Limiting Populations and Spread of Clavibacter michiganensis subsp. michiganensis on Seedling Tomatoes in the Greenhouse

Abstract

Symptomless greenhouse tomato transplants may harbor high populations of Clavibacter michiganensis subsp. michiganensis, the causal agent of bacterial canker, leading to yield loss in the field. The objective of this study was to determine whether resistant cultivars, acibenzolar-S-methyl, avirulent strains of C. michiganensis subsp. michiganensis, or standard bactericides reduce pathogen populations and spread among greenhouse tomato seedlings. All treatments limited pathogen populations compared with the untreated inoculated susceptible cultivar in 1996 and 1998, but not in 1997. In 1996, copper hydroxide alone or mixed with mancozeb or streptomycin limited pathogen populations relative to acibenzolar-S-methyl, acibenzolar-S-methyl mixed with copper hydroxide, and avirulent strains. Copper hydroxide mixed with streptomycin limited pathogen populations compared with copper hydroxide mixed with mancozeb. Adding copper hydroxide to acibenzolar-S-methyl limited pathogen populations compared with acibenzolar-S-methyl alone. In 1998, treatments did not differ significantly from each other in limiting pathogen populations. The treatments limited spread of the bacterium only in 1997. Copper hydroxide mixed with mancozeb limited spread compared with copper hydroxide mixed with streptomycin. Pathogen spread was also reduced among resistant cultivars compared with the susceptible cultivar treated with streptomycin. In the field, the untreated inoculated susceptible cultivar produced yields that were 61% (1996) and 93% (1997) of those produced by the uninoculated susceptible cultivar. Fruit spotting occurred regardless of treatment. To prevent severe bacterial canker disease in the field, growers should initiate and sustain bactericide applications to tomato transplants while in the greenhouse to suppress pathogen populations. Cultivar resistance and acibenzolar-S-methyl may be helpful in disease management of bacterial canker on tomato.

Effects of copper-based compounds, antibiotics and a plant activator on population sizes and spread of Clavibacter michiganensis subsp. michiganensis in greenhouse tomato seedlings

“…michiganensis in all three sampling regions (a, b and c), and also completely stopped pathogen spread in the most distant region, confirming the findings of Hausbeck et al (2000) and Werner et al (2002), this antibiotic was included in our trials only as a standard. However, regardless of the excellent effects of streptomycin, application of this compound is banned in most European countries, including Serbia, and it is forbidden even in the USA in greenhouse conditions and therefore cannot be recommended for use.…”

“…Although C. michiganensis subsp. michiganensis strains resistant to copper compounds have not been reported yet, which was also confirmed in our previous studies (Milijašević, 2008), bacterial canker management programs that are not entirely reliant on copper compounds are favored (Werner et al, 2002).…”

“…Recent studies of the efficacy of ASM in limiting populations and spread of C. michiganensis subsp. michiganensis have shown that this compound may be helpful in disease management of tomato bacterial canker, especially when combined with copper-hydroxide and resistant cultivars (Werner et al, 2002). In similar experiments, Baysal et al (2003) reported a reduction in disease severity (up to 76.3%) in plants pretreated with ASM, and enchancement of resistance of ASM-treated plants associated with significant increases in the activities of POX and chitinase.…”

“…Recent studies have confirmed that application of copper-based bactericides on tomato seedlings in the greenhouse reduce population sizes and spread of C. michiganensis subsp. michiganensis and impact plant development and yield in the field (Hausbeck et al, 2000;Werner et al, 2002). However, long term use of these bactericides may lead to occurrences of copper-resistant bacterial strains (Cooksey, 1990).…”

“…In spite of the fact that C. michiganensis subsp. michiganensis strains resistant to copper compounds and antibiotics have not yet been reported, disease management programs that are not wholly reliant on copper compounds are desirable (Werner et al, 2002).…”