Pecans 



Although severe freezes in the winter or late spring have occasionally caused damage to 

 pecan trees and crops, first fall frosts are the most frequent cause of cold damage. This is 

 especially true of the northern part of the southern pecan belt where commercial varieties do 

 not ripen early enough to avoid frost injury. 



Consequently pecan improvement projects of ARS emphasize early maturity along with 

 winter hardiness, disease resistance, fruitfulness, and other desired characteristics. At the U.S. 

 Pecan Field Station in Brownwood, Tex., more than 8,000 hybrids have been fruited during 

 some 30 years of breeding and 5 superior pecan hybrids named and introduced. Other prom- 

 ising selections are being evaluated and two of them will probably be introduced in the near 

 future if their performance is up to expectations. At the U.S. Horticultural Field Station, 

 Meridian, Miss., several new varieties originated by State experiment stations and private 

 individuals are being evaluated for desired characteristics including hardiness. 



In developing hardy pecans, a problem is the long, hot growing season required to 

 mature the nuts, coupled with their late-blooming characteristic. Most common varieties of 

 pecans require more warm weather to induce bloom (about 200 hours of frost-free weather) 

 than do most other deciduous fruits. 



A member of the hickory family, the pecan tends to be less cold hardy and disease resis- 

 tant than other kinds of hickory. With the aim of combining the good quality of the pecan 

 with the early maturity and disease resistance of other hickories, ARS scientists are working to 

 develop improved varieties of the hiccin — a hybrid made by crossing pecan with other hick- 

 ories. Forty-six second generation hybrids are now being back crossed to obtain the desired 

 characteristics of both the pecan and other hickory nuts. Breeding and evaluation research 

 on hicans is being done at Beltsville, Md. 



Walnuts 



Commercial production of Persian (English) walnuts in this country is mostly confined 

 to California and Oregon due to lack of cold hardiness. Some Persian walnut trees grow and 

 bear fruit in northern and eastern sections of the country but usually only where they are 

 sheltered. 



Black walnuts or some varieties of them are hardy in most parts of the United States. 

 Though the nuts are harvested from wild trees and sold in considerable volume, commercial 

 plantings are limited. The major emphasis in walnut research has been to develop improved 

 Persian walnuts or hybrids combining the desirable characteristics of Persian varieties with 

 the hardiness and disease resistance of other kinds of walnuts. 



Manregian (Plant Introduction 18256), a hardy walnut collected many years ago in West 

 China by a USDA plant explorer, is an example of a foreign plant introduction which has con- 

 tributed to the development of hardier commercial walnuts. Seedlings of this variety are now 

 widely used as hardy rootstock by walnut growers in Oregon. Also the hardy new fruiting 

 variety Adams originated as an open-pollinated seedling of P.I. 1826. 



Another source of hardiness used in selecting and breeding new walnut varieties is ma- 

 terial brought home by USDA plant explorers from the Carpathian mountains of Poland. 

 A few of the varieties of Carpathian origin have a bitter after-flavor but several have kernels 

 of acceptable quality and show promise over a wide area because of their hardiness. In test 

 plantings at the Plant Industry Station, Beltsville, Md., the Carpathian varieties Colby, Burtner, 

 and McDermid are very productive. Burtner vegetates and blossoms 3 weeks later than other 

 varieties which may enable trees of this variety to escape late spring frosts in many areas. 



Crosses are also being made with Eastern black walnuts and Persian varieties but partial 

 sterility of F-1 hybrids has complicated such hybridization. More hybrids will be made, how- 

 ever, and the most promising ones backcrossed to better varieties of Persian and Eastern 

 black walnuts. 



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