Category: Wild relatives

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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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Inter situs conservation unveiled

Following our recent exchange of views on assisted migration, Prof. Vernon Heywood has alerted me to the fact that the latest issue of BGjournal (Vol. 6, No. 1, January 2009) is devoted to ecological restoration.

Amongst the many interesting articles is one on inter situ [sic] conservation which is an issue related to assisted migration. It deals with reintroduction of species to locations outside the current range but within the recent past range of the species unlike assisted migration which deals with the introduction of species (or communities) to areas not at present within their ‘native’ ranges. Both are forms of human-aided translocation of species. On a pedantic note, the correct term for the former should be inter situs not inter situ. I suppose that assisted migration could be viewed as anticipated or predictive inter situs conservation but I would not advocate using such terms.

Another article (by Dixon & Sharrock) in the same issue is on botanic gardens and restoration and includes a Box on the potential and problems of assisted migration.

Perhaps the biggest problem with assisted migration is that while we have various bioclimatic models for predicting species’ distributions under different climates we are not really able to incorporate habitat availability or predict it independently of niche models. We need to know what the habitat and species assemblage (“ecosystem”) are likely to be in the future that we are planning to introduce species into!

It’s not online on the BCGI website yet, but it soon will be.

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Good news for wheat

Two studies out in the past week in Science are going to help wheat breeders fight diseases. One identified a DNA sequence — for a product known as the Lr34 transporter protein — which seems to confer protection against no fewer than three fungal diseases. And another study showed that a (different) DNA segment (called Yr36), which had previously been introgressed into durum wheat from wild emmer, also conferred rust resistance in the field (via). Gene discovery strikes again.

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Using wild rice to fight pests

Well, maybe. The article in The Monitor is a bit confused. Yes, there are wild rices in Uganda. I know because I was (marginally) involved in the 1997 Sida-IRRI project which collected wild Oryza in Eastern and Southern Africa. The material has been conserved since then in the National Genetic Plant Resources Centre for Crops in Entebbe, and has now been evaluated — successfully, it would seem — for resistance to Yellow Mottle Virus. Which is great. But the crossing with cultivated rice has not started in Uganda, I don’t think. The crosses that are alluded to in the article seem rather to have been between Asian rice and cultivated African rice (Oryza glaberrima), presumably aiming to replicate the success of Nerica in West Africa. Anyway, good luck to Drs John Mulumba Wasswa and Jimmy Lamo with the breeding programme.