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|Title:||Sources and Inheritance of Resistance to Anthracnose Stalk Rot of Corn|
|Author(s):||Carson, Martin Leroy|
|Department / Program:||Plant Pathology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Plant Pathology|
|Abstract:||Stalk rots are some of the more important diseases of dent corn (Zea mays) in the Midwest. In recent years anthracnose leaf blight and stalk rot, caused by Colletotrichum graminicola, have increased in prevalane in the warmer, humid corn-growing regions of the U.S. Recent evidence shows a great potential for anthracnose stalk rot to cause yield losses. Host genetic resistance has been successfully used to reduce loss due to Diplodia and Gibberella stalk rots of corn, but this resistance does not appear to be effective in controlling anthracnose stalk rot. Knowledge about available sources of resistance and how this resistance is inherited would aid plant breeders in breeding for resistance to anthracnose stalk rot. The objectives of these studies were to evaluate a wide array of corn germplasm for anthracnose stalk rot reaction, locate superior sources of resistance, determine how resistance is inherited in several adapted corn inbred lines, and identify the chromosome arms carrying genes for resistance in the inbred A556.
Six hundred and twenty-two corn inbred lines, breeding stocks, and genetic stocks were evaluated for anthracnose stalk rot reaction with artificial inoculation in 1977. Forty entries, classified as resistant in 1977, were evaluated further in 1978 both as lines or stocks and in testcrosses with the intermediately susceptible inbred line A632. Inbred MP305 was the only entry that appeared highly resistant as a line per se and in hybrid combination with A632. A genetic study of the inbreds MP305 and A632, the F(,1), F(,2) and F(,1) X MP305 generations in 1979 indicated that MP305 has two dominant genes, one with a major and one with a minor effect for resistance to anthracnose stalk rot.
The inheritance of resistance to anthracnose stalk rot in five corn populations derived from the single crosses, A556 X C123, A556 X B73, A638 X C123, Oh43 X C123, and R177 X C123 was studied in 1977, 1978, and 1979 following artificial inoculation. In 1977 and 1978, the populations consisted of the inbred parents, the F(,1), F(,2), B(,1) and B(,2) generations. In 1979 the study was expanded to include the F(,3), B(,11), B(,22), B(,1S), and B(,2S) generations. Additive genetic effects accounted for over 90% of the variation in generation means in the combined analysis in all populations. Estimates of genetic variances were highly variable, but in general, narrow-sense heritabilities were in the medium to high range.
Nineteen reciprocal chromosomal translocation testcross populations of the form: (translocation stock X A556) X C123 were evaluated for anthracnose stalk rot in the field in 1979 following artificial inoculation. Partial seed set in translocation heterozygotes significantly reduced the severity of stalk rot. Linkage studies showed the long arms of chromosomes one, four, six and eight; and the short arm of chromosome six to carry genes or blocks of genes for resistance to anthracnose stalk rot. The relatively small number of genes involved indicates that some type of backcross breeding scheme would be an effective method of developing inbred lines resistant to anthracnose stalk rot.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
|Date Available in IDEALS:||2014-12-14|