Document Type

Thesis - Open Access

Award Date

1984

Degree Name

Master of Science (MS)

Department

Plant Science

First Advisor

Martin L. Carson

Abstract

Resistance enables crop plants to defend themselves against their pathogens or against a level of disease deleterious to the crop Frequently, the relative success of other control measures is determined by the precision of their use. Resistance, however, is not so subject to external variation. Concerns for the quality of the environment when chemicals are used to control disease illustrates the importance of genetic control of plant diseases. Whereas the protection of crops of high unit value (fruit orchards, vegetables, ornamentals) by the use of fungicides is considered profitable, hereditary control remains the most economically feasible strategy to protect crops of low unit value such as corn, wheat, rice and forages. Fortunately for breeder-pathologists, most species of cultivated plants possess adequate resistance to most of their parasites. The so-called "green-revolution" hinges largely on the development and maintenance of adequate resistance to an array of plant pathogens in potentially high yielding cereal crops as a means of continued crop production. Corn is the most important plant native to the American continent, with the United States producing about 44% of the world crop. World reduction in corn production from diseases is estimated to average 9.4%. Losses in the Corn Belt of the USA were in the range of 7 to 17% in 1980. As disease resistant corn hybrids are developed, new diseases evolve in what may be described as the co-evolutionary race between corn pathogens and host resistance systems. An example of this is the occurrence of a new bacterial disease of corn called "Goss' bacterial Wilt and Blight", or "Leaf Freckles and Wilt" (LFW) which first appeared in Nebraska in 1969. Because of its rapid geographical spread in the Corn Belt of the USA, including South Dakota, and its demonstrated ability to severely reduce yields, attention is being directed at developing maize genotypes that are resistant to the pathogen. A fundamental requirement in breeding for resistance to an unfamiliar disease is· to first obtain knowledge of the genetics of the particular pathosystem. The objectives of the research reported herein were: a) to determine the mode of inheritance to LFW; b) to estimate the number of genes involved in disease reaction; c) and also to estimate heritability of resistance in the broad sense; and, d) to cytologically locate the factors on corn chromosomes that condition resistance to LFW.

Library of Congress Subject Headings

Corn -- Disease and pest resistance

Format

application/pdf

Number of Pages

72

Publisher

South Dakota State University

Rights

No Copyright - United State
http://rightsstatements.org/vocab/NoC-US/1.0/

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