Mike Jackson’s obituary of Trevor Williams is up at Genetic Resources and Crop Evolution, and it’s open access.
Potato wild relatives: Too much of a good thing?
What do you call it when you suddenly notice things you didn’t notice that much before, and wrongly assume that their frequency has increased? Is it apophenia? Observational selection bias? I’m sure it’s a thing, though I can’t remember its name. And I’m sure it’s frequency is increasing. Meta-apophenia is rampant, I tell you. Yesterday there was that bunch of papers on plant-pest co-evolution. Today two papers on cytoplasmic diversity in potato. I mean: what are the odds? 1
Anyway. One paper looked at 1,217 European cultivars and breeding clones, 2 the other at 978 accessions, breeding lines and varieties used or released by the breeding programme of the International Potato Centre (CIP). 3 The potato comes in 6 types of maternally-inherited cytoplasmic genomes: M, P, A, W, T and D. The use of the wild species Solanum demissum and S. stoloniferum in parental line and variety development around the world, due to the fact that they have some good pathogen resistance genes, has led to the prevalence of a couple of these. The papers report that 83% and 87% of the CIP and European material respectively had T or D cytoplasm types. In general, the CIP breeding programme was more diverse than the European, but not by all that much. Neither set of authors did the calculation, but the Shannon-Wiener diversity indeces were 0.42 for Europe and 0.58 for CIP, for what that’s worth.
Does it matter? Yes. Quite apart from the disadvantages of the resulting increasing genetic uniformity, these cytoplasm types are concidentally associated with male sterility. That makes them difficult to use in breeding.
…we found that CIP’s breeding germplasm as many others worldwide has experienced a genetic bottleneck in terms of cytoplasmic diversity and continuous incorporation of D- and W/c-type cytoplasms due to the unintended and continuous use of cytoplasmic-based male-sterile maternal lineages in its breeding program. Presumably, CIP breeding activity has already been hindered to a certain extent by sterility problems… CIP functions as a source for distributing breeding germplasm worldwide. Our results show that most of the CIP material distributed to developing countries has T- and D-type cytoplasm. Breeders in developing countries may experience breeding constraints imposed by pollen sterility associated with these cytoplasm types.
So it matters, but there’s a way out.
Nonetheless, male-fertile T-type breeding lines must have contributed to alleviate the problem, thus enabling progress for multiple traits in CIP breeding populations.
And also, D-type germplasm is not all bad. Both it and the M-type were positively correlated with late blight resistance, according to the Europe paper.
So, as ever, swings and roundabouts. Crop wild relatives can be really useful, but you have to careful not to get carried away.
Australian Aboriginal agriculture?
Watching a very poignant interview with Bruce Pascoe, an indigenous Australian writer, alerted me to the fact that his most recent book, Dark Emu, which was out last year, is apparently a reconsideration of whether Aboriginal peoples were in fact solely hunter-gatherers. That is what the conventional wisdom holds, or at least held, the last time I checked. I clearly haven’t checked in a while.
Hunter-gatherer societies forage and hunt for food and do not employ agricultural methods or build permanent dwellings… But as I read these early journals, I came across repeated references to people building dams and wells, planting, irrigating and harvesting seed, preserving the surplus and storing it in houses, sheds or secure vessels…and manipulating the landscape.
I’ve only been able to find one academic review of the book online. Is it being ignored by the establishment?
Of plants and their pests
For whatever reason, there was a spate of papers on the coevolution of plants and their pests last week. Or at least I got to hear about them last week.
The one that got the most attention by the popular press — well, actually, the only one that got any attention by the popular press — was a study comparing changes in glucosinolates in the brassica family with speciation in the Pieridae butterflies, whose caterpillars feed on these plants. Glucosinolates give wasabi and mustard their zing (hence the press interest), but are deadly to insects, which is why they evolved in the first place. Each major innovation in the chemistry of glucosinolates since they first arose in the brassicas at the K-T boundary is correlated, the authors found, with a burst of diversification in detoxification mechanisms among the insects at which they were aimed.
The other two studies don’t delve quite so deeply back into evolutionary time, focusing on the role of domestication. The first looked at populations of the green peach aphid (Myzus persicae) growing on a diversity of both crops and their wild relatives. The authors found that aphid populations on domesticated species were more genetically diverse, but evolved more slowly, because selection was less strong and populations larger, weakening the effect of genetic drift. Applying this result to the brassica-butterfly model would suggest that the strength of the association between glucosinolate and butterfly diversity should decrease for the domesticated brassicas compared to the wild ones, but I’m not sure this was looked at in that study.
The third paper investigated the apple’s fungal pathogen Venturia inaequalis. The dispersal characteristics of dozens of strains collected on both domesticated and wild apples in Kazakhstan were compared. The authors found that apple domestication has led to enhanced colonization capacity by the pathogen: strains from orchards have more, bigger spores. Seems to me that’s somewhat contradictory to the aphid example.
The relationship between plants and their pests is, well, complicated.
Brainfood: Nigerian fruit & veg, South African veggies, Veggies in home gardens, Standardizing phenotyping, Potato diversity, Triploid chamomile, Chocolate chip, Fungi & oils, Melon diversity, CC and grasslands
- Promoting food security and enhancing Nigeria’s small farmers’ income through value-added processing of lesser-known and under-utilized indigenous fruits and vegetables. It’s the infrastructure, stupid.
- The role of wild vegetables in household food security in South Africa: A review. No, it’s the information, stupid.
- Indigenous wild food plants in home gardens: improving health and income — with the assistance of agricultural extension. Nope, it’s the extension, stupid.
- Towards recommendations for metadata and data handling in plant phenotyping. It’s the standardization, stupid.
- Cytoplasmic diversity in potato breeding: case study from the International Potato Center. It’s a genetic bottleneck, stupid.
- Towards breeding of triploid chamomile (Matricaria recutita L.) — Ploidy variation within German chamomile of various origins. It’s the triploids, stupid.
- Making a chocolate chip: development and evaluation of a 6K SNP array for Theobroma cacao. Oh, very clever, now everybody and their uncle will be able to breed cacao, stupid.
- Arbuscular mycorrhiza differentially affects synthesis of essential oils in coriander and dill. It’s not just genetics, stupid.
- Comparative transcriptional profiling analysis of developing melon (Cucumis melo L.) fruit from climacteric and non-climacteric varieties. It’s the sugar metabolism, stupid.
- Climate-driven diversity loss in a grassland community. It’s the increasing aridity, stupid.