Investigation of Alternative Hosts and Agronomic Factors Affecting Xanthomonas vasicola pv. vasculorum, Causal Agent of Bacterial Leaf Streak of Corn

Authors

Terra Marie Hartman, University of Nebraska-LincolnFollow

First Advisor

Tamra Jackson-Ziems

Date of this Version

11-2018

Citation

Hartman, T. M. 2018. Investigation of Alternative Hosts and Agronomic Factors Affecting Xanthomonas vasicola pv. vasculorum, Causal Agent of Bacterial Leaf Streak of Corn. MS thesis, University of Nebraska.

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Tamra Jackson-Ziems. Lincoln, Nebraska: November, 2018.

Copyright (c) 2018 Terra Marie Hartman

Abstract

Xanthomonas vasicola pv. vasculorum, causal agent of bacterial leaf streak of corn, was first reported in the U.S. in 2016 on Nebraska corn leaf samples. Prior to this report, the pathogen had only been reported on corn in South Africa. After the Nebraska report, the pathogen was reported on corn in Argentina, Brazil, and several U.S. states. This pathogen has an extensive host range, which includes sugarcane (Saccharum officinarum), grain sorghum (Sorghum bicolor), palm species (Dictyosperma album, Roystonea regia, and Areca catechu) and broom bamboo (Thysanolaena maxima). Plants commonly found in the U.S. had not been evaluated as alternative hosts. Additionally, the distribution of X. vasicola pv. vasculorum in Nebraska and agronomic factors that influence its survival had not been investigated. A survey was conducted to determine the pathogen’s distribution, and to better understand agronomic factors that may influence disease. Respondents submitted a symptomatic leaf sample for pathogen confirmation with their completed survey. The pathogen was confirmed in 74 Nebraska counties via a PCR assay. Survey results indicated that the strongest predictors of a sample testing positive for X. vasicola pv. vasculorum included irrigation, planting date, crop rotation, tillage, and growth stage. A greenhouse experiment was conducted to examine U.S. plant species that could serve as alternative hosts for the pathogen. Hosts included oat (Avena sativa), rice (Oryza sativa), orchardgrass (Dactylis glomerata), indiangrass (Sorghastrum nutans), big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), timothy (Phleum pratense), sand bluestem (Andropogon hallii), green foxtail (Setaria viridis), bristly foxtail (Setaria verticillata), johnsongrass (Sorghum halepense), shattercane (Sorghum bicolor), yellow nutsedge (Cyperus esculentus), downy brome (Bromus tectorum), tall fescue (Festuca arundinacea), and western wheatgrass (Pascopyum smithii). A field study examined the potential for these plants to become infected by the pathogen in a natural environment. Host species were transplanted to a field naturally infested with X. vasicola pv. vasculorum. With natural inoculum, big bluestem and bristly foxtail displayed symptoms, and the pathogen was isolated from them. These results indicate that certain agronomic practices, as well as alternative hosts found in and near corn fields, may influence the survival of X. vasicola pv. vasculorum.

Advisor: Tamra Jackson-Ziems