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Type of Treatment No. of [Symbol: female]'s at Nut set as
time of first expressed in %
pollination of [Symbol: female]'s
at time of
1st pollination ×3
[Symbol: female] parent [Symbol: female] parent
4-4 7-4 4-4 7-4
(J×A) (J×JA) (J×A) (J×JA)
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Normal emasculation 39 17 29.1 13.7
Only unisexual catkins removed 23 19 14.5 0.0
Not emasculated, but pollinated 28 18 25.0 3.7
Not emasculated, }
not pollinated } Control 28 25 1.2 0.0
Not bagged, branches tagged,
open pollinated 26 23 44.9 17.4
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Bagging apparently was partly injurious on these two trees and caused some decrease in nut yield. There is, however, no evidence that emasculation in itself causes a decreased nut yield, rather it appears to be somewhat beneficial if we are to judge from the results of this experiment. At least, one would be justified in concluding that any harmful effect is negligible. Completely emasculated flowers yielded 29.1 and 13.7 per cent as compared to 14.5 and 0.0 per cent where only unisexual male catkins were removed, and 25.0 and 3.7 per cent where no emasculation was done. The controls which were not emasculated and not hand pollinated, show that the trees are practically completely self sterile; only an occasional nut is set from self-fertilization.
Vegetative Propagation
In vegetative propagation the tree breeder has a very important tool. For instance, if a number of desirable phenotypes have been selected in the forest, they can be propagated vegetatively and planted under uniform conditions where it will be possible to "estimate" their genotype, without the time-consuming progeny testing. Trees propagated vegetatively from old mature trees usually will start flowering very soon after they become established; thus the necessity of doing pollination work in very large trees can be eliminated. Furthermore, it enables the tree breeders to maintain trees of a desirable genotype unaltered for an indefinite length of time without first establishing pure lines through inbreeding. Finally, it may be possible to make valuable individuals available to the forest owners for field planting if they can be propagated vegetatively in large enough numbers at low cost.
Compared to propagation by grafting, the rooting of cuttings is both simpler and cheaper, if it can be done. Chestnut cuttings are, unfortunately, very difficult to root. In the past six years numerous experiments have been conducted in order to find a way to root the various chestnut species. We have tried to root dormant, as well as greenwood, cuttings, the conventional twig cuttings as well as leaf-bud cuttings; numerous hormone treatments using several different hormones in solution and as powders, over a wide range of concentrations, have been tried; a special chamber in which an automatic atomizer nozzle sprays the cuttings intermittently has been used. Results have always been poor. Dormant cuttings have broken dormancy, sent out new leaves, formed an abundance of callus on the basal end, but failed to develop any roots, and finally after several months have died. Greenwood cuttings also have failed to develop roots in almost all cases. The best results have been obtained with leaf-bud cuttings. In some cases 10 to 20 per cent have rooted; here, however, the difficulty has been the failure of the bud to break dormancy and start growth, and all the rooted cuttings have eventually died.
The rooting by airlayering has been tried in a few cases. Airlayering is the rooting of twigs while they are still attached to the tree. Some distance from the terminal end of the twig an oblique cut is made, or the bark is removed around the twig for about 3/4". The cut or ringed area is treated with a hormone powder, wrapped in sphagnum moss and covered with a wrapping of polyethelene. Attempts to root twigs on older trees by this method have so far failed. Recently successful rooting of twigs on young seedlings by airlayering has been reported from Spain, and from France comes the report that stooling of young seedlings is highly successful. In the stooling method the young plants are cut off a short distance above the ground level. As new shoots grow out, their basal ends are gradually covered with soil until a 5-6" mound has been formed. Left in this manner they may develop their own root system and can eventually be detached from the mother root. That the rooting of young seedling material should be possible, while that from older trees will not root, is not unusual. It is generally accepted that the younger the tree from which the cuttings are taken, the easier the cuttings are to root. Experiments along these lines are planned for 1954.
Cooperative Hybrid Chestnut Plantations
In last year's report we described our hybrid test plots established in cooperation with the U.S.D.A., Bureau of Plant Industry, Division of Forest Pathology.
On March 18, 1953 a new plantation was started at Grafton, West
Virginia. As usual, we furnished 50 plants for this test plot.
From the reports from Dr. J. D. Diller, of the then Division of Forest Pathology, our hybrids so far have shown a promising performance, although their average growth rate so far is slightly slower than that of the U.S.D.A. hybrids and straight Chinese chestnut. From the standpoint of blight resistance and growth habit they are at least equal to the two other sources and may be slightly better; however, it is still too early to make any definite evaluation of the results.