Peas - Powdery mildew

[andi]

My peas die of powdery mildew every year ...  It is just now happening again. So far I have refrained from saving seed of them, because I have read somewhere to never save seed from infested plants and this concept makes sense to me. But I will definitely not stop growing peas; I love them to much and the do give me an Ok crop nevertheless. But since I get PM anyway, what harm could it do to save my own seeds?
Also I`m thinking about making some crosses to perhaps be able to enhance their resistance of PM. Then I would need to save the F1-seed from the infested motherplants. The seeds are still likely to sprout and grow, right?
Anyone know of any tricks to cope with this plague in some way without cides or lots of effort?

[ferdzy]

Yeah my peas always get PM and I save seed anyway and next year they get PM. I'm not sure it's getting much better but it isn't getting worse.

I spend a fair bit of time sorting peas. I pull up each plant individually and assess it. Less PM is definitely something I look for, along with a fair number of pods. Once I have a pile of my best plants (or actually their pods as I strip the plants as I go) I shell out each pod and determine a number of peas per pod that each must have in order to qualify as seed. Do this for a couple of years and you will be amazed at how much your peas improve. It's tedious work though; shelling and counting peas is a good TV watching time project.

There are some threads on crossing peas on this forum. I will tell you right now though, it is quite hard to do it yourself. I have learned to know my peas fairly well and recognize when naturally occurring crosses come up, and have gotten some interesting things that way. Some people do cross 'em though.

Also, just before planting soak your peas in hydrogen peroxide. I do it half and half with water, overnight, and give them lots because they soak it up.

[templeton]

Hi andi,
There are PM resistant peas.
There are two different genes that both confer resistance. Best resistance occurs when both genes are present. Both are recessive, so relatively easy to recover, but they won't occur in an F1 population of resistant X non-resistant cross, since a recessive gene needs to be homozygous for expression - you would expect 1/4 of the F2 population to express one of the resistant genes from such a cross, or 1/16 to have both the PM resistant genes if one of the original parents had both.
I disagree with ferdzy - I reckon crossing peas is easy, with a little care and practice.
There are a number of strategies you can use to reduce PM - increase air flow, reduce moisture on leaves - plant in open rows with good air circulation, don't water the foliage, prune to keep the foliage open - this is very tedious. I suspect there might be horizontal resistance strategies that could be used - semi-leafless peas have less foliage=more air ciculation, and I suspect there are leaf surface characteristics that might be explored that would help.
I've observed a number of different survival strategies in peas from full resistance - the plants just don't get PM while their neighbours do, through to getting the disease but still growing and producing, through total succumbing.

get out the forceps and start breeding!
T

[steve1]

templeton, is there any breakdown of resistance that you know of to the Er-2 gene (which was the commonly used one (and is in Super Sugar Snap as I recall) ? I know there are others but I hadn't heard of them being used. If so what varieties are the others in?
andi and ferdzy, T is right make some crosses, they are large easy flowers. If you are trying to sterilize seed, 1/4 strength sodium hypochlorite or household bleach with a drop of dishwashing detergent agitated for 10 mins should do the job. That'll knock off most fungi including PM and ascochyta I would think. You don't really want your seeds to imbibe bleach I suspect, sounds detrimental to germination. Just my thoughts.
Cheers and good luck
Steve

[ferdzy]

All I can say is yous guys have better eyes and steadier hands than I have...

I have managed to do it. Once or twice. Won't say how many attempts I've made. Okay, I will - so far it seems to be about 10 tries to one success. Maybe I could get better at it, but neither eyes nor hands are improving.

[walt]

One in ten is doable.  I shared a lab in grad school with another grad student and a post-doc who were crossing wheat and barley.  They figured it costs $40,000 in wages for each seed that reached maturity and produced at least one back-cross seed.
It gave me a warped view of what is easy to cross and what is hard to cross.
Of course, in your own garden you are the sole person who decides what is worth your time and what isn't worth it.

[steve1]

Yep I have a Pisum fulvum x sativum cross to do, only literature I can find suggests it is a 1/30 cross. I'm set to do 90. Doing crosses in the open is a pain. Earlyish morning and preferably in a greenhouse is optimal. Have a look at the pea crossing thread... I think Rebsie started that one...

[templeton]

steve1, by breakdown do you mean where the disease has overcome the resistance? Sorry, I haven't done any research into it. My comments are from some observations i did a few years ago in one of my growouts, as I recall, in the same row I had very sick plants, uninfected plants, and plants with considerable bloom of Pm on them, but still powering along.
AS for genetics, my Jupiter has pretty good PM resistance, but which genes its carrying i don't know - I did give you some Steve1 didn't I? If you need more let me know asap coz I'm offline for a couple of months soon.
T

[steve1]

No worries templeton . As far as I am aware the ER-2 hasn't broken down and there are variable reasons why the Pm R genes aren't used commonly. Thanks for the offer but all good. Sorry for the extra late reply.

[steve1]

templeton, sorry was doing some reading and it's the recessive er1 that's commonly used - not the Er2 I've posted above. Er2 and Er3 though, are described as less effective from what I've read and Er3 is found in Pisum fulvum, so there is some extra joy of interspecific crosses and incompatabilities in that one.

Cheers
Steve