SONG News Spring 1992 no. 40

The Chestnut Constellation Also Rises

There have been many growers who have promoted the cause of chestnuts over the years. Chestnuts roasting on the open fire ... the vision which has kept growers struggling through establishment problems, manganese deficiencies, pH problems, chestnut blight, drainage deficiencies etc. This year, there are two world-class chestnut meetings which are to bring sweetness and light to the growing of the sweet chestnut. Herewith are a few abstracts of the action. Interested Ontario growers are invited to follow up on the leads which are mentioned with each focus of activity. Follow-up and report back to future SONG meetings on what you have found!

The selected abstracts given herein are taken from: The International Chestnut Conference, Morgantown, West Virginia, July 10-14,1992

Chestnut Forests and Chestnut Cultivation in Switzerland. Ursula Heiniger and Marco Conedera, Swiss Federal Institute for Forest, Snow and Landscape Research. CH-8903 Birmensdorf and Station South of the Alps, CH-650I Bellinzona, Switzerland.

Due to human activity, the European chestnut (Castanea sativa) became the dominant tree species in the colline and submontane (granite) regions south of the Alps. It is cultivated in orchards, sprou|-forests and coppices with standards. In the rural areas, it was important as a producer of chestnuts for nutrition and forage, of litter, of timber, of stakes for vines, of firewood, of tannin, and also as an erosion-protector. The introduction of the potato in 1810, the drastic change of the economy in the middle of the present century, and the occurrence and rapid spread of chestnut blight (caused by Cryphonectria parasitica), led to the neglect of the chestnut stands. Without silvicultural measures, the chestnut seemed doomed to gradually disappear.

In the 1950's, two programs were initiated: a) the selection and breeding (C. sativa x C. crenata) of blight-resistant chestnut, and b) the evaluation of the substitute tree species. The spontaneous arrival of hypovirulence, together with a new awareness of the tree's beauty and it's value for the landscape awakened a new interest in chestnut cultivation. The Forest Service and the "Chestnut Working Party" have recently taken the initiative to restore the chestnut stands by supporting tending operations, conversion of coppices to timber forest, and planting of orchards with selected trees from Switzerland, Italy and France. Poor nut quality and ring shake need further research.

Small stands of chestnuts are also found north of the alps. Recently, several foci of chestnut blight were found there, and santitary fellings were undertaken and hypovirulent C. parasitica strains will be introduced.

Ecology of Chestnut Blight and american Chestnut Survival in Appalachian Understory Forest Sites in Relation to Biocontrol of Blight. G. J. Griffin, Department of Plant Pathology, Physiology and Weed ScieTTces, VirginiaTech, BlacksburgVA 24061 USA.

American chestnut generally exists as a small tree in the understory of forests in the Appalachians, except on some xeric sites where canopy or subcanopy chestnuts may be found. Blight incidence of chestnut sprout clusters ranged from 0 to 48% on mesic sites with a high level of hardwood competition and a more open canopy, and from 34 to 80% on xeric sites with low hardwood competition and a more open canopy. Chestnut sprout cluster survival ranged from 90 to 100% on mesic sites and from 82 to 100% on xeric sites. Irradiance levels along transects in xeric understories were greater than in mesic understories. Chestnut in mesic understories received high levels of irradiance through small canopy gaps for only short time periods. Non-lethal, superficial blight cankers were found mainly on canopy or subcanopy chestnuts on xeric sites. Shallow cove mesic sites had the highest combined densities of large diameter chestnut stumps and live chestnut sprouts, compared to mesic deep cove and slopesites or xeric sites, and may be the best sites for blight management with hypovirulence and/or grafting blight-resistant chestnut clones following clearcutting.

Ecology and Paleoecology of Castanea dentata in Eastern North American Forest. Frederick L. Paillet, U.S. Geological survey, Box 25046, Denver Federal Center, Denver, CO 80225 USA.

American chestnut (Castanea dentata) was once an important forest tree in New England, but is neglected in most modern ecological studies. Recent surveys of surviving chestnut populations indicate that chestnut sprput clones are an important part of the understory jn many eastern woodlands in spite of blight, shrub competition, an almost complete lack of sexual reproduction, and vegetative reproduction limited to sprouting from the root collar. Population studies suggest that chestnut sprouts have increased as a percentage of total biomass on some sites. Survival of the species in the presence of blight results from sprouting characteristics and not blight resistance.

Studies in southern New England indicate that most surviving chestnut sprouts originated as seedlings rather than from the stumps of former canopy trees. For example, the dense population of sprouts on Prospect Hill at Harvard Forest in north-central Massachusetts is interpreted as a "halo" of chestnut regeneration surrounding woodlands where chestnut formerly was a canopy-dominant. In contrast with these regenerating woodlands, the limited chestnut sprout population in the old growth forest Pisgah Tract in southern New Hampshire indicates that chestnut reproduction was negligible in some stands where chestnut was canopy-dominant.

These results are used to construct a model seedling chestnut reproductive cycle as a two-step process, namely seedling establishment followed many years later by the release of suppressed stems. Although a number of species exhibit similar strategies, the special adaptations of chestnut seedling sprouts for long-term "storage" in the understory may account for some of the differences between the abundance of chestnut pollen relative to that of other trees in Holocene sediments. The sprout-storage strategy in prehistoric forests is illustrated by pollen data from north-central Massachusetts. Regional pollen influx to Black Gum Swamp at Prospect Hill displays a rise about 2000 years ago from trace amounts to an average of nearly 5% of the total arboreal pollen, indicating an average regional forest composition of about 15% chestnut. This pollen increase is found throughout southern New England, and always coincides with a small increase in spruce pollen. However, pollen from local catchments in forest hollows at Prospect Hill indicates a series of local fluctuations in chestnut in response to disturbance, with temporal peaks where chestnut may have been more than 50% of the local forest canopy.

Studies of the physiology of chestnut root collar tissue and the growth cycle of sprouts are used to identify some of the specific adaptations that make chestnut an efficient and effective survivor in oak-dominated stands. These studies concentrate on: I) the anatomy of root collar tissue; 2) effects of stem geometry and apical dominance on sprout survival; and, 3) comparison of american chestnut sprouts with those of other Castanea spp. The general similarity between chestnut and chinquapin (Castanea pumila), a tolerant shrub or small understory tree, indicates that both species exhibit characteristics that favor survival in suppression. Chinquapin occasionally "escapes" by release to produce large seed crops, whereas chestnut is capable of "storing" reproduction in the form of suppressed seedling sprouts.

Chestnut Blight (Cryphonectria parasitica) in Southern Switzerland: Influence of Hypovirulence and Management Practice. Marco Conedera and Ursula Heiniger, Swiss Federal Institute for Forest, Snow and Landscape Research Station South of the Alps, CH-6501 Bellinzona and CH-8903 Birmensdorf, Switzerland.

In Switzerland the main chestnut (Castanea sativa) growing areas are located south of the Alps. There, chestnut is the dominant tree species of the colline region covering over 15,000 ha. The European chestnut south of the Alps has been exposed to chestnut blight (Cryphonectria parasitica) for over forty years now. The survival of C. sativa is primarily due to its reduced susceptibility toward C. parasitica compared with C. dentata and to the appearance of hypovirulent strains of the fungus.

During 1988 we undertook an investigation to verify the distribution and the severity of the disease in southernSwitzerland. The field observations confirmed the wide distribution of the disease and showed the predominance of superficial cankers (probably due to hypovirulence) in all the areas investigated. The disease situation in a particular forest stand seems to be more dependent on management practice and management intensity rather than on site conditions.

Due to the presence of only a few vegetative compatibility groups of the fungus together with the fact that the chestnut stands are mostly mature and treated with only few interventions, the disease situation has improved. There also is substantial evidence for the presence of the virulent inoculum of C. parasitica, which could still constitute an obstacle to intensifying chestnut cultivation. Presently, there does not seem to be any danger for the survival of the species south of the Alps. The chestnut fruit groves can be revived and improved, provided all the necessary health-maintaining interventions characterizing the modern chestnut cultivation are undertaken.

Wildlife Value of Castanea dentata Past and Present, the Historical Decline of the Chestnut, and Its Future Use in Restoration of Natural Areas. James H. Hill, Maryland- National Capital Park and Planning Commission, Natural Resources Division, Chevy Chase, MD 20815 USA.

Castanea dentata was once the dominant climax hardwood in forests throughout much of the eastern United States and was a major source of food and habitat for wildlife. The passenger pigeon, black bear, white-tailed deer, squirrels and other rodents, turkey, mammalian and avian predators, several species of chestnut moths now presumed extinct, and other wildlife suffered as a result of the decline of the chestnut. Three important historical, catastrophic events other than migration caused by glaciation have impacted the distribution and abundance of the chestnut and thus created negative impacts on wildlife species that were facultative or obligate users of the tree. Clearing of large expanses of forest for farming, then logging of commercially valuable timber including chestnut, and finally the chestnut blight caused enormous change for wildlife, including some species dependent on large tracts of non-fragmented forest and its enormous mast crops. Many formerly abundant species of wildlife suffered great losses or even extinction as a direct result of loss of habitat and hard mast, along with market hunting, even before the blight. Today, Castanea dentata is relatively unimportant to wildlife. With the recent introduction of blight resistant Castanea dentata x mollissima, restoration efforts have begun in earnest. However, wildlife may benefit most if resistance to the fungal blight occurs or if the blight is controlled via viral pathogens on stump sprouting native chestnuts.

Critical Factors in Establishing Chestnuts in the Pacific Northwest. Robert Rachman, Oregon State University Extension Service, Corvallis, OR 97330-2144 USA.

Chestnuts are a highly productive orchard crop that can be grown in the Northwest on the better soils. Small planting and individual trees were brought to western Oregon by pioneers and British sailors where they have grown well for over 100 years.

Improved varieties can produce from one-to two tons per acre yearly at maturity if planted and grown properly. They can be mechanically harvested, similar to hazelnuts and walnuts. Marketing fresh chestnuts can be extended for several months through cold storage. Dried or frozen products can be marketed year around. Although acreage is growing slowly, some growers are enthusiastic about potential with $2 to $3 per pound vs. 42 cents for hazelnuts.

Orchard soil should be deep, well drained sandy loam or loam mixture. Irrigation is recommended in Oregon due to tree establishment and nut sizing in late fall when weather is normally dry.

Multiple harvests in October would place high quality fresh products in the market before exports arrive from Korea antf Europe. Available varieties include Colossal, LayerokaTMyoka, Skookum, Silver Leaf and others. Italian and Euro-Japanese hybrids were recently released from the Extension Service to nurseries.

Although relatively free from insects and blight, Pseudomonas spp. and secondary fungi have presented problems. Propagation studies showed early summer wire ringing of juvenile shoots surrounded by moist sawdust was the most successful and commercially acceptable propagation method of trees.

Survival and Naturalization of Chinese Chestnut in Connecticut, USA. Sandra Anagnostakis, The Connecticut Agricultural Experiment Station, Box 1106, New Haven, CT 06504 USA.

In April 1926 trees of Castanea mollissima, Plant Introduction number 58602 were planted in Killingly, Connecticut, USA. These were examined in 1965 by Richard Jaynes, who reported that seedlings from these trees were naturalizing in a neighboring, abandoned field. In 1992,28/67 of the original trees are still alive, and there are about twice as many naturalized seedlings in the transects examined. These trees are competing well with the other early succession hardwoods and produce abundant nuts every year. The nuts will be collected this year by the State of Connecticut Plant Nursery to be germinated, and seedlings will be sold to residents for planting to provide food for wildlife.

Chestnut Trees and Chestnut Blight: Reactions of Species of Castanea to the Pathogen, Sandra Anagnostakis, The Connecticut Agricultural Experiment Station, Box1106, New Haven, CT 06504 USA.

The Experiment Station has an excellent collection of species and hybrids of Castanea, planted from 1929 to 1992. These have been used for evaluation of resistance by inoculation with standard virulent strains of Cryphonectria parasitica. Peroxidase isozyme patterns from many of the trees have been compared to search for differences that might explain the differences in the reactions of the trees to chestnut blight infection.

Inheritance of Morphological Characteristics in Crosses of Chinese and American Chestnut. F. V. Hebard, The American Chestnut Foundation, Wagner Research Farm, Meadowview, VA 24361 USA.

Progeny from crosses of Castanea dentata and C. mollissima were examined for the occurrence of the following characteristics: green or red stem colour, stipule size, stipule dehiscence, lenticel size, density of simple hairs on twigs (twig hairs) and abaxial leaf midribs and secondary veins (vein hairs); and, the occurrence of simple hairs on interveinal areas of abaxial leaf surfaces (interveinal hairs). All characteristics but lenticel size appear to be controlled by one or two genes. Lenticel size was too difficult to score with reasonable accuracy on seedlings less than 1-year old. Unusual patterns of inheritance were observed in intercrosses of first hybrids of C. mollissima and C. dentata (F2s), perhaps due to their being interspecific crosses. Nevertheless, several conclusions can be drawn. Green stem colour from C. mollissima is probably controlled by two epistatically interacting, partially recessive genes. Occurrence of interveinal hairs on leaves of C. mollissima is probably controlled by a single dominant gene. High density of twig hairs on C. mollissima may be controlled by two dominant genes, perhaps by one dominant gene. High density of vein hairs and large stipule size on C. mollissima are controlled by one or two dominant genes. Large stipules on C. mollissima take much longer to senesce and dehisce than small stipules on C. dentata. This appears to be strictly related to stipule size and controlled by the same gene(s). The three hair characteristics are all linked, but recombination occurs. Twig hairs are linked with stipule size; stipule size is closely linked with vein and interveinal hairs. The stem colour determinations were the most interesting from a pathological perspective. The lack of redness in C. mollissima is probably due to lack of anthocyanin, and is probably directly linked with the lack of condensed tannins in C. mollissima which may be associated with blight resistance. The Clapper tree is a partially blight resistant, 3/4 C. dentata, 1/4 C. mollissima first backcross. When it was backcrossed again to C. dentata, the progeny only had red stems, whereas the Graves tree, also 3/4 C. dentata, yielded some progeny with green stems. This, and the pattern of inheritance of stem colour in other crosses indicated that the Clapper tree does not have any genes for green stem colour. These results suggest that the lack of condensed tannins in C. mollissima is probably not responsible for its blight resistance.

Phenology of Blooming and Fruiting Habits in Euro-Japanese Hybrid Chestnut. Giancarlo Bounous, James Hill Craddock, Cristiana Peano and Paolo Salarin, Istituto di Coltivazioni Arboree, Universita di Torino, 10126 Torino and Istituto di Frutticoltura Industriale, Universita di Torino, 10126 Torino, Italy.

Developmental stages of the growth cycle from bud swelling in the spring, through burr and leaf-drop in the autumn are described for hybrids of Castanea crenata and C. sativa. All stages are presented in photographic sequence which details the appearance of dormant vegetative and mixed buds, bud break, leafing out, staminate catkin development, catkin type (astaminate, brachystaminate, mesostaminate, longistaminate), varietal comparisons with regard to catkin type, androgynous catkin development, pistil late flower development, full bloom, fruit set, ripening, fruit drop, yellowing of the foliage and leaf fall. Emphasis has been placed on the floral sequence in order that future works on chestnut may refer more precisely to the particular developmental moment within the phenological phase "bloom".

Recent Introduction of European Chestnut Varieties into the USA. James Hill Craddock and Silvio Pellegrino. Istituto di Frutticoltura Industriale, Universita di Torino, 10126 Torino and 12 Asprofrut, 10100 Cuneo, Italy.

Growth of a chestnut industry in North America has been slowed, in part, by the unavailability of superior varieties, such as the famous "marron" types, found growing in Europe. Introductions into the USA were made of the best clones currently available in Europe. Selections were drawn primarily from the variety collections of the "Asprofrut" Association of Piedmont Fruit Growers. Graft incompatibility may involve cambial peroxidase isozymes, anmd samples of each scion type were sent to Dr. Frank S. Santamourof the U.S. National Arboretum in Washington, D.C. for isozyme typing. Grafting onto isozyme typed seedling rootstocks was accomplished at the nursery of Mr. Michael Dolan of Onalaska, Washington. This introduction represents the largest single introduction of European varieties into the USA in recent history, includes some of the best cultivars known, and should contribute significantly to the growing chestnut industry in the USA.

Provided by SONG. Feel free to copy with a credit.