Dissemination of Goss’s Wilt of Corn and Epiphytic Clavibacter michiganensis subsp. nebraskensis from Inoculum Point Sources

Abstract

Goss’s wilt of corn, caused by Clavibacter michiganensis subsp. nebraskensis, has reemerged since 2006 as an economically important disease of corn in in the Midwestern United States. In 2012 and 2013, field plot studies were conducted with a pathogenic, rifampicin-resistant C. michiganensis subsp. nebraskensis isolate and a Goss’s wilt-susceptible corn hybrid to monitor epiphytic C. michiganensis subsp. nebraskensis population densities and the temporal and spatial spread of Goss’s wilt incidence originating from inoculum point sources. The randomized complete block trial included three treatments: noninoculated control, inoculum point sources established by wound inoculation, and inoculum point sources consisting of C. michiganensis subsp. nebraskensis-infested corn residue. Epiphytic C. michiganensis subsp. nebraskensis was detected on asymptomatic corn leaves collected up to 2.5 m away from inoculum sources at 15 days after inoculation in both years. The percentage of asymptomatic leaf samples on which epiphytic C. michiganensis subsp. nebraskensis was detected increased until mid-August in both years, and reached 90, 55, and 35% in wound-, residue-, and noninoculated plots, respectively, in 2012; and 50, 11, and 2%, respectively, in 2013. Although both growing seasons were drier than normal, Goss’s wilt incidence increased over time and space from all C. michiganensis subsp. nebraskensis point sources. Plots infested with C. michiganensis subsp. nebraskensis residue had final Goss’s wilt incidence of 7.5 and 1.8% in 2012 and 2013, respectively; plots with a wound-inoculated source had final Goss’s wilt incidence of 16.6 and 14.0% in 2012 and 2013, respectively. Our findings suggest that relatively recent outbreaks of Goss’s wilt in new regions of the United States may be the result of a gradual, nondetected buildup of C. michiganensis subsp. nebraskensis inoculum in fields.

Clavibacter nebraskensis causing Goss's wilt of maize: Five decades of detaining the enemy in the New World

“…C. nebraskensis survives epiphytically on symptomless maize leaves and it is possible that populations build up gradually over time in new areas before disease is detected (Eggenberger et al, 2016).…”

Corn disease update

“…Moreover, these alternate weeds likely enable the bacterium to become endemic to Iowa. Research from the Robertson lab has demonstrated that Cmn can be dispersed from point sources of inoculum such as a piece of Cmn-infested residue or an infected weed and colonize the leaves of corn seedlings season after emergence (Eggenberger et al 2016). This epiphytic population of Cmn on corn leaves gradually increases and disease occurs later in the season.…”

Goss’s Wilt Resistance in Corn Is Mediated via Salicylic Acid and Programmed Cell Death but Not Jasmonic Acid Pathways

“…With the increased demand for corn and corn products, there is an increased demand for more corn acres. This leads to tighter corn rotations and an increase in the incidence of corn diseases such as Goss’s wilt, which is triggered by the bacterial pathogen Clavibacter nebraskensis ( Cn ) [ 2 ]. This highly damaging Gram-positive bacterium grows as orange-colored colonies in agar culture media [ 3 , 4 ] and is part of a super-group of bacteria within the genus Clavibacter that infect a variety of other crops [ 3 , 5 , 6 , 7 ].…”

“…This highly damaging Gram-positive bacterium grows as orange-colored colonies in agar culture media [ 3 , 4 ] and is part of a super-group of bacteria within the genus Clavibacter that infect a variety of other crops [ 3 , 5 , 6 , 7 ]. Goss’s wilt has reached every state in the U.S. corn belt and every Canadian province with a significant corn production, and it has been on the rise since the adoption of glyphosate as the main method of weed control instead of conventional tillage [ 2 , 8 , 9 , 10 , 11 ]. Depending on where Cn enters the plant, it can cause either corn wilt or blight [ 8 , 9 , 12 , 13 ].…”