b'ing with their neighbors bying up pathway A while thethem nearly impossible todistinct microbiotas. trading food, removing toxicstrain that is increasing leafstudy in isolation in the labora- Jos Raaijmakers of the waste and sending signalssize is turning up pathway Btory, which is how microbiolo- Netherlands Institute of about changes in the soilbut is also changing pathwaygists have typically figured outEcology and his colleagues around them.A. These are not necessar- how different microbes work.recently identified a shift in Historically, we have clas- ily independent events andIsolated from the other soilthe structure of the microbi-sified microbes as beneficialthe results are not necessarilymicrobes they normally inter- ome of modern and ances-or as pathogens with respectadditive. You have to do a lotact with, microbes broughttral varieties of common to how they interact withof work selecting your strainsinto a sterile test tube maybean (Phaseolus vulgaris); the plant, Cadle-Davidsonand your strain combinationssimply die. Davide Bulgarelli,Bacteroidetes were more observes. But now we haveto understand the host planta principal investigator at theabundant in wild relatives, learned that is not always true.to get a product that per- University of Dundee in theand their contribution to the The combination of microbesforms in the field. United Kingdom, describescommunity was progressively is not always additive. If youthis microbial interconnected- replaced by Actinobacteria know that one strain of anness with a 1934 quote fromand Alphaproteobacteria in organism increases rootLourens Gerhard Marinus Baasthe more domesticated plants.growth and another strainBecking, a Dutch botanist and How do these differ-increases plant growth andEverything ismicrobiologist: Everything isences alter the functionality biomass, you do not neces- everywhere, but the environ- of the microbiome? Thanks sarily get something that haseverywhere, but thement selects. to the experience gained by both big roots and big leaves.environment selects.Bulgarelli suggests char- Arabidopsis researchers, sci-That is what you hope for, butacterizing the plant micro- entists are now in a position to that is not what always hap-L ourens Gerhard Marinus biome and its function canaddress this question.pens. The complexity is theBaas Becking be applied in an agriculturalThe idea that plants other microbes also present insetting, equipping the cropsshape the cocktail of bacteria, the microbiome. to grow better in resource- archaea, and other microbes Another factor is how thepoor environments and toattracted to their roots is dec-plant is responding. This isfight off dangerous patho- ades old. The concept of soil true of a lot of the productsThe catch is that withoutgens. One strategy manyfatigue, for example, comes out therethe microbesknowing what each microbecompanies are pursuing is afrom observations of plants interact with the plant andin the soil does, it is nearlyform of plant probiotic, whichattracting soil pathogens that cause changes in geneimpossible to decide whichconsists of preparations ofbecome more abundant over expression. The changesmicrobes to add or subtract tobeneficial microbes to besuccessive growing seasons will cause some genes tomaximize crop yields. Addingmixed with seeds at planting.of the same crop, explains express at a higher levelor removing the wrong typesAnother approach is to useVenkatesan Sundaresan, and turn up some biologicalof microbes could upset theplant breeding to select forUniversity of California, Davis, pathways while others maydelicate balance of the com- varieties that have enhancedplant biologist. Eventually, be turned down. In a plantmunity, with disastrous resultssymbiosis with the microbiota.agricultural productivity falls. as with humans, all biologi- for plant growth and cropMany questions remain aboutThe soil changes dont neces-cal pathways interact withyields. As a result, scientiststhe plant microbiome, notsarily benefit the crop, even each other. If you turn up onemust understand not just theleast of which is how thou- though the crop is manipu-pathway, you are also affect- microbes that directly affectsands of years of cultivationlating the soil. Contrary to ing the other one withoutplant growth and soil health,have changed crops relation- expectations, we found that having intentionally affectedbut also all of the surroundingships with the soil biota. Usingplants grown in sterile clay it. The idea of trying to getmicrobes that play an indirecta cultivation-independentand inoculated with microbes an additive effect is reallyrole in supporting the entireapproach, scientists havefrom another kind of soil, grew challenging because it couldmicrobial community. determined that wild ances- faster with microbes from turn out that the strain that isIt is the interconnectednesstors and modern varieties ofwild soils, and slower with increasing root growth is turn- of soil microbes that makesbarley (Hordeum vulgare) hostmicrobes from cultivated soils. JANUARY 2020SEEDWORLD.COM /53'