was originally thought to be 2 kinds of carpenter bee, but in fact are the two sexes of xylocopa varipuncta, also known as Valley carpenter bees, as discussed in this comment:
So who crossed what with whom can be a bit of an “issue”…
There were three articles I ran into on crosses of Phaseolus Vulgaris and Phaseolus Coccineus. They pointed out that:
a) It can be done and has been done.
b) As the Phaseolus Coccineus tends to open the flower before pollinating, it crosses out well, but as the Phaseolus Vulgaris tends to “self” prior to the flower opening, it tends to not cross … UNLESS the flowers have been “serviced” by carpenter bees that tend to open a hole in the flower to get to the pollen and can deliver some “coccineus” pollen to a “vulgaris” that has not yet “selfed”. Thus my beans with a purple pod “mom” and runner bean “dad”.
Runner beans are usually grown as annuals (I’ve just sown what I hope will be an early crop) but they are perennials in the wild and if you can keep the roots frost-free through the winter they’ll produce a second year’s growth, albeit with inferior pod production. If you are of a curious nature and fancy some amateur plant breeding you could try crossing French beans with runner beans, by carefully removing stamens from French bean flowers with fine tweezers before they shed pollen and then pollinating the flowers with runner bean pollen a day or two later. The cross works with French beans as the female parent, but not the other way about.
I would question that it can go “the other way about” as I’ve got some slightly odd “pods” from the runner bean that I think just might be that other way. Only 3 total seeds, but still, it’s a start…
The variation of F2 progenies derived from interspecific crosses between Phaseolus vulgaris and Phaseolus coccineus
Anton IVANČIČ and Metka ŠIŠKO
Interspecific hybridisation within the genus Phaseolus represents an important source of genetic variation which can be very useful in breeding programmes based on recurrent selection. The aim of this investigation was to analyse the phenotypic variation and relationships among the most important quantitative traits in F2 generation materials derived from crosses P. vulgaris x P. coccineus. P. vulgaris was used as female while P. coccineus as male parent. The F2 material was composed of 825 individuals which originated from open pollination of 65 F1 plants. The most variable quantitative trait was the number of flowers per inflorescence, which varied from 0 to 57 (CV = 45.8 %). The second was the inflorescence length which varied from 2.5 to 74 cm (CV = 39.0 %). The highest value (CV = 70.4 %) was obtained for floral colour (a qualitative trait which was transformed into a special numerical scale). The correlation analysis showed that there were close relationships among the number of leaves, number of flowers, number of pods, number of seeds and the length of the growth period. For practical breeding, the most useful is probably the correlation between the number of inflorescences and the number of seeds per plant (r = 0.503 and 0.560) because the number of inflorescences can be easily determined at the beginning of the hybridisation period, and the number of seeds is more or less directly associated with the yield. For the final visual selection, at the end of the vegetation period, the most useful trait is the number of pods, which is highly correlated with the number of seeds (r = 0.740 and 0.916).
Agricultura 2: 19-25 (2003)
So, the point of this posting?
Pretty simple, really.
It shows that the cross can happen. That it goes in the direction that I seem to have achieved. That it is typically effected by tweezers or similar surgical intervention, and we know that the carpenter bees do just such a procedure to get to the pollen and nectar in flowers too small for them to enter.
I really like my bees ;-)
There is an interesting story here:
from someone else who got such a cross. It looks, from their story, like I may need to spend a while “stabilizing the cross”.
Posted by galina england (My Page) on Mon, Feb 18, 08 at 20:04
Farmerdilla and Zeedman, you wrote:
The runner beans (P. coccineus) will cross with each other but not limas or common beans. (snip)
It is rare, but runner beans and common beans can and do cross. I had a cross several years ago, and it has been fascinating. At first I did not recognise what was happening – a common bean with red and pink flowers? But the flowers looked different from runner bean flowers. The pods were short, rough skinned, sparse, late maturing and the few black seeds they contained were of irregular size and distorted shape.
The following generation I had some cotyledons in the ground and some above. And the most exquisite flower colours imaginable. Peach, pink, purple, pale blue, apricot. The resulting beans were smooth podded and quite variable in type and yield, including just a single yellow pod on one of the plants containing two tiny seeds. One germinated and I got a very strong growing tall plant with large yellow pods and large brown seeds. Another of these second generation hybrids produced small seeds but with the same markings as the runnerbean that I suspect to have provided the original pollen.
All of the offspring of the cross have become much heavier bearing than the original cross. They still have remarkable flower trusses, but the colours are more muted now. They grow strongly and produce very well, especially later in autumn, when the ordinary beans and the runnerbeans have stopped. So far the hybrids haven’t really stabilised much. I most often get black seeds now, but some are white or other colours.
It is rare, but if you get a chance cross, it is fun following it up, even though the first filial generation isn’t very promising.
The F1 of my beans have been planted out for a while now. Way too early. (It has been much colder than “typical”). I’ve lost 3 out of 6 plants to various cold and / or hungry critter issues (probably also from the cold and reduced food sources). At this point I have three of them about 5 foot tall (and still growing! At least on warm days…) with very pretty (though small) purple flowers and some with pod set.
I still have about a dozen seeds to play with as the season warms. I would like to get some of the F1 matured before I risk the “archive” seeds, though.
All in all, it is still an adventure. But know I have a bit of an idea about the “how” and the “why” of it all.
Here is a picture of the “first flower”. It is now a small pod about 2 cm long ;-)
Shortly after this stage it opens and becomes a lighter more violet color. As you can see, the same gene that codes for “purple flower” also codes for “purple in the stem” (and a bit of purple cast to the leaves). I think there are 3 total flowers in that picture. You can pick them out by the three shades of purple.
All in all, a beautiful flower.
So far all of the F1 have the “vulgaris” style of holding the cotyledons out of the soil. We’ll see if the F2 continues that trend (probably next year). So far it looks like “mom” gives the cotyledon style and color of pod, while “dad” gives an overall more intense color and larger seed size. As we move to the F2 generation, that could get more “mixed up”…
Again, “well see”.
That I’m getting pod set, even in the cold weather I’m having, is an encouraging sign. The purple pod vulgaris beans are known for being cool soil tolerant, and the runner beans are known for setting pods in cool weather. IFF I’ve done what I hope to have done, I’ve got a fairly cold tolerant bean that will set pods and make beans even in this “60 F or so with overcast and sporadic rain” type of weather. (It is raining again today… Very nice April weather… in late May…)
Add that to my “Kalards” that have done a wonderful job of “self sowing” and are now making plenty of greens, and I’m well on my way to a cold tolerant garden with adapted species that will give me both greens and seeds. Edible pods and dry beans.
“Just in time” variety creation… Gotta love it!