| Slide 2 |
| Backcrossing More than one American chestnut line also is needed, also to avoid inbreeding, when B3s are intercrossed with each other. |
| Slide 4 |
| Sources of Blight Resistance |
| Our primary source of blight resistance is Chinese chestnut, because that was identified as the most resistant species by the USDA in the 1930s. No resistance was known in American chestnut until the 1980s. We also have a few crosses with Japanese and European chestnut. C. henryi and C. sequinii also may have individuals with high resistance, based on recent observations in China. | |
| Number of Trees at Meadowview in 2008 |
| TACF Meadowview Nut Harvest 2008 |
| Slide 8 |
| Selection for Recurrent Type |
| Trichome density and type | |
| Stipule size and shape | |
| Leaf shape | |
| Tooth shape | |
| Lenticel density, size and color | |
| Stem color | |
| Form | |
| Time of leaf emergence | |
| Vigor | |
| Slide 10 |
| Slide 11 |
| "Table 1." |
| Table 1. Number of trees in canker size classes in 1993. | |
| Cross Type Size Class (cm) _________ | |
| 1.0-2.6 2.6-4.2 4.2-5.8 5.8-7.4 7.4-9.0 9.0-10.6 10.6- | |
| ______________________________________________________________________________ | |
| American 3 5 2 | |
| F1 Nanking 2 4 3 | |
| Seedling Chinese 2 7 3 | |
| Meiling Chinese 1 2 2 | |
| Nanking Chinese 3 2 | |
| F2 Mahogany 0 5 23 48 48 29 15 | |
| B1-F2 ClapperxGraves 4 25 84 116 112 54 4 | |
| ______________________________________________________________________________ | |
| Table 2. Number of trees in canker size classes in 2003. | |
| Cross Type Size Class (cm) __________ | |
| 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0 5.0-6.0 6.0-7.0 7.0-8.0 | |
| ________________________________________________________________________________ | |
| American 4 2 2 2 1 | |
| F1 Nanking 1 2 3 1 | |
| Chinese 3 3 3 6 | |
| B2-F2 Clapper 3 11 15 37 16 12 3 | |
| B2-F2 Mahogany 3 11 21 31 14 14 1 | |
| ________________________________________________________________________________ |
| Chestnut Blight Resistance Rating Scheme |
| Slide 14 |
| Blight-resistant Chinese to
American B1-F2, ÔClapperÕ x ÔGraves.Õ Obtaining trees like this suggests it should be possible to backcross the blight resistance of Chinese into American chestnut. |
| Slide 16 |