Posts

Posted on

Variation in seed dormancy within populations

I asked Robin Probert at the Millennium Seed Bank at Kew to comment on the recent paper “Variation in seed dormancy quantitative trait loci in Arabidopsis thaliana originating from one site.” Here’s the abstract:

A Quantitative Trait Locus (QTL) analysis was performed using two novel Recombinant Inbred Line (RIL) populations, derived from the progeny between two Arabidopsis thaliana genotypes collected at the same site in Kyoto (Japan) crossed with the reference laboratory strain Landsberg erecta (Ler). We used these two RIL populations to determine the genetic basis of seed dormancy and flowering time, which are assumed to be the main traits controlling life history variation in Arabidopsis. The analysis revealed quantitative variation for seed dormancy that is associated with allelic variation at the seed dormancy QTL DOG1 (for Delay Of Germination 1) in one population and at DOG6 in both. These DOG QTL have been previously identified using mapping populations derived from accessions collected at different sites around the world. Genetic variation within a population may enhance its ability to respond accurately to variation within and between seasons. In contrast, variation for flowering time, which also segregated within each mapping population, is mainly governed by the same QTL.

And here’s what Robin had to say:

Sufficient genetic variation for seed dormancy in single populations, especially annuals, is not surprising and we found this many years ago when we were working on Ranunculus sceleratus. 1 In those days we didn’t have the molecular tools now available but is was very clear that individual genotypes selected from single populations had the ability to behave as winter or summer annuals. Nevertheless, there are countless examples in the literature that demonstrate that germination and dormancy are highly adapted to local climate. I guess what the recent papers reveal is that hidden within those striking patterns of adaptation is sufficient genetic variation to cope with climate variation. Whether this will be enough to cope with the scale and rapidity of climate change is another matter. Time will tell.

Indeed it will. While we wait, can anyone explain that “In contrast…” at the end of the abstract?

Posted on

Even heirloom tomatoes may not be what they seem

ResearchBlogging.org Oh, pesky scientists! A bunch of them in Spain has taken a close look at one of the darlings of European tomato culture and found it, how shall we say, disappointing. 2 The subject of their investigation was a type of tomato known as Marmande, associated with the town of that name. There are several landraces of Marmande tomatoes, and in northeast Spain two of them, Montserrat and Pera Girona, are grown in adjacent areas. Each has its favoured consumers, who argue that their Marmande is better than the others’, although both Montserrat and Pera Girona are apparently facing competition in their respective niches from upstart Marmande tomatoes from France, Italy and elsewhere in Spain.

The researchers note that:

Often without experimental confirmation, many consumers consider that everything “traditional” tastes better than improved varieties.

Marmande tomato And they’re not going to stand for that. So, they went to growers and got samples of the two kinds of Marmande, a couple of controls from further afield, and some commercial varieties, grew them in the field and evaluated the hell out of them, including a slew of molecular tests. And here’s the bad news; while the controls and far-off Marmandes were quite distinct from one another and from Montserrat and Pera Girona on molecular data, those two could not be separated from one another, favoured consumers be damned. There were differences in the outward look of Montserrat and Pera Girona, but within each landrace the range of scores on sensory traits (what consumers are probably “preferring”) was far greater than any differences between the two.

There are differences, of course, mostly in what the two varieties look like. Montserrat has flattened fruit, while Pera Girona is pear-shaped. So, what’s going on? Farmers are clearly selecting to conform to the landrace stereotype, but not much else.

[T]he recent evolution of these tomato landraces has resulted in uniform fruit morphology and wide variation in texture, aroma, and taste. It seems farmers have selected seeds solely on the basis of fruit morphology, neglecting sensory traits. Texture, aroma, and taste do not correlate with the shape of the fruit; thus, the persistence of separate markets for these varieties is exclusively due to morphological differences in the fruit. It seems that consumers continue to identify certain morphologies with superior quality.

And this is by no means a unique phenomenon.

Selection for morphological traits while neglecting sensory traits seems to be practiced widely: variability in sensory attributes related to a genetic base has been reported in beans … and in eggplant. … In other cases, variability in sensory traits is related to cultivation practices, as in the RAF tomato, which can be acid, sweet, and crisp when cultivated in salty soils but of poor sensory value when cultivated in high yielding soils. As a result of cultivation expansion, the prestige of RAF tomatoes blossomed and wilted in a short time.

Inevitably, then, consumers are going to be disappointed by their chosen landrace at least some of the time. What’s to be done?

In order to consolidate the market, the link between organoleptic and morphological traits must be maintained and reinforced.

In other words, get back to basics: gather a group of keen consumers, identify what it is about each variety that attracts them, and then start selection to make sure that the tomatoes deliver more than appearance. As good as their word, the scientists have already done this for Pera Girona, and they say that just one round of selection has already “resulted in an improved inbred line”.

Ah, but is it still a traditional landrace?

Posted on

What’s wrong with Commons anyway?

The abstract of a new paper in PNAS is fascinating. The paper is called Risk of collective failure provides an escape from the tragedy of the commons, and what it seems to be saying is that a small group, which will pay dearly for failure, is more likely to manage a commons successfully. This seems deeply obvious. Garrett Hardin himself said that one of his biggest tragedies was the failure to call his ground-breaking 1968 Science paper The Tragedy of the Mismanaged Commons, for there is nothing inherently tragic in the idea of a commons. 3 Exclusive community rights, and shame, he reckoned, were usually enough to keep a commons sustainable. So I’m probably missing the point, and I currently don’t have access to the full paper to find out what Santos & Pacheco, authors of the paper, are saying in full. Take this bit from the abstract, for example:

We also offer insights on the scale at which public goods problems of cooperation are best solved. Instead of large-scale endeavors involving most of the population, which as we argue, may be counterproductive to achieve cooperation, the joint combination of local agreements within groups that are small compared with the population at risk is prone to significantly raise the probability of success.

Does this mean that we should leave it to politicians or professional negotiators to hammer out global agreements? Surely not as long as they require our approval, or (financial) support. And how might the conclusions of Santos & Pacheco apply to, say, negotiating access to the global “commons” of genetic resources? Answers on a postcard please.

Posted on

Brainfood: Medic systematics, Fruit wine, Alfa paper, Marula diversity, Cardamon pollination, Protein, Ants, Peanuts, Truffles, Ethiopian barley, Citrus diversity, Biofuel trees, Honeybush, Czech garlic