27 August 2012

Pea Pod Colouration in the F2

I'm growing out the first batch of F2 Snow X Purple peas. They have taken quite a while to develop pods - five months!.
And they haven't produced purples in the ratios I would have expected - but more on this when I do a final tally.

Of interest today is the way the purple colour is distributed on the pods. One plant has given pods that are mostly purple

 The next is mostly purple, but with green areas

...and on another plant, complementary colouration, what I'm calling 'purple dusted'. Neat how the two genes fill in each other's gaps to get full purple.

25 August 2012

Pea seed emergence

Over the past week have sown half of my F2 seeds of Chamber of Death X Purple Podded (select organics) - I'm holding half back in case of failure.
The seeds had segregated, for purple dusting, tan, and green, all with several degrees of dimpling, so I germinated them seperately in ziplock bags on a heat pad. I was hoping that the seed coat colour would help me select for purple coloration on the plants, saving me garden space for growouts. There has been considerable differences in germination rates, with the purple dusted germinating the quickest, then the tans, and the greens, of which there were the fewest seeds, have only had one germinate so far.
It seems that seed coat colour might be linked to late emergence.

24 August 2012

Re-thinking crossing strategies

Well its almost a year since I germinated my first peas to develop an antipodean purple snow pea. And I've had a chance to take stock. I dived in, without thinking through a strategy to optimise success. In part, this was due to some time pressures - rationally assessing each variety, sitting down and thinking through possible crosses, and then waiting another year to do the crosses just didn't fit with my impatience to get cracking. So I sowed every purple. yellow and snow I could lay my hands on, and crossed as much of everything with everything else that I could, given the constraints of time and available flowers at the right level of maturity.

Problem is, I now have not quite enough seed of any one line to really explore the F2 outcomes, and too much seed of multiple crosses to be able to grow out with a good chance of success this season.

A smart approach would have been to select one purple (since my guess is the three purples available in Australia are probably all the same anyway), choose a good, tasy, disease resistant, dwarfing, multi flowered snow pea of good taste, and do multiple crosses between them to get a big whack of F1 seed to grow out over summer, with a resultant 300 - 400 F2 seeds of one line to try in autumn.
Instead, I've got (or will get) about 100-150 seeds of about a dozen crosses - not quite enough to be confident of getting the desired class in one season, which could be refined , stabilised, or outcrossed for missing phenotypes in subsequent generations. It looks like I will need a few extra generations to get the classes I want, so leaping in without proper planning in an effort to get results more quickly may have backfired. This season will tell.

While the summer growouts did give some F2 seed, even sowing these as soon as I got them didn't really give me enough time to grow out the F2 plants for F3 seed this spring - my plants are just setting pods - they were very slow over winter, and some flowers didn't set seed during the winter cold - and now is when I should be sowing the next generation to escape the hot November when seeds won't set, but the pods on the F2s are onlt just developing. Let's hope for a long spring (but with an El Nino expected, I don't like my chances).

08 August 2012

Purple podded snowpea - the next generation

The first of my winter growouts of my F1 plants are just finishing off, and I've been harvesting seed. I've been away for a month and half, and some pods matured on the plants, with the seeds inside the pods germinating in the pod - most disappointing. But I seem to have enough (more than enough, actually) to get a good crop of F2 plants to assess.

For one cross, Chamber of Death X Delta Louisa, I harvested seed last week. Subsequently inspecting the seed, I noticed 2 classes of seed - wrinkled, which are blocky and wrinkly; and dimpled, which are mostly round with only a slight dimple in the seed coat. When I harvested the seed I put it down to early harvesting of pods, and thought the wrinkled ones were just under developed. But I don't think so. Wrinkled seed coat is associated with sweet flavour (I seem to recall that it's got to do with starch development which affects both flavour and how the starch gets 'packed' in the seed).

When I had all the seed spread out to select for my spring growouts, I started separating them. They definitely fell into two classes. The F2 seeds are on the right, and the original parent stock seed is on the left.
I'm going to sow them separately, to see if they segregate for flavour.

I subsequently googled this, and found wrinkled seed was one of the characteristics Mendel used in his original experiments. It's also a embryonic trait - you can tell if the F3 plants will have the gene by looking at the seed off the F2 plants. This helps if you want to select for sweetness, and want to limit your growouts, both of which I want. But I'll see how I go growing both for this line, to see if it works out.

My other F2 growouts from my summer growing seed are just setting pods now - I do have some purples, but can't tell if they are snows, yet. All of my plants are suffering from powdery mildew, and it might be a bit late to spray with Potassium Bicarbonate, but I will give it a go  this week.