| "F." |
| F. V. Hebard | |
| Research Farms | |
| American Chestnut | |
| Foundation | |
| Meadowview, VA | |
| Fred@acf.org | |
| www.acffarms.org |
| Co-Authors |
| Bob Paris | |
| William White | |
| Shaun Yarnes | |
| Mila Wilmoth |
| Outline |
| Physiology and Histology | |
| Fungus Pathogenicity | |
| Resistance Tests |
| Physiology and Histology |
| Initial Lesion Formation |
| Physiology and Histology |
| Mycelial fan is means of breakout from initial lesion. |
| Physiology and Histology |
| Mycelial fans advance by physical pressure. |
| Physiology and Histology |
| In American chestnut, mycelial fans form more rapidly, in greater numbers, and grow more quickly than in Chinese chestnut, which is resistant to blight. |
| Physiology and Histology |
| Cells die in advance of hyphae - living cells indicated here by diaphorase activity stained with Nitro-Blue Tetrazolium |
| Physiology and Histology |
| Enzyme activity in initial lesion and lignifying zone - esterase, phenolase, beta-glucosidase |
| Physiology and Histology |
| Canker size dynamics |
| Physiology and Histology |
| Physiology and Histology |
| Ethylene levels near cankers |
| Physiology and Histology |
| Ethylene can be elicited by a low-molecular-weight carboxylic acid from culture filtrates on chestnut bark broth, which is not oxalate. Oxalate does not elicit ethylene. |
| Physiology and Histology |
| Ethylene as measure of colonization; it is elicited more relative to basal levels in American chestnut than Chinese | |||
| Fungus pathogenicity |
| Fungus Pathogenicity |
| Demonstration of statistically significant differences in canker length on American chestnut for virulent isolates of Cryphonectria parasitica |
| Fungus Pathogenicity |
| Unlike on susceptible American chestnut, strain SG2-3 gives qualitatively smaller cankers than Ep155 on trees with intermediate levels of resistance, such as this one. |
| Fungus Pathogenicity |
| Resistance Tests |
| Resistance Tests |
| Mean canker size in Aug & Sept after June Inoculation for various chestnut crosses in a single test |
| Resistance Tests |
| Resistance Tests |
| Resistance Tests - mortality |
| Resistance Tests - mortality |
| Resistance Tests - Qualitative Rating Scheme |
| Small, Medium and Large Cankers |
| Resistance Tests - Qualitative Rating Scheme |
| Resistance Tests |
| In 2004 or 2005, some trees that scored well in 1993 started displaying fairly severe cankers. | ||
| Was resistance breaking down (pathogen mutating)? | ||
| Was the test in error? | ||
| Or was this normal canker development for Chinese chestnut? | ||
| So we went back and rated all the living trees from the 1993 test (and also isolated the blight fungus from cankers). | ||
| Resistance Tests |
| Connecting results from 1993 to tree size and canker severity in 2006. Difficult. |
| Is this basic test of inoculating trees in late spring and rating them that summer to early winter and the following spring capturing all the components of resistance? |
| What about sclerified phelloderm? |
| Sclerified Phelloderm |
| Initial Observation |
| Sclerified Phelloderm |
| Expectations based on hypothesis |
| Sclerified Phelloderm |
| Periderm, the outer skin of bark |
| Sclerified Phelloderm |
| Wound periderm |
| Sclerified Phelloderm |
| Evidence of Sclerification of Phelloderm |
| Sclerified Phelloderm |
| Observing chunks of bark using epifluorescence |
| Sclerified Phelloderm |
| Images of chunks of bark with sclerified periderm |
| Expectation #1 |
| Chinese but not American trees will show sclerification |
| Expectation #2 |
| The presence of sclerified phelloderm will correlate with resistance measurements in backcross trees. |
| Expectation #3 |
| Selection for resistant trees will inadvertently be a selection for sclerification. |
| Sclerified Phelloderm |
| Patterns of inheritance in families where sclerification occurs of | |
| none+incomplete vs. complete |
| Sclerified Phelloderm |
| Future Directions |
| Crew at Meadowview, 2009 |