Reviewing the use and usefulness of cereal landraces

From Eliseu Bettencourt, one of the authors of the paper concerned.

The paper “Cereal landraces for sustainable agriculture. A review” was recently made available on-line at Agronomy for Sustainable Development, though behind a paywall. The paper version will be published soon.

The paper is co-authored by eighteen authors pulling together diverse backgrounds and expertises.

The review addresses the current status and prospects for cereals landraces in the context of sustainable agriculture, discussing the place of landraces in the origin of modern cereal crops and breeding of elite cereal cultivars, the importance of on-farm and ex situ diversity conservation; how modern genotyping approaches can help both conservation and exploitation; the importance of different phenotyping approaches; and whether legal issues associated with landrace marketing and utilisation need addressing.

The paper also deals with the current status and potential for the improved deployment and exploitation of landraces, and incorporation of their positive qualities into new cultivars or populations for more sustainable agricultural production. In particular, their potential as sources of novel disease and abiotic stress resistance genes or combination of genes if deployed appropriately, of phytonutrients accompanied with optimal micronutrient concentrations which can help alleviate aging-related and chronic diseases, and of nutrient use efficiency traits.

The paper is structured in 12 chapters, namely: Introduction; History of cereal landraces; Diversity and germplasm collections; Genebanks and conservation of cereal landraces; Genotyping and phenotyping; Nutrient uptake and utilisation; Nutrition and quality; Biotic and abiotic stress resistance and tolerance; Breeding: conversion of landraces into modern cultivars; Participatory breeding; Legal issues; Conclusions. The paper also counts with an extensive list of bibliographic sources.

The main findings of the paper can be summarised as: A lot of recent research effort has gone into collecting, organising, studying and analysing cereal landraces with a primary goal being to incorporate their positive qualities in new cultivars or populations for a more sustainable agricultural production, particularly in response to recent climate changes.

A major part of this valuable landrace diversity is conserved in the world’s genebanks network and should be exploited systematically for traits such as quality and specific adaptations to stress environments. However, the available genetic variation in adaptive responses to soil and climatic conditions conserved in landraces is little understood, and even less used. More uniform and user-friendly documentation about collection and characterisation of landraces, either morphologically or with molecular tools, is needed to access this variation more effectively. Genebanks should aim at adopting a common concept of landraces and plan special inventories for them. The level of diversity should be monitored during their conservation so that the original level of variation is maintained. More studies are needed in order to investigate if their long-term maintenance by farmers resulted in increasing genetic variation.

New high-throughput genotyping platforms and phenotyping data in common databases will enable powerful association genetic approaches to be used for improvement and direct deployment of landrace resources.

The renewed focus on cereal landraces for breeding purposes is also a response to some negative consequences of modern agriculture and conventional breeding, such as the liberal use of high inputs, the loss of genetic diversity and the stagnation of yields in less favourable areas.

Further enhancement of productivity and stability is achieved through practicing “non-stop selection” within landraces across the marginal production environments, to exploit the constantly released by the genome useful adaptive variation.

The review highlights the value of landraces as resources for the future sustainability of cereal crop production, the methods to enhance their genetic makeup and avoid seed degradation and emphasises the level of co-ordination and resourcing needed to realise the great potential of cereal landraces.

Nibbles: Olives, Livestock, Data, Data sharing, Cheese paring, Book, tanzania

Invasiveness and extinction revisited

If you’ve been following (listening to?) our tweets ((I never thought I’d ever write that, but time and the social web wait for no-one.)) you might have seen this enigmatic little gem:

Population genetic diversity influences colonization success. K. M. CRAWFORD. Molecular Ecology: http://goo.gl/JFHh

And, possibly, ignored it. It must have registered at some level though, because when I saw Inbreeding bad for invasives too at C.J.A. Bradshaw’s blog Conservationbytes.com I thought, “Hmmn, I wonder if that’s the thing we tweeted”. ((Which gives me the opportunity to remind you that we don’t tweet everything we write about here, nor do we write here about everything we tweet.)) And it was. Bradshaw does a great job of explaining how it is that reduced genetic diversity contributes not only to a population’s risk of extinction, but also to its ability to invade new habitats.

Crawford & Whitney measured greater population-level seedling emergence rates, biomass production, flowering duration and reproduction in high-diversity populations compared to lower-diversity ones. Maintain a high genetic diversity and your invasive species has a much higher potential to colonise a novel environment and spread throughout it.

Of course, this is related to propagule pressure because the more individuals that invade/are introduced the more times, the higher the likelihood that different genomes will be introduced as well.

So far the experimental evidence comes only from Arabidopsis thaliana, the white rat of the plant biologist. But I’d be willing to bet that if you could measure such a thing as invasiveness and persistence for crop varieties, where people, rather than nature, determine how many propagules survive and spread, the ones that are both widespread and long-lasting are also the ones with the most genetic diversity.

Locating agricultural origins in Mexico and Italy

I know that domestication is not an event, but a process. I know that most crops and livestock were probably domesticated more than once, in more than one area. I know all this, but I’m still a sucker for papers that come up with specific times and places for the origin of agriculture. Papers such as Daniel Zizumbo-Villarreal and Patricia Colunga-GarcíaMarín‘s in the latest GRACE:

Sympatric distribution of the putative wild ancestral populations of maize, beans and squash indicate the extreme northwest Balsas-Jalisco region as a possible locus of domestication.

The paper is a review. It synthesizes a host of paleoecological, archaeobotanical and molecular data. Meanwhile, another paper, this time in the Journal of Archaeological Science, applies matrix mathematics to a somewhat different, though related, problem: the arrival of wheat in Italy. The authors looked at a selection of old emmer landraces from all around Italy stored in the German and ICARDA genebanks. ((The question of why they did not obtain material from an Italian genebank is one that I am loath to explore, for fear of what I might find.)) They developed a matrix of genetic distances among these based on microsatellite data. They then calculated matrices of geographical distances among the landraces based on different putative places of arrival of the crop around the coast of Italy. The two matrices showed the closest correlations for arrival sites located in northern Puglia, the heel of Italy. That corresponds with where the earliest Neolithic sites are found.

Now, I wonder, when will someone apply this method to maize, beans and squash molecular data and test mathematically Zizumbo-Villarreal and Colunga-GarcíaMarín more “qualitative” inferences?