In southern Connecticut the 1950 season for vegetative growth and development was excellent except for the dry period in September. The chief fault lay in much more cloudy weather than usual,[31] and the deficiency in sunlight coupled with a slightly lower average temperature in the spring, and cool nights, combined to delay the chestnut flowering season for as much as ten days. The main body of our cross pollination experiments did not begin until July 4, whereas last year it began on June 23 and 24, and was nearly completed by July 4.
[31] For example, the report of the U. S. Weather Bureau at New Haven, Conn., for May, 1950, says, "The feature of the month was the lack of sunshine which retarded the growth of crops in this area." See also report of the New York City Station for April, 1950.
This year 103 crosses were made, not all different combinations, but each one with either different or reciprocal parents. The principal combination was a cross of Japanese chestnut with Chinese-American or American-Chinese, a mixture that in recent years has given excellent results. This year also, as in the past, our CJA's were crossed with American chestnut.
[Illustration: Fig. 1. Cross pollinating Chinese chestnuts. Sleeping Giant Plantation, Hamden, Conn. Trees near left of center and at left, with drooping catkins, are Japanese-American hybrids. Photo July 13, 1950, by B. W. McFarland.]
~Cooperation with Italy.~ A considerable part of the cross pollination work this year has been undertaken for the benefit of the Italian authorities, namely experiment stations at Florence and Rome. This has been done at the suggestion of the Division of Forest Pathology, Beltsville, Md., which has been working along the same line.
As is now generally known, the chestnut blight was discovered in Italy in 1938, and has been making rapid headway in a country 15 percent of whose forests are in chestnut. To the Italians the chestnut means much as an article of food. They use the timber also, and the various ages of coppice growth in many ways[32]. Particular effort this year has been directed toward the breeding of promising nut-bearing types for them and especially resistant strains that bear large nuts like the cultivated European chestnut.
[32] Graves, Arthur Harmount. Breeding Chestnut Trees: Report for 1946 and 1947. 38th Ann. Rept. Northern Nut Growers Assn. p. 85. 1947.
Now, we have found that many of our Chinese chestnuts are practically immune to the blight. Even if the disease does appear, in most cases it is in the outer bark only, and is soon healed over. Moreover, the Chinese chestnut has a large nut, comparable in size to the cultivated Europeans with pollen from our best Chinese trees, and at the same successful crosses of the European and Chinese are made.
Last fall, as a result of an article in the New Haven Register by Mr. A. V. Sizer, I learned of two European chestnut trees of bearing age in New Haven back yards. So, this summer we have crossed these Europeans with pollen from our best Chinese trees, and at the same time have taken the pollen from one of them (in the other the pollen was sterile) and applied it to the female flowers of our Chinese trees. Most of the resulting nuts have been sent to the Italian scientists in the hope that some of them will develop into desirable nut-producing, disease-resistant hybrids. Some will be retained for testing here. If the resulting trees are not sufficiently blight-resistant, they will be crossed again with the Chinese.
In the summer we received by air mail from Dr. Aldo Pavari, of the Stazione Sperimentale di Selvicoltura in Florence, Italy, two tubes of pollen of the European chestnut, Castanea sativa, of the varieties pistolese and selvatico. These pollens were also applied to our best Chinese trees. They resulted in 12 good nuts which have been shipped to Dr. Pavari.