Effects of Root Characteristics and Deep Tillage on the Development of Sudden Death Syndrome in Soybean

Current research on sudden death syndrome (SDS), caused by the fungus Fusarium solani f. sp. glycines (FSG) relies on foliar severity ratings as an indication of disease resistance. However, foliar symptom severity does not always correlate well with infection on the root system or with reductions in yield. A combination of root and foliar symptom severity ratings would provide more information on disease resistance. Yet, it is unknown whether physical mechanisms exist by which the root system of the soybean plant resists colonization or overcomes infection by this pathogen. Field experiments, conducted in Urbana, IL were designed to determine if root characteristics (architecture, length, surface area, volume, and average diameter), time and location of colonization, foliar disease severity, and yield varied among 12 soybean cultivars, and whether these parameters changed when plants were inoculated with FSG. Disease severity and yield of the cultivars were related to root characteristics. Significant differences in root characteristics, foliar symptom severity and yield were observed among the cultivars when inoculated with the pathogen. Resistant cultivars had significantly smaller root diameters and lower root volumes than susceptible cultivars. Colonization frequency on the upper taproot and laterals significantly changed throughout the season. However neither root colonization nor architecture was significantly different among cultivars. In addition, the effects of deep tillage on the severity of SDS, as measured by foliar symptoms and yield, were evaluated. Deep tillage did not significantly affect yield, nor did it decrease the amount of SDS observed as foliar disease symptoms. Yield and foliar symptom severity were significantly related, but the correlation was weak. In greenhouse experiments the effects of infection site on SDS disease severity and soybean root characteristics were evaluated. Soybean root length, surface area, and volume were significantly lower when the taproot was the primary site of infection compared to when the lateral roots were the point of infection. Results from field and greenhouse trials showed differences among the root characteristics of 12 cultivars, and that infection by FSG and the site of infection changed these root characteristics. This suggests that the soybean root system may play a role in SDS resistance.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Ortiz-Ribbing, Loretta Marie

Contributors dc:contributor

• Eastburn, Darin M.

• Agriculture, Agronomy

Language dc:language

eng

Identifier

(MiAaPQ)AAI3070403

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85005