Saving runner bean seeds

Good afternoon everyone,
well apart from one tomato, one cucumber and a dozen chili plants (turning red from black), the greenhouse is empty.

Our 1 huge runner bean plant (Painted Lady) has some pods where there is only one seed inside.  If I store these seeds will this single seed pod characteristic prevail or will we have 'normal' pods next year?

Cheers,  Tony.

The number of beans inside the pods, relies on successful pollination....so, in theory that should have no bearing on the future performance of the plants grown from them. Painted Lady is a very old variety and usually reliable, given enough pollinators.

Good afternoon everyone,
well apart from one tomato, one cucumber and a dozen chili plants (turning red from black), the greenhouse is empty.

Our 1 huge runner bean plant (Painted Lady) has some pods where there is only one seed inside.  If I store these seeds will this single seed pod characteristic prevail or will we have 'normal' pods next year?

Cheers,  Tony.

The single-seeded pods are likely due to a couple of factors. 

(1) Partial pollination, as JayG mentioned, and

(2) drop in soil fertility or plant vigor toward the end of the growing season. Although we are always told that beans "fix their own nitrogen" which is true, they also use the N-P-K and other nutrients that we supply to them.  This year, I paid a lot more attention to providing fertilizer to my French beans (pole variety, Kentucky Wonder).  The bean pods are longer (7 to 10 inches), there are more of them, and for the pods that develop immature beans before I pick them, there are more beans per pod.  Those beans have protein, and because protein has a significant nitrogen content, the plant needs to have nitrogen readily available in the soil to produce well.

How can a bean get partial pollination whn there is only one flower, it's either pollinated or not aint it? 

It was basically an assumption on my part which may not be correct Klefti (can't find a definitive answer on the web.)

Since both you, me and no doubt many others have had short bean pods with only 1 or 2 seeds in, because it usually starts happening late in the season it could be that the plants are just too weak to completely fill all their pods, although I must admit I've found similar short beans much earlier in the season too...

Not been much help have I? 

How can a bean get partial pollination when there is only one flower, it's either pollinated or not aint it?

1 flower doesn't equal 1 seed, though, does it?
Think of a single pea flower and number of peas in the pod.... sometimes just one gets fat sometimes the whole pod is full. Depends on whether all stamens inside the flower get fertilised..

Weather also plays a part

Water and heat stress can also play havoc on bean production. Hot days and hot nights dry the plant out and reduce the seed numbers or result in underdeveloped seeds (flat pods). This is more prevalent in large-seeded pole lima beans.

https://www.gardeningknowhow.com/edible/vegetables/beans/lima-pods-are-empty.htm

Much the same reasoning as Sp, but thought I'd post it anyway