Rare breeds at risk of disease

BBC News says that “regional breeds of sheep face a heightened risk of disease because of their tendency to remain together in one location”. It is summarising a report from The Sheep Trust, which was founded during the epidemic of Foot and Mouth disease in the United Kingdom in 2001. That’s important.

What the Trust’s report seems to be saying that when there is an outbreak of disease, the regional, heritage, breeds are vulnerable because they are concentrated in a single geographical location. But that does not put them at greater risk of disease. It puts them at greater risk of being culled as part of government’s policy-based response to the disease. If the policy is to slaughter all animals within, say, 5 km of an affected farm, regardless of whether they have the disease or not, then yes, geographical concentration is a threat to the breed. But it isn’t the disease as such that is the threat, it is the policy response. It is even possible that the policy would wipe out flocks that contain genetic resistance.

What’s the answer? Given that regional breeds are interesting precisely because they are adapted to a small region, simply spreading them about might not be much of a solution. Gene-banking? Well, that’s where we came in: The Sheep Trust is an outgrowth of the Heritage Genebank. So what exactly do they want?

“We are strongly recommending that new measures are put in place to protect these important genetic resources now that their vulnerability has been so clearly demonstrated,” says Professor Dianna Bowles OBE, founder and Chair of The Sheep Trust.

No further details are forthcoming. How very frustrating. Maybe all they want is government money for the sheep genebank.

Critically endangered cassava wild relative delays rotting

Here’s something else I learned at this workshop I’m attending on the state of plant genetic resources conservation and use in Latin America:

Dramatically delayed PPD [postharvest physiological deterioration] was found in Manihot walkerae, a wild relative of cassava found in Mexico and USA (state of Texas) (Fregene and Mba 2004). An accession of M. walkerae (MWal 001) was crossed extensively to elite cassava varieties. A single successful genotype was found with delayed PPD. The storage roots of the hybrid remained intact a month after harvest. Backcrosses of this hybrid to elite progenitors of the CIAT cassava gene pools and selfed (S1) populations were made for genetic mapping of the delayed PPD traits.

This came up during a discussion of the importance of collecting and conserving crop wild relatives. I had no idea the Manihot genus went as far north as Texas. Walker’s manioc turns out to be extremely endangered:

Until recently, it was believed that this species was represented in the U. S. by a single plant in the wild, discovered in Hidalgo County in 1990. In 1995, Walker’s manioc was located in three different areas on the Lower Rio Grande National Wildlife Refuge in Starr and Hidalgo Counties.

It is known from only a couple of populations in Mexico. I don’t give much for its chances in the wild. But there is material in the San Antonio Botanical Garden. And some of its genes are now in some cultivated varieties.

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