Category: Genetic diversity

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A tale of two apple collections

I’ve already nibbled today’s piece in the Guardian about the UK’s National Fruit Collection at Brogdale, a “typical British story of managerial confusion and government ineptitude,” ((Be sure to read the comments, one of which links to other sources of information on the situation at Brogdale.)) but I couldn’t resist pointing out the contrast with the US apple collection at Geneva in New York, about which I also blogged recently. It does seem like they order these things better across the pond.

Coincidentally, there was also an article today about the diversity of American apples. Here it is in numbers: 2,500 named varieties grown in the country, 100 commercially, 15 accounting for 90% of the harvest.

The dizzying array today might have shocked early Americans. Just a half-dozen wild crab apple varieties awaited British colonists arriving in America in the 17th century. Thousands of hillside orchards soon were planted with the progeny of favored European varieties… like Maiden Blush, Western Beauty, Chenango Strawberry, Roxbury Russet and Westfield Seek No Further.
…

“There were some real jewels among them with great flavors, rich with juices and unusual aromas,” said Tom Burford, an author, lecturer, orchard and nursery consultant from Lynchburg, Va. Burford has been dubbed “Professor Apple” for his extensive work rediscovering antique varieties previously believed extinct.

Is there a British “Professor Apple” out there who will save Brogdale? Or maybe the situation is not as bad as the Guardian piece made out? If you know, drop us a line.

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Wheat disease genes

Fusarium graminearum is the fungus that causes Fusarium head blight, a serious disease of wheat and barley. FHB infects the flowers and makes itself at home in the seed, which ends up shrunken and white and loaded with toxins that can have a harmful effect on people and animals that eat the grain. A study just published in Science decoded the DNA sequence of the fungus and sheds some light on its virulence and variability ((The Fusarium graminearum Genome Reveals a Link Between Localized Polymorphism and Pathogen Specialization. Science: 317:1400 – 1402 DOI: 10.1126/science.1143708)).

The sequence of one strain is interesting enough, but the surprises emerged when the researchers, led by Corby Kistler at the University of Minnesota, compared two different strains. There were more than 10,000 differences between the two sequences. Those differences, however, were not spread evenly along the DNA; more than half of the differences were concentrated in just one eighth of the sequence.

So some regions of the genome are much less stable than others. And what genes are in those regions? Mostly ones concerned with infection and virulence, among them the genes for compounds that dissolve the host cell walls and others that digest host molecules so that the fungus can make use of them.

Just why the variability in Fusarium graminearum is concentrated in some areas of the DNA is not yet clear. These areas seem to be hotspots for recombination, which shuffles the DNA during sexual reproduction and so promotes diversity, but this particular fungus doesn’t go in for sexual reproduction all that often. A mystery, then, but one that may still yield new approaches to breeding resistant wheat and barley and perhaps to new kinds of treatment.

You may remember that a joint team of Israeli and US researchers recently reported that a wild relative of wheat, Sharon Goatgrass (Aegilops sharonensis), is loaded with resistance genes that protect it against seven of the most important fungal diseases of wheat. Alas, none of the samples tested was resistant to Fusarium head blight. How about some other wild relative species, though? We shall see.

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I say kumato

The FreshPlaza piece on the kumato is not very long. But it does manage to squeeze in a lot of interesting information. The kumato is a tomato that ripens from green to dark brown. It is the result of a conventional breeding programme which involved a wild species. And it is just coming up to its first harvest in Australia. This definitely deserved more investigation.

There’s no doubt it looks pretty extraordinary. But the most intriguing thing about the kumato is that the wild species involved in its development may be from the Galapagos.

Now, Lycopersicon cheesmaniae from the Galapagos Islands has been used to breed dark orange tomatoes before, though it does not have a dark brown skin like the kumato. ((This species was actually published as L. cheesmanii, after Evelyn Cheesman, but that was incorrect, as the Latinists among us will know, as Ms Cheesman was a woman and the specific epithet therefore requires a feminine ending.)) Check out this excerpt from an article celebrating the late great tomato geneticist and explorer Prof. Charles M. Rick in 1997, five years before his death:

Rick’s research led him on 15 genetic scavenger hunts to Andean South America, the homeland of the tomato, where he hunted for wild tomato varieties carrying useful genes. Among his discoveries were wild tomatoes growing near the tidelands of the Galapagos Islands, despite salty sprays that would have stunted or killed a domestic tomato plant.

Or again:

An excellent lecturer, Rick was much sought after by universities who valued both his rigorous science and his humor and flair for storytelling. A perennial favorite involved his frustrations in trying to germinate wild tomato seeds collected from the Galapagos Islands. The emerging mystery of how the plants reproduce in the wild was only resolved after the seeds were “processed” by passing through the digestive track of a Galapagos tortoise, resulting in vigorous seedlings.

The kumato should actually be the Kumato©. It was bred by Syngenta, and first released in the UK in about 2004, I think. But the Roguelands Heirloom Vegetable Seeds Company also has 40 different dark brown to black-skinned varieties in its collection, and says black tomato varieties first appeared in the 19th century in Ukraine.