Pathogenicity of sclerotia-forming isolates of Colletotrichum truncatum to soybeans (Glycine max) and the effect of soil temperature on root infection
Khan, Mahmood
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https://hdl.handle.net/2142/20977
Description
Title
Pathogenicity of sclerotia-forming isolates of Colletotrichum truncatum to soybeans (Glycine max) and the effect of soil temperature on root infection
Author(s)
Khan, Mahmood
Issue Date
1991
Doctoral Committee Chair(s)
Sinclair, James B.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Biology, Botany
Agriculture, Plant Pathology
Language
eng
Abstract
Pathogenicity of three sclerotia-forming isolates and a nonsclerotia-forming isolate of Colletotrichum truncatum, causal agent of soybean anthracnose, to soybean roots was studied in an aeroponics system, and their pathogenicity to above-ground parts and effect on yield were examined in the field. The effect of soil temperature on root infection by the sclerotia-forming isolates was studied in soil temperature tanks at the University of Illinois at Urbana-Champaign (UIUC).
Sclerotia-forming isolates Ct-1, Ct-3, Ct-4, and a nonsclerotia-forming isolate, Ct-2, were pathogenic to soybean roots, causing root and shoot length reduction in cv. Corsoy 79. Three root inoculation methods, viz. conidial suspension with or without methylcellulose and sponge inoculation, were effective in establishing infection on soybean roots.
Soybean cultivars A. K. (Kansas), Boone, Corsoy 79, and Williams 82, with differential resistance to foliar infection, were all susceptible to root infection. However, they exhibited different levels of susceptibility to root infection by Colletotrichum truncatum isolates; the greatest susceptibility was shown by Williams 82, followed, in descending order, by Corsoy 79, A. K. (Kansas), and Boone.
Lesion development on roots of these cvs. and significant differences in lesion length were found between cvs. and among isolates when inoculated and placed under misting at 1 sec every 30 min in an aeroponics chamber.
Foliar inoculation of the four cultivars with three isolates of Colletotrichum truncatum, Ct-1, Ct-2, and Ct-3 in the field, caused infection and significantly reduced yields in three cultivars. The estimated loss due to anthracnose for A. K. (Kansas) was 17%, for Corsoy 79 23%, and for Williams 82 30%.
Root infection by Colletotrichum truncatum, isolates Ct-1 and Ct-3, increased with an increase in soil temperature in soil temperature tanks. The highest root infection was recorded at 30 C, and the lowest at 20 C. The greatest mean percent root and hypocotyl infection was recorded at 30 C for Williams 82 followed, in descending order, by A. K. (Kansas), and Boone. The interaction between cultivar resistance and temperature showed the greatest root and hypocotyl infection at 30 C for the three soybean cultivars.
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