Chestnut Blight

Chestnut Blight - ANTH/PATH 2010 Plants People and...

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ANTH/PATH 2010 Plants People and Pathogens CHESTNUT BLIGHT and the Plant Quarantine act: American Chestnut - Castaneae dentata NC 1910 IMPORTANCE Before 1900 Am. chestnut was most dominant hardwood tree eastern US ± 25% of trees in Appalachian forests ± chestnut stands spread from ME to FL
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± trees reached 83 ft tall; 27’’ diam., 103 yrs old ± second to oak in usefulness and durability ± wood had beautiful grain ¾ excellent for house trim, furniture and flooring ± resistant to dry rot and weathering ± (branch-free for 50 ft ¾ well suited for telephone poles, rail road ties, fence posts and rails. ± tannins were used for curing leather ± humans and animals (wildlife) consumed nuts ± popular shade tree in yards and public parks.
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Am. Chestnut (~4 billion trees) was decimated by chestnut blight - Cryphonectria parasitica in a 30-40yr period 1900/08 - 1940 Disease cycle
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Fungal spores (conidia/ascospores) produced in the spring Rain, insects and animals disseminate fungus to wounds in woody tissues - spores land on freshly wounded trees, penetrate and infect Symptoms/signs /
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- sunken or swollen cankers form in the bark - all portions of tree above canker die.
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- Infected stump may survive and sprout a sapling. Sapling becomes infected and dies. Management 1) Chinese and Japanese chestnuts have some resistance - breeding programs seek to develop resistance. o Programs take a long time 2) Hypovirulence - viruses that naturally attack fungus ± chestnut populations appeared to be recovering from blight; ± fungal strains on those trees were infected with a hypovirus ± inoculating trees with a weakened form of the fungus ± did not work in practice o genetic differences between fungus strains variants of the hypovirus.
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3) Genetically modified resistance to CB ± use transgenics to place R genes from plants like wheat into American chestnuts o at this point only a few transgenic chestnut trees exist History of CB & Plant quarantine act 1904: American chestnut trees dying in Bronx Zoological gardens NY 1906: cause of death - Chestnut blight Where did the pathogen originate - - Asian Chestnut species resistant to CB In 19 th century US nurserymen imported Asian chestnut trees 1882: 1,000 grafted Japanese Chestnut trees into NJ 1886: 10,000 Japanese chestnut trees in CA 1900/1902: Chinese chestnuts ( Castanea mollisima ) planted in MD - many opportunities for pathogen introduction 1906: CB was observed in NJ, MD VA 1907: CB reached NY - disease spread at ~ 24 miles per year 1950: all mature American chestnuts in US were infected with CB
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1907: Haven Metcalf - born 1875 in ME chief USDA chestnut blight researcher - CB received a lot of media attention 1909 Metcalf reported on biology of CB and recommended: ± inspection of nursery stock ± eradication of infected trees ± quarantines - establishment of a CB-free buffer zone o origin of fungus was not known
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o not sure if quarantines would work
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This note was uploaded on 11/01/2010 for the course PATH 2010 taught by Professor Walcott during the Fall '10 term at UGA.

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Chestnut Blight - ANTH/PATH 2010 Plants People and...

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