Professor Aldo Pavari, Director of the Stazione Sperimentale di Selvicoltura at Florence, visited this country in the summer and fall of 1946, under the sponsorship of the UNRRA, and spent four days with me at our plantations, learning our methods and getting acquainted with the blight resistant hybrids we have been developing by the breeding together of oriental and native chestnuts. Prof. Pavari visited also the plantation of the Division of Forest Pathology at Beltsville and elsewhere, and other plantations in the west. In December we shipped to Florence, Italy, nuts of our best hybrids, and in March, scions for grafting—also this summer (1947) pollen of some of our best trees. On October 15 of this year (1947) we sent another shipment of nuts. Thus we may be able to give Italy the advantage of the progress we have made to date.
Regarding the susceptibility to the blight of the European or Spanish Chestnut (C. sativa) we have had the following experience. Our winter temperatures appear to be too severe for this species. Dying back is sure to occur, at least at our Hamden, Connecticut plantations, marked more or less according to the degree of cold; and on the dead parts Endothia then appears, to later invade the parts still living. In 1932 I received nuts of C. sativa from France from Professor Hochreutiner of the Geneva Botanic Garden, from Professor Uldrich of the Berlin Botanic Garden, and also from France from Dr. Guillaumin of the Jardin de Plantes at Paris. Although I have given the resulting plants much attention they continually die back each year so that we have only two or three individuals that are more than six feet high. But Professor Pavari says in recent correspondence (July 15, 1947) "Referring to Spanish chestnuts, after we have been assured that the fungus we have found and observed on Castanea crenata in Spain is really Endothia parasitica, we must admit that our hypothesis may be exact that Castanea vesca [sativa] presents in Spain races or types resistant to the disease." He goes on to say that the fact that the chestnut blight is so widespread at Naples and Avellino is at variance with my theory that cold winters are the predisposing cause, for in the regions mentioned the winters are mild and "very warm in comparison with those of Connecticut." The essential fact seems to be that the European or Spanish chestnut is very susceptible to the blight, perhaps as much so as is our native species, but that evidently certain individuals or races exist that are more or less resistant.
During the early part of 1947 we had a visit from Professor Cristos Moulopoulos of the University of Salonika, Greece. Although the disease had not then appeared in Greece, the pathologists there would like to be ready for it when it does come.
Pollinations in 1946 and 1947. Without going into details, the general purpose of the pollinations during these last two years has been to incorporate more and more of the resistant Chinese stock into our hybrids. Beginning in 1937, we crossed our best Japanese-American hybrids with Chinese, and we now have a considerable number of young saplings of flowering age, which have the pedigree: Chinese x Japanese-American. Unfortunately, in this cross the Chinese is usually dominant as regards habit, but not always. We have some tall, straight-growing individuals of this combination which may well be the forerunners of a blight-resistant forest stock for America.
Therefore, during 1946 and 1947 we have been crossing these fine Chinese x (Japanese-Americans) with the following:
1. Our best Chinese
2. American-Chinese and Chinese-American
3. American (C. dentata)
4. Our best Japanese-Americans
5. Among themselves
For it is the ultimate aim of this work to develop a race of tall, hardy, blight resistant individuals which will breed true and thus of themselves re-establish the chestnut tree in the forests of Eastern North America. As everyone knows, the re-establishment of the chestnut as a forest tree can not be done in a few years or even a score of years, but by continued breeding and patience and perseverance it can be done. The materials are at hand, i.e. tall, erect growth, and blight resistance; and with persistent effort the desired combination can be made.
For (1) above we were fortunate in 1946 in receiving a supply of pollen from tall-growing Chinese trees, through the kindness of Mr. Michael Evans of Greenville, Delaware and Professor Maurice A. Blake of the New Jersey Agricultural Experiment Station.
As a result of our pollinations in 1946, in which 72 combinations were made, we harvested and planted in our cold frames in October 479 hybrid nuts, a large proportion of which germinated, so that this summer (1947) we have set out in our nurseries about 325 hybrid seedlings.
In 1947 we have made 58 combinations in which 213 branches were bagged; October 10-13 we gathered 380 hybrid nuts resulting from these cross pollinations. The large yield of 1947 is doubtless the result in part of a good growing season, for there was plenty of rain—at times almost too much—in southern Connecticut. One drawback was the cold period during the latter part of June. From the fifteenth to the twenty-sixth the minimum temperatures were 55 or below—on three days as low as 50. This set back the flowering period four days to a week later than usual, depending upon the species or hybrid.