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Clark S.L.,U.S. Department of Agriculture | Schlarbaum S.E.,University of Tennessee at Knoxville | Saxton A.M.,University of Tennessee at Knoxville | Hebard F.V.,American Chestnut Foundation
Forestry | Year: 2012

The American chestnut [Castanea dentata (Marsh.) Borkh.] was decimated by an exotic fungus [Cryphonectria parasitica (Murr.) Barr] in the early 1900s. Breeding efforts with American and Chinese chestnuts (C. mollissima Blume) produced putatively blight-resistant progeny (BC3F3) in 2007. We compared two nut size classes for differences in seedling quality of bare-root stock grown in commercial nurseries. We compared the BC 3F3 generation to parental species and other generations. Nuts in the large size class produced taller trees than nuts in the small size class, but sizing nuts prior to sowing did not reduce variability in nursery seedling size. Results indicate that overall seedling quality could be improved by culling small nuts, but seedling uniformity would only be improved by culling seedlings before planting. We recommend refinement of restoration efforts to match seedling size to site type and planting goals. BC3F3 chestnuts differed from Chinese chestnuts in 67 of tests, and were different than American chestnuts in half the tests, indicating not all American traits were recovered in this early phase of seedling development. Family differences within the BC3F3 generation were most apparent for mean nut weight, and only one BC3F3 family differed from other BC3F3 families in seedling growth characteristics. © 2012 Institute of Chartered Foresters. All rights reserved. Source


Sisco P.H.,American Chestnut Foundation | Neel T.C.,Tennessee Chapter of the American Chestnut Foundation | Craddock J.H.,University of Tennessee at Chattanooga | Shaw J.,University of Tennessee at Chattanooga
Acta Horticulturae | Year: 2014

Cytoplasmic male sterility (CMS) is present in progeny of interspecific crosses between American and Asian Castanea species. F1 progeny of C. dentata as female C. mollissima as male are almost always male sterile, whereas F1 progeny of the reciprocal cross are male fertile. There are, however, exceptions to this general rule. These exceptional C. dentata C. mollissima trees are male fertile rather than male sterile. Analysis of the trnV-ndhC region of chloroplast DNA (cpDNA) of both male sterile and male fertile F1 hybrids of C. dentata C. mollissima demonstrated that male sterility was correlated with the American chestnut D chloroplast haplotype while fertile hybrids of the same genotype had either the P or M chloroplast haplotype. This variation in male fertility in hybrids of C. dentata C. mollissima may be caused by the interaction of nuclear genes from C. mollissima with genes encoded in the mitochondria inherited from C. dentata, because in other species CMS has been found to be associated with variations in mtDNA. This assumes that the mitochondrial DNA (mtDNA) haplotype associated with D chloroplasts is different from the mitochondrial haplotype(s) associated with the P and M chloroplasts. This is an example of the effect of cytoplasmic haplotype on a whole tree phenotype. Source


Fei S.,Purdue University | Liang L.,University of Kentucky | Paillet F.L.,University of Arkansas | Steiner K.C.,Pennsylvania State University | And 4 more authors.
Diversity and Distributions | Year: 2012

Aim Chestnuts (Castanea spp.) are ecologically and economically important species. We studied the general biology, distribution and climatic limits of seven chestnut species from around the world. We provided climatic matching of Asiatic species to North America to assist the range-wide restoration of American chestnut [C. dentata (Marsh.) Borkh.] by incorporating blight-resistant genes from Asiatic species. Location North America, Europe and East Asia. Methods General chestnut biology was reviewed on the basis of published literature and field observations. Chestnut distributions were established using published range maps and literature. Climatic constraints were analysed for the northern and southern distribution limits and the entire range for each species using principal component analysis (PCA) of fourteen bioclimatic variables. Climatic envelope matching was performed for three Chinese species using Maxent modelling to predict corresponding suitable climate zones for those species in North America. Results Chestnuts are primarily distributed in the warm-temperate and subtropical zones in the northern hemisphere. PCA results revealed that thermal gradient was the primary control of chestnut distribution. Climatic spaces of different species overlap with one another to different degrees, but strong similarities are shown especially between Chinese species and American species. Climatic envelope matching suggested that large areas in eastern North America have a favourable climate for Chinese species. Main conclusions The general biological traits and climatic limits of the seven chestnut species are very similar. The predictions of Chinese species climatic range corresponded with most of the historical American chestnut range. Thus, a regionally adapted, blight-resistant, introgressed hybrid American chestnut appears feasible if a sufficiently diverse array of Chinese chestnut germplasm is used as a source of blight resistance. Our study provided a between-continent climate matching approach to facilitate the range-wide species restoration, which can be readily applied in planning the restoration of other threatened or endangered species. © 2012 Blackwell Publishing Ltd. Source


The "then boundless chestnut woods" Thoreau wrote about in Walden once grew throughout the Appalachian mountains. They provided habitat and a mast crop for wildlife, a nutritious nut crop for humans and a source of valuable timber. Because of their rapid growth rate and rot-resistant wood, they also have significant potential for carbon sequestration, important in these days of climate change. The species has a sad story to tell. Of the estimated four billion American chestnut trees that once grew from Maine to Georgia, only a remnant survive today. The species was nearly wiped out by chestnut blight, a devastating disease caused by the exotic fungal pathogen Cryphonectria parasitica. This fungus was accidentally introduced into the United States over a century ago as people began to import Asian species of chestnut. It reduced the American chestnut from the dominant canopy species in the eastern forests to little more than a rare shrub. After battling the blight for more than a century, researchers are using the modern tools of breeding, bio-control methods that rely on a virus that inhibits the growth of the infecting fungus, and direct genetic modification to return the American chestnut to its keystone position in our forests. To restore this beloved tree, we will need every tool available. It's taken 26 years of research involving a team of more than 100 university scientists and students here at the not-for-profit American Chestnut Research and Restoration Project, but we've finally developed a nonpatented, blight-resistant American chestnut tree. My research partner, Dr. Chuck Maynard, and I work with a team at the SUNY College of Environmental Science and Forestry (ESF) that includes high school students, undergraduate and graduate students, postdoctoral fellows, colleagues from other institutions and volunteers. Our efforts focus on direct genetic modification, or genetic engineering, as a way to bring back the American chestnut. We've tested more than 30 genes from different plant species that could potentially enhance blight resistance. To date, a gene from bread wheat has proven most effective at protecting the tree from the fungus-caused blight. This wheat gene produces an enzyme called oxalate oxidase (OxO), which detoxifies the oxalate that the fungus uses to form deadly cankers on the stems. This common defense enzyme is found in all grain crops as well as in bananas, strawberries, peanuts and other familiar foods consumed daily by billions of humans and animals, and it's unrelated to gluten proteins. We've added the OxO gene (and a marker gene to help us ensure the resistance-enhancing gene is present) to the chestnut genome, which contains around 40,000 other genes. This is a minuscule alteration compared to the products of many traditional breeding methods. Consider the techniques of species hybridization, in which tens of thousands of genes are added, and mutational breeding, in which unknown mutations are induced. Genetic engineering allows us to produce a blight-resistant American chestnut that's genetically over 99.999 percent identical to wild-type American chestnuts. For some, this raises a question: isn't moving genes between species unnatural? In short: no. Such movement has been essential to the evolution of all species. Researchers are discovering that horizontal (between-species) gene transfer happens in nature and even in our own bodies. In fact, the same organism (Agrobacterium) that we use to move blight-resistance genes into chestnuts has also permanently modified other plants in the wild. For example, all the sweet potato varieties on the market today were genetically engineered by this bacterium around 8,000 years ago. There is another logical question: what about unintended consequences? Of course undefined questions are impossible to answer, but logically the method producing the smallest changes to the plant should have the fewest unintended consequences. We have not observed nontarget transgene effects – that is, changes that we didn't intend – on our trees or on other organisms that interact with our trees, for example with beneficial fungi. And at any rate, unintended consequences aren't constrained to the genetics lab. Chestnut growers have seen unintended consequences resulting from their hybrid breeding of chestnuts. One example is the internal kernel breakdown (IKB) seen in chestnut hybridization, caused by crossing a male sterile European/Japanese hybrid ("Colossal") with Chinese chestnut. By mixing tens of thousands of genes with unknown interactions through traditional breeding, occasionally you get incompatible combinations or induced mutations that can lead to unintended outcomes like IKB or male sterility. One of the key advantages of genetic engineering is that it's far less disruptive to the original chestnut genome – and thus to its ecologically important characteristics. The trees remain more true to form with less chance of unforeseen and unwanted side effects. Once these genes are inserted, they become a normal part of the tree's genome and are inherited just like any other gene. They have no more chance of moving to other species than do any of the approximately 40,000 genes already in chestnut. Next steps for the blight-resistant American chestnut One of the challenges of genetic engineering that is not faced by any other methods of genetic modification also serves as a safeguard. We must shepherd these trees through federal regulatory review by the U.S. Department of Agriculture, the Environmental Protection Agency and the Food and Drug Administration. Our plan is to submit these applications as we finish collecting the necessary data; we expect the process to take three to five years. Once we receive (anticipated) approval, we will quickly make the trees available to the public. This project is unique because it is the first to seek approval of a transgenic plant to help save a species and restore a forest's ecology. Our forests face many challenges today from exotic pests and pathogens such as Emerald Ash Borer, Helmlock Wooly Adelgid, Sudden Oak Death, Dutch Elm Disease, and many more. The American chestnut can serve as a model system for protecting our forest's health. Direct genetic modification will likely not be used in isolation. Integration might improve the outcomes of both the conventional hybrid/backcross breeding program of the American Chestnut Foundation and our genetic engineering program. Allowing crosses between the best trees from both programs will allow gene stacking – having multiple and diverse resistance genes in a single tree – with each working in a different way to stop the blight. This would significantly decrease the chances that the blight could ever overcome the resistance. The two programs working together would also allow the addition of resistance genes for other important pests, such as Phytophthora, which causes a serious root rot in the southern part of the chestnut range. And combining methods increases the chances that the resistance will be long-lasting and reliable, which is very important for a tree that in good health can live for centuries. A unique aspect of the genetically engineered American chestnut trees is their ability to rescue the genetic diversity in the small surviving population of American chestnut trees. When we cross our blight-resistant transgenic trees to these surviving "mother" trees, directly in the wild or from nuts gathered from them and grown in orchards, we're helping preserve the remaining wild genes. Half the resulting offspring will be fully blight-resistant, while also containing half the genes from the mother tree. By making these crosses, the restoration trees will be ecologically adapted to the diverse environments in which they'll grow. These trees could also be used to boost the genetic diversity of the hybrid/backcross breeding program, or used directly for restoration and left to fend for themselves, allowing natural selection to make the final determination of the effectiveness of our efforts. The American chestnut was one of the most important hardwood tree species in the eastern forests of North America, and it can be again. This tiny change in the genome will hopefully be a huge step toward putting the American chestnut on a path to recovery. More information: Douglass F. Jacobs et al. Aboveground carbon biomass of plantation-grown American chestnut (Castanea dentata) in absence of blight, Forest Ecology and Management (2009). DOI: 10.1016/j.foreco.2009.04.014


News Article | January 17, 2012
Site: techcrunch.com

Good news, gadget hounds! The new “try before you buy” subscription service called YBUY is exiting its public beta, backed by $750,000 in seed funding. The concept is simple, and should have major appeal for the gadget-obsessed: for just $24.95 per month, you can test drive the latest electronics, home and kitchen gadgets for 30 days before deciding to purchase or return the items. At launch, the site is serving up highly sought-after gadgets like the iPad 2, Dyson heaters, Jawbone headsets, iRobot Roombas and more. The gadgets are shipped to customers for free, and the package also includes a return label for free shipping on the way back to YBUY if you decide you’re not interested in purchasing. However, if find that you can’t bear to part with your shiny new iPad 2 (as is the exception, of course), you can proceed to purchase the item minus the $24.95 you already paid. The company says it will also discount items under regular retail prices to make buying through YBUY more compelling. This isn’t always the case, though. For example, YBUY lists the iPad 2 for $499.99 and the Jawbone Jambox for $199.99 – those are the going rates. Explains CEO Stephen Svajian, “for manufacturers, we provide an easy-to-use sales channel that allows them to offer refurbished products to consumers without the added cost of marketing and sales.” In other words, not all the gadgets are the cheaper (but manufacturer-certified) refurbs. The Manhattan Beach, Ca.-based startup was founded by serial entrepreneur Stephen Svajian and Kevin Wall, a Managing Partner at Craton Equity Partners and CEO of Live Earth, among other things. The company’s $750,000 in seed funding comes from the founders themselves and other angels.

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