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  • Author or Editor: Edward Ryder x
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In the last 2 decades, 2 cultivars of lettuce (Lactuca sativa L.) have dominated the western U.S. lettuce industry. The first, ‘Calmar’ was released by the University of California in 1960. For several years in the mid-1960's, it was planted on nearly all the spring, summer and early fall acreage in the Salinas Valley and other coastal districts in California. It is a large, vigorous cultivar of the Great Lakes type. The second, ‘Vanguard’, was released by the USDA in 1958 and for many years has been the mainstay cultivar for early spring production in the Imperial Valley and other desert districts. Each cultivar has spawned a group of selections, a ‘Calmar’ group and a ‘Vanguard’ group, which have increased the adaptive range of the original cultivars.

Open Access
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Abstract

Lettuce mosaic virus (LMV), has been one of the most destructive diseases of lettuce (Lactuca sativa L.) in nearly all production areas of the world. One of the major goals of the USDA Lettuce Breeding Project in Salinas, California, has been to develop mosaic resistant cultivars. We began this program in 1959 with a search for sources of resistance. Three years later, we identified 3 resistant Plant Introductions from Egypt (3).

Open Access
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The similar titles of Namkoong’s paper and this one invite comparison, not so much for their similarity as for the differences in sampling rationale. The main difference is in the nature of the populations that are being sampled. The population in the field is usually far away. Further, it is of unknown size and its genetic makeup and complexity can only be guessed.

Open Access
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Lettuce mosaic has been a serious virus disease for lettuce in all locations worldwide where lettuce has been grown. Consequently, the disease and its virus have been well studied. Lettuce plants react to lettuce mosaic virus in a variety of ways. The most common susceptible reaction is an overall vein clearing and mottling, followed by leaf recurving, leaf distortion, and stunting. However, some susceptible types manifest a mild mottling with little additional distortion. Others develop a necrotic reaction, which may be severe, mild, or seasonal. Finally, there are at least three resistant reactions, most frequently appearing as a systemic infection manifested with restricted yellowish lesions. Research is ongoing to sort out the various reactions and their genetic bases. This report describes the inheritance of the severe necrotic reaction and its relationship to the resistant reaction conferred by the allele mo-1. Several previous crosses among necrotic types indicate that the same necrotic allele is operating except that found in `Bibb'. Several crosses were studied. The cross `Salinas' (mot.) × `Crisp As Ice' (nec.) showed that necrotic is due to a single dominant allele. The cross `Salinas 88' (res.) × `Maikonig' (nec.) produced three phenotypes in F2, indicating the action of two loci. The crosses PI 251245 (res.) × `Prizehead' (nec.) and `Vanguard 75' (res.) × `Prizehead' disclosed two recombinant phenotypes, mottled and resistant-necrotic. Necrotic is dominant to nonnecrotic in both susceptible and resistant phenotypes. The genes are inherited independently.

Free access
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Abstract

A major goal in our lettuce (Lactuca sativa L.) disease resistance breeding program has been the development of cultivars resistant to big vein. Big vein is expressed primarily as vein clearing and stiffening of outer leaves giving a bushy effect. It is caused by big vein agent, a virus-like entity, which is transmitted into the roots of the plant by a root-feeding fungus Olpidium brassicae (Wor.) Dang. Symptoms are most commonly expressed during periods of low air temperature and in heavy wet soils (4, 5). Consequently, in the United States it is a common problem in the West during the early spring growing period. ‘Sea Green’ is a new cultivar with big vein resistance.

Open Access
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Abstract

Big vein has been a problem for growers of lettuce (Lactuca sativa L.), particularly in the western United States, for many years. The principal symptom, vein clearing, lends an unsightliness to the lettuce that may reduce its market value (7). During periods of low temperatures, big vein may delay or prevent head formation and thus reduce the harvest recovery (4).

Open Access
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Abstract

The artichoke is a popular vegetable in Italy, Spain, and France. The American consumer, upon first encountering this bristly vegetable, may wonder why. Dealing with the artichoke, either as a cook or around the dinner table, may seem more like a confrontation than a culinary venture, and the average artichoke novice may be happy with a stand-off.

Open Access
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Abstract

Although plant breeding is very old, it has, at least during recorded history, seldom been short of new ideas and concepts that have made breeding procedures more and more powerful and effective. It is reasonable to speculate that the first act of plant breeding was the use of seeds from superior plants for the next year’s crop. Development of new technologies in the intervening years, has added to the power and versatility of the plant breeder’s art. Some of these changes have been spectacular, others rather modest.

Open Access
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Abstract

Major reliance for protection of lettuce plantings from lettuce mosaic virus (LMV) in the United States is placed on a seed indexing procedure developed in California (1). The only major crisphead lettuce (Lactuca sativa L.) cultivar in the United States with resistance to lettuce mosaic has been ‘Vanguard 75’, released by the U.S. Dept. of Agriculture, cooperatively with the California Agricultural Experiment Station, in 1975 (3). ‘Vanguard 75’ is one of the important cultivars in the mid-February to early March harvest period in the desert districts of California and Arizona. It is also a major early cultivar in the spring season of the San Joaquin Valley. ‘Winterset’ is a new lettuce mosaic-resistant crisphead lettuce. It is suitable for the same periods and districts as ‘Vanguard 75’ and, in addition, is adapted for production in late winter in the desert.

Open Access