The interaction of Thielaviopsis basicola (Berk. and Br.) Ferr. and Rhizoctonia solani Kuhn as pathogens of seedling cotton.

Persistent Link:
http://hdl.handle.net/10150/185302
Title:
The interaction of Thielaviopsis basicola (Berk. and Br.) Ferr. and Rhizoctonia solani Kuhn as pathogens of seedling cotton.
Author:
Chapman, Margaret Ann
Issue Date:
1990
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Soil inoculum density and the incidence of black root rot of cotton caused by Thielaviopsis basicola were monitored in two adjacent fields planted mid-April to Gossypium hirsutum 'Acala 1517' at Duncan, AZ (1160 m elev.). Forty soil cores (3.5 x 15 cm) were taken from the root zone and 80 plants were collected biweekly in the two fields from 5/7/87 to 9/28/87. The inoculum density (cfu/g air-dried soil) was determined by plating soil dilutions onto a selective medium. Disease severity was rated on a scale of 1 (slight cortical decay) to 4 (severe cortical decay). Mean inoculum density in Field 1 soil was 65 cfu/g soil and 20% of the seedlings were infected with a severity rating averaging 1.6. In Field 2 the inoculum density, percentage of infected plants, and disease rating were 225 cfu/g soil, 93, and 3.2, respectively. No cortical decay was noted after June 6 in either field. Yields were similar in both fields. Field and laboratory studies indicate that high disease incidence of black root rot caused by T. basicola results in reduced incidence of seedling disease caused by Rhizoctonia solani. For example, 1 mo after untreated seeds of G. barbadense 'Pima S-6' were planted into a cotton field in Coolidge, AZ with natural inoculum levels of 12 cfu/100 g soil and 225 cfu/g soil of R. solani and T. basicola, respectively, 98% of the plants were infected by T. basicola while only 2% were infected by R. solani. Eleven out of the 12 R. solani propagules were pathogenic to cotton. The same levels of inoculum, were added to autoclaved field soil in growth chambers at 18 C and 5200 lux light in four treatments. The first treatment, T. basicola alone, caused a 98% incidence of black root rot. Rhizoctonia solani alone resulted in a 38% incidence of disease, whereas inoculum of T. basicola and R. solani, together caused a 98% and 17% incidence of disease caused by T. basicola and R. solani, respectively. Simultaneous inoculations of 4-day-old G. hirsutum 'DP 90' seedlings on water agar plates with inoculum of T. basicola and R. solani resulted 5 days later in a significant decrease in infection by R. solani as compared to that in the seedlings inoculated with R. solani only.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Agriculture
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Plant Pathology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Hine, Richard

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleThe interaction of Thielaviopsis basicola (Berk. and Br.) Ferr. and Rhizoctonia solani Kuhn as pathogens of seedling cotton.en_US
dc.creatorChapman, Margaret Annen_US
dc.contributor.authorChapman, Margaret Annen_US
dc.date.issued1990en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSoil inoculum density and the incidence of black root rot of cotton caused by Thielaviopsis basicola were monitored in two adjacent fields planted mid-April to Gossypium hirsutum 'Acala 1517' at Duncan, AZ (1160 m elev.). Forty soil cores (3.5 x 15 cm) were taken from the root zone and 80 plants were collected biweekly in the two fields from 5/7/87 to 9/28/87. The inoculum density (cfu/g air-dried soil) was determined by plating soil dilutions onto a selective medium. Disease severity was rated on a scale of 1 (slight cortical decay) to 4 (severe cortical decay). Mean inoculum density in Field 1 soil was 65 cfu/g soil and 20% of the seedlings were infected with a severity rating averaging 1.6. In Field 2 the inoculum density, percentage of infected plants, and disease rating were 225 cfu/g soil, 93, and 3.2, respectively. No cortical decay was noted after June 6 in either field. Yields were similar in both fields. Field and laboratory studies indicate that high disease incidence of black root rot caused by T. basicola results in reduced incidence of seedling disease caused by Rhizoctonia solani. For example, 1 mo after untreated seeds of G. barbadense 'Pima S-6' were planted into a cotton field in Coolidge, AZ with natural inoculum levels of 12 cfu/100 g soil and 225 cfu/g soil of R. solani and T. basicola, respectively, 98% of the plants were infected by T. basicola while only 2% were infected by R. solani. Eleven out of the 12 R. solani propagules were pathogenic to cotton. The same levels of inoculum, were added to autoclaved field soil in growth chambers at 18 C and 5200 lux light in four treatments. The first treatment, T. basicola alone, caused a 98% incidence of black root rot. Rhizoctonia solani alone resulted in a 38% incidence of disease, whereas inoculum of T. basicola and R. solani, together caused a 98% and 17% incidence of disease caused by T. basicola and R. solani, respectively. Simultaneous inoculations of 4-day-old G. hirsutum 'DP 90' seedlings on water agar plates with inoculum of T. basicola and R. solani resulted 5 days later in a significant decrease in infection by R. solani as compared to that in the seedlings inoculated with R. solani only.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectAgricultureen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlant Pathologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHine, Richarden_US
dc.contributor.committeememberStranghellini, Michaelen_US
dc.contributor.committeememberNelson, Merritten_US
dc.contributor.committeememberAlcorn, Stanley M.en_US
dc.contributor.committeememberPepper, Ianen_US
dc.identifier.proquest9114051en_US
dc.identifier.oclc710835715en_US
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