Microbes in soil can work with plants to fight off disease

http://www.the-scientist.com/?articles.view/articleNo/33703/title/Fighting-Microbes-with-Microbes/

It is a very interesting article, albeit long. A summary:

There are 30,000 species of microbes in soil samples, vs 10K in humans. Current ag methods kill most but not all microbes, creating a vacuum for opportunistics.

Tomato plants communicate via a fungal network in the soil. Infected plants grown in the presence of this fungus warn neighbors about the disease, inducing the plant to produce disease fighting proteins.

A beneficial bacteria B subtilis establishes itself in the soil by blocking plant defenses, producing an antimicrobial at the same time, which may protect the plants roots while it is establishing. Other plants that were infected with bad bacteria Pseudomonas produced a sugar food source for B subtilis to encourage it's colonization of the roots. This triggered the plant to produce defensive chemicals. They worked together! Progeny of plants that were grown with B subtilis had better defense systems even if B subtilis wasn't around - it lasts across generations.

Plants grown under drought conditions had more bacteria that enhance growth and photosynthesis, enabling the plant to better withstand drought.

In infected plants, B subtilis colonization induced the plant to close its stomata (the pores in the leaves that allow gas exchange), which would prevent further infection (this particular disease can enter the plant through the stomata).

Microbial communities that were more genetically distinct resisted establishment of pathogens better - there was no niche for the pathogen. However, some communities with "too many" species were less able to ward off pathogens - they were not working synergistically in this case. You can imagine there may be a way to encourage certain beneficial microbial communities to best help the plant.

Of the plots sampled, a plot planted with a mixture of grasses and herbs had the strongest microbial community for fighting off disease.

You can draw a comparison between using antibiotics and the effect on your gut microbes, and the use of fungicides and insecticides on the soil microbes. Studies suggest that crop rotation, tilling and fertilizing are better ways to establish a strong soil microbial community.

Rapeseed seed meal can help beneficial bacteria streptomyces colonize soil and prevent root rot and help the plant grow as much as introducing streptomyces itself. A combination of seedmeals was better able to resist colonization by pathogens, because they contain different glucosinolates that break down, producing a variety of anti pathogen chemicals.

Cultivating healthy soil and hence, microbial communities, can help plants reduce disease, growing better, and curtailing the reliance on blunt-force chemicals.

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I think this research is very interesting because it shows how little we understand about nature. I am not a fan of the cover-all techniques we use in a lot of modern science and I think science is really going to move in the direction of using what nature has already provided via microbes. Microbes are the next big thing!