Submitted to: Nematropica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2001
Publication Date: N/A
Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plants, causing nine billion dollars in annual crop losses in the U.S. The problem addressed by this research is to find new ways of reducing crop losses caused by root-knot nematodes. For the study, bell pepper seeds and seedlings were treated with three beneficial microbes useful in biocontrol of plant diseases, particularly diseases that are caused by organisms in the soil. Two strains of a bacterium and one strain of a fungus were each applied to pepper seeds and to young plants. The bacteria and fungus were also applied as combinations. Plant-parasitic nematode populations were lowest with individual treatments of living beneficial microbes. Combinations of the bacteria and fungus did not decrease nematode numbers. Dead fungus treatment increased nematode numbers compared with most treatments. Plant vigor was not consistently affected by the treatments. The results are significant because they demonstrate that these microbes act against nematodes, and that adding the microbes as combinations decreases biocontrol effectiveness compared with applications of individual microbes. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: Bell pepper (Capsicum annuum L.) seeds and seedlings were treated with three beneficial microbes alone and in combination to determine their effects on root-knot nematode (Meloidogyne incognita) populations and on plant vigor. Individual treatments were viable and nonviable formulations of Burkholderia cepacia strains Bc-2 and Bc-F, and Trichoderma virens strain Gl-3 (applied as seed coatings and seedling drenches). Combination treatments were Bc-F/Gl-3, Bc-2/Gl-3, Bc-F/Bc-2, and Bc-F/Bc-2/Gl-3. At transplanting, seedlings were each inoculated with 10,000 M. incognita eggs or left uninoculated, and harvested 10 weeks later. Nonviable formulations were tested on inoculated plants only. No treatment consistently affected plant vigor. Numbers of egg+second-stage juveniles (J2 per g root were suppressed (P < 0.05) with Bc-2, Bc-F, and Gl-3 treatments, compared with untreated controls, but increased with nonviable Gl-3 treatment. The egg+J2 numbers recorded from combination treatments were not significantly different from untreated controls, suggesting that strain combinations decreased biocontrol effectiveness relative to applications of individual microbes.