Category: Breeding

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AVRDC’s treasure trove of diversity

I was recently at AVRDC headquarters in Taiwan and was quite taken with their demonstration garden. (Among other things. The genebank operation is also impressive, and recovering from a recent unfortunate setback.) It’s a wonderful display of both vegetable diversity and cultivation systems. I was going to blog about it, but then life intervened, or at least work did. Anyway, the latest issue of AVRDC’s newsletter has a piece on the garden, and they have kindly agreed for us to reprint it here, as the newsletter itself is not available online. Which kinda gets me off the hook. The photographs are mine. The following text (and this post’s title) are courtesy of AVRDC.

Although there are thousands of plants people can consume, humanity relies on only a relative handful for food. Indigenous vegetables — whether semi-wild or domesticated — can greatly expand the menu. Grown primarily in their centers of origin or introduced in a given area, indigenous or traditional vegetables provide food in times of scarcity for the world’s poorest people, yet these hardy, nutritious species often are underutilized.

A welcoming sign
AVRDC — The World Vegetable Center — aims to promote production and consumption of indigenous vegetables, and the Center’s Demonstration Garden showcases different species to create awareness and encourage adoption. In the first of a two-part article, Jenny Huang, a public relations and partnership consultant with AVRDC, visits the garden to see what’s growing.

What began in 2001 as an experimental field on the grounds of the AVRDC headquarters campus in Shanhua, Taiwan has blossomed into a 0.63-hectare living example of the mission and work of AVRDC — The World Vegetable Center.

“The Demonstration Garden was designed as an observation plot for indigenous vegetables when we got the project from the Taiwan Council of Agriculture in the beginning,” said Mandy Lin, an assistant specialist in AVRDC Global Technology Dissemination. After 10 years of development, more than 60 different species of indigenous vegetables are cultivated in 200 plots of various sizes and shapes to showcase the special qualities of each species and promote their wider use. The range of species grown also maintains visual interest as the seasons change.

The indigenous vegetables in the garden were selected for three significant characteristics—ease of cultivation (low input), nutritional quality, and resistance to pests and diseases. Visitors touring the Demonstration Garden often are surprised by the number and variety of indigenous vegetables, and the different edible parts, from shoots and leaves to pods and seeds. “We want to convey a simple but principal message to every visitor—that a diverse diet including many different vegetables is beneficial to health,” Mandy said.

In July 2008 the Center’s Global Technology Dissemination group expanded the function of the Demonstration Garden to highlight four major mature technologies: low-cost drip irrigation, starter solution, grafting chambers, and protective shelters. Farmers in developing countries can adopt these technologies to increase yields, improve produce quality, and reduce production costs.

Sweet potato varieties

Visitors and AVRDC staff members alike gain new ideas and inspiration as they walk through the garden, enjoy the rich diversity of plants, and see farming technologies in use. As Mandy observed: “You think you are taking care of crops, but in fact they educate you with their beauty and variety.”

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Detoxifying cassava

Strategies that minimize one risk…may augment another risk… Peasant farmers are perfectly conversant with such linkages. The neglect of peasant agriculture by both donors and governments is among the deeper causes of current crises, along with the increasing inequality that deprives them of secure tenure to land and other resources, reducing benefits they can expect to receive from stewardship of these resources.

That comes towards the end of a lengthy, information-dense and closely argued paper on cassava’s domestication, evolution and chemical ecology by Doyle MacKey and others. 1 Coincidentally — or perhaps not — McKey also has a paper out just now on the evolutionary ecology of vegetatively propagated crops in general. 2 But that’s something for a future post, perhaps. Back to cassava.

Well, as I say, there’s a lot of stuff in the paper, but let me focus on a just a couple of things here. Some cassava varieties are high in poisonous cyanogens, requiring laborious and time-consuming processing for detoxification, which is almost exclusively done by women and, according to at least one anthropologist, serves to control them, “by limiting their freedom of action, in male-dominated societies.” So let’s replace those high-cyanogen, “bitter” varieties with low-cyanogen, “sweet” varieties, right?

Well, not so fast. ‘‘Interestingly enough, the women that are the custodians of this crop do not perceive the processing or the toxin to be a problem.’’ Bitter manioc is in fact better for food security for at least three reasons: it is protected against pests; immediate processing deters thieving; and the value added through processing reduces the social obligation to share. Overall, therefore, “processing bitter manioc is viewed as a useful and valorizing activity.”

But there are regular epidemics still in some parts of Africa of the paralytic disease konzo, which is “associated with several weeks of almost exclusive consumption of insufficiently processed bitter cassava.” Surely low-cyanogen varieties would be welcome there?

Again, the authors are dubious. They point out that agronomic practices, in particular careful nutrient management, together with adequate processing and a reasonably protein-rich diet are perfectly sufficient to manage the toxicity problem, and in fact normally do so. It is mainly when socioeconomic stability breaks down that konzo erupts. As they trenchantly put it: “This crop needs peace.” And reasonable rainfall. Drought stress tends to increase cyanogen levels. Plus, “[a]s they face food shortage, people may then take short cuts in processing bitter manioc.” In both cases, new, faster, more efficient detoxification methods will have a bigger impact than sweet varieties, with their greater susceptibility to pests.

In general, cassava is expected to be comparatively little affected by climate change, and is being promoted in some quarters as a “food for the future.” Fair enough, say the authors, but this

…will need to be accompanied by the necessary education for processing, as planting less bitter cultivars appears not to be a solution. Farmers have good reasons for preferring bitter varieties.

Indeed they do. So let me end with another heady quote, again from the concluding section of the paper, a little further on from the quote I started with.

We must have the humility and the broad vision to accept that our science can provide essential pieces, but only pieces, of viable solutions. ‘‘Modern’’ science can work in creative ways with folk knowledge. But no technological fix is a ‘‘magic bullet’’.

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Nibbles: Mangoes, Bees, Personalities, Business, Education, Meeting, Sorghum

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Genebanks shenebanks

Why bother building and maintaining huge robotic genebanks, I hear you ask? They’ll just take over the world and we’ll end up having to deal with the Terminator in a few years’ time, no? Well, as it happens there are two pieces today on the Worldwatch Institute’s blog which explain the reasons. Yassir Islam of HarvestPlus says that researchers are “scour[ing] seed banks to find seeds that contain the desired nutrients and then breed these into popular varieties using conventional methods.” And Cary Fowler of the Global Crop Diversity Trust turns to Ug99:

Where do you suppose scientists are looking for a way to deal with the disease? Just as Professor Borlaug did, they are screening hundreds of varieties of wheat to find one that shows resistance to the disease. Where would we turn if we did not have that diversity available in genebanks?

What more do you need? Oh yeah:

The UN Food and Agriculture Organization (FAO) estimates that a third of all genetic resources for food and agriculture have already been lost in the last 100 years.

Right. But at least it’s an improvement on 75%.

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Unbottling the lentil

ResearchBlogging.orgIt is well known that crops go through a genetic bottleneck at domestication. Due to the founder effect, they typically show a fraction of the genetic diversity found in their wild relatives. Which is bad, but fixable: fixing it is the plant breeder’s job — or part of it anyway. What’s less well known, according to a recent paper on lentils by Willy Erskine and co-authors in GRACE, is that the movement of a crop around the world can also often lead to bottlenecks. 3

Lentil cultivation moved from Afghanistan into the Indo-Gangetic Plain sometime between 7000 and 4000 BC. The authors “reconstructed” this movement by growing random subsets of the ICARDA world lentil collection at two sites, Islamabad and Faisalabad, in Pakistan. Faisalabad is typical of conditions in the Plain, Islamabad is a transitional, mid-altitude environment.

They found that most Afghani accessions did not flower in Islamabad before the local material matured, due to a combination of temperature and photoperiod, the main determinants of flowering in lentils. The few that did were among the most late-flowering in the world. This is probably related to the shift in sowing from winter to spring as lentils moved from their area of origin in lowland SE Turkey and N Syria into the central Asian plateau. The data from Faisalabad in addition showed that every week’s delay in flowering resulted in a 9% loss of yield potential in the lowlands.

So there was strong selection for reduced sensitivity to photoperiod and a return to early flowering as the lentil moved into the Indo-Gangetic Plain, and consequently a genetic bottleneck. 4 But in a way the surprising thing is that there was no cork in the bottle. Where did the genetic variation that allowed adaptation to the Plain come from? The authors note that time to flower in lentils is controlled by both single gene and polygenic systems, and that early flowering is always recessive. Those recessive alleles for early flowering, which may have come from introgression from a wild relative in Afghanistan, must have occasionally come together and been selected for at mid-altitudes, which then “allowed selection for a radically earlier flowering habit as a new adaptive peak for the novel environment of the Indo-Gangetic Plain.”

The challenge is now for breeders to use these insights to broaden the genetic base of the crop in India, where lentil germplasm “is among the least variable among lentil-producing countries for agro-morphological traits … despite its vast area of cultivation there today.”