Suppressive Soils • Soil microfauna effect • Destroy soil-borne pathogens –(e.g. take-all of wheat after years without rotation) • Destroy weed seeds –(e.g. soils from European weed place of origin 30-40% more weed suppressive than PNW soils) • Destroy soil-dwelling arthropods –(e.g. entomopathogenic nematodes).
http://organic.kysu.edu/SuppressiveSoil.pdf
Abstract. To determine the factors affecting the germination, early germ-tube growth (collectively called ‘germination’) of chlamydospores of Fusarium oxysporum f. sp. cubense and the severity of Fusarium wilt in banana plantlets, we varied chemical and physical factors in a suppressive and conducive soil.
http://www.sciencedirect.com/science/article/pii/S0038071799000450
A physical process, most likely diffusion of a nutrient or substance that supports germination, may limit germination of chlamydospores in the suppressive soil. This is supported by the different response of chlamydospore germination to temperature in the two soils.
http://www.sciencedirect.com/science/article/pii/S0038071799000450
To return the favor, the sugar beets funnel about a fifth of their photosynthetically captured carbon through their roots into the soil to fuel the microbes. New research reveals that it takes a community of soil microbes, not just one or two, to protect crops. The top image is a healthy sugar beet field.
http://newscenter.lbl.gov/2011/05/05/community-soil-microbes/
Many factors determine whether or not symptoms of Fusarium wilt are expressed, not the least of which is the behaviour of Foc in the soil. An important measure of this behaviour is the germination of chlamydospores and the early growth of germ tubes.
http://www.sciencedirect.com/science/article/pii/S0038071799000450
The effect of soil pH on the germination of chlamydospores of Fusarium oxysporum f. sp. cubense (closed symbols) and the expression of disease severity in banana plantlets in a suppressive and a conducive soil. Vertical bars are standard errors.
http://www.sciencedirect.com/science/article/pii/S0038071799000450
Fusarium suppression • Fusarium wilt held off by suppressive soil, but not peat • Effect lost with sterilization • Somewhat restored by inoculating with Trichoderma or Fo47 (non-pathogenic Fusarium strain) Cotxarreraa et al.
http://organic.kysu.edu/SuppressiveSoil.pdf
2. Most suppressive soils lose their disease suppressive capability when pasteurized (in other words exposed to high temperatures; 80 o C in this paper). Disease suppressiveness is transferable from a suppressive soil to a disease-conducive (non-suppressive) soil by mixing them together. These results indicate the microbial nature of the suppressiveness of the soil in this study.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14787
Science 332: 1097. • Plant pathogenic microbes damage plants • Beneficial microbes promote plant growth or inhibit pathogens • Most soil microbes don’t affect plants directly, but interact with other microbes Berendsen et al. 2012. The rhizosphere microbiome and plant health.
http://organic.kysu.edu/SuppressiveSoil.pdf
1. The soil investigated in this study was suppressive, but this only came about after years of being severely affected by the fungal pathogen, Rhizoctonia solani. Consistent with previous research, disease outbreaks are essential to get a suppressive soil – to gain immunity you have to get sick first. 2.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14787
what is a disease-suppressive soil?
Disease suppressiveness is transferable from a suppressive soil to a disease-conducive or non-suppressive soil by mixing them together.