Goss’s wilt and leaf blight of corn: chemical control, residue management and resistance

Mehl, Kelsey M

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https://hdl.handle.net/2142/88985 Copy

Description

Title

Goss’s wilt and leaf blight of corn: chemical control, residue management and resistance

Author(s)

Mehl, Kelsey M

Issue Date

2015-12-03

Director of Research (if dissertation) or Advisor (if thesis)

Bradley, Carl A.

Committee Member(s)

• Bohn, Martin
• Zhao, Youfu
• Pataky, Jerald K

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• maize
• Goss's wilt
• Clavibacter
• cultural control
• resistance

Abstract

Goss’s wilt and leaf blight of corn has been a re-emerging disease in the United States. Caused by the bacterium Clavibacter michiganensis subsp. nebraskensis (Cmn), Goss’s wilt has been increasing in Illinois due to factors that include continuous maize rotations, reduced tillage which increases debris harboring inoculum and the use of susceptible hybrids. There are several ways that could help control the spread of Goss’s wilt, including chemical control, residue management and the use of resistant hybrids. These three areas of control were the subject of this research. While there are resistant hybrids for some regions, the availability of resistant hybrids may be limited for other regions. In areas where Goss’s wilt was more severe, recommendations were provided to farmers to apply different products as “rescue treatments” even though there was no data to support or oppose them. This study was developed in order to understand the effect of various chemicals on Cmn and to see if it was a viable method of control while more resistant hybrids were being developed. A field study was done to evaluate the effect of copper hydroxide and citric acid on the severity of Goss’s wilt and on the yield of corn. Products were applied relative to inoculation with Cmn and were compared to inoculated, non-treated control. Non-inoculated treatments were also included. While treatments that were not inoculated with Cmn had significantly (P ≤ 0.05) lower Goss’s wilt severity compared with those that were inoculated, there was no significant differences among treatments within Cmn inoculated plots or within non-inoculated plots. Yield was reduced in Cmn-inoculated plots compared to the non-inoculated plots. Our research found that copper hydroxide and citric acid were not a viable management technique for Goss’s wilt. There is a current shift in farming practices in Illinois towards growing continuous maize without rotational crops. Cmn overwinters in corn debris, and increasing the debris left in the field could lead to epidemics. In order to understand the role of corn residue on the incidence and severity of Goss’s wilt, a field study was conducted in the summers of 2012 and 2013. Three different tillage methods were used on a field that historically has severe Goss’s wilt in order to vary the amount of residue left on the surface. These tillage methods included no-till, chisel plow and moldboard plow. Ten susceptible hybrids were evaluated for the incidence and severity of Goss’s wilt from natural infection. The incidence (%) and severity (0-9 scale) data were used to calculate a disease severity index (DSI), where DSI – (% incidence) X (severity) / 9. The different tillage treatments had a significant effect on both DSI (P = 0.0004) and yield (P = 0.0005). The no-till treatment resulted in the highest amount of residue and a significantly higher DSI than the other two treatments. The moldboard plow treatment had the lowest amount of residue left on the surface and had significantly lower DSI than no-till and chisel plow. These results have shown that by limiting the amount of infected corn residue left on the surface, Goss’s wilt may be managed. Resistant hybrids are limited in some regions of the United States. With the re-emergence of Goss’s wilt, more resistant hybrids are being developed for more areas. The University of Illinois plant pathology inbred collection has over 2,000 inbred lines collected from all over the world. This collection has been evaluated for other potential sources of resistance to other maize diseases such as Aspergillus ear rot (Aspergillus flavus) and grey leaf spot (Cercospora zeae-maydis). An initial screen was conducted near Urbana, IL in 2011. Over 1,500 inbred lines were screened, inoculated with a Cmn cell suspension and had the Goss’s wilt severity rated with a 1-9 severity scale, with a 1 = resistant and 9 = susceptible. Over 150 lines were identified to have potentially high levels of resistance to Goss’s wilt. These lines were moved to a second stage of screening in 2012. During the second stage, not all the lines preformed as well as the previous year. Nine lines were chosen to move to the final stage of screening. These nine lines had a mean severity score of 1.9, while the susceptible check had a mean score of 6.4. From our research, we found that there are potential sources of resistance to Goss’s wilt in the inbred collection that could be used for future breeding efforts.

Graduation Semester

2015-12

Type of Resource

text

Permalink

http://hdl.handle.net/2142/88985

Copyright and License Information

Copyright 2015 Kelsey Mehl

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