Morphological and molecular identification, pathogenicity characterization of colletotrichum species on soybean, and the resistance of soybean genotypes

Colletotrichum species are filamentous fungi. Many species are important pathogens causing economic losses on a wide range of crop plants. Diseases caused by Colletotrichum species often are referred to as anthracnose. The species associated with soybean [Glycine max (L.) Merr.] have not been sufficiently studied in terms of their genotype discrimination and phylogenetic relationships. Moreover, there is little information on evaluation of soybean germplasm accessions for anthracnose resistance. Colletotrichum species were isolated from soybean petioles and stems with anthracnose symptoms from soybean fields in several states in the United States. Multi-gene sequence phylogenetic analyses resulted in a distinct group of isolates that were separated from other known Colletotrichum species. A representative isolate from this group was examined for its morphology, cultural characteristics, and pathogenicity on soybean. The phylogenetic and morphological analyses showed that this group was a new species and was named Colletotrichum incanum. Real-time PCR assays based on dsDNA-binding dye were developed using a region of the cytochrome c oxidase subunit 1 (cox1) gene to discern four Colletotrichum species, C. chlorophyti, C. incanum, C. truncatum, and Glomerella glycines (Colletotrichum sp.). To increase detection efficiency, two sets of duplex real-time PCR assays were established. Set 1 duplex assay distinguished C. chlorophyti and G. glycines, and the Set 2 duplex assay distinguished C. incanum and C. truncatum. Successful detection was achieved with a minimum of 1 pg DNA. The duplex assays rapidly and effectively identified more than 200 Colletotrichum isolates collected from soybean. An inoculation technique for evaluating soybeans for anthracnose resistance was optimized based on experiments to determine the type of inoculum (conidia vs. mycelia), duration of wetness of inoculated plants, and the age of inoculated plants. This technique was used to reevaluate previously reported anthracnose resistant soybean genotypes and a set of ancestral genotypes of modern day soybean cultivars. In the re-evaluation test of previously assessed soybean genotypes, Mandarin, Mandarin 507, and Mandarin (Ottawa) showed greater resistance than the other genotypes. Among the 14 ancestral lines tested, Mandarin had lowest disease rating, although it did not differ from Mandarin (Ottawa), CNS, Roanoke, Richland, and Mukden.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Yang, Hui-Ching

Contributors dc:contributor

• Hartman, Glen L.
• Zhao, Youfu
• Domier, Leslie L.
• Kent, Angela D.

• soybean anthracnose
• Colletotrichum species
• real-time polymerase chain reaction (PCR)
• soybean genotypes for anthracnose resistance

Statement dc:rights

• Copyright 2013 Hui-Ching Yang

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/46841

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/46841