b'Even if its a short-term gain, thats a critical gain, says Dangl.That said, were not yet at the point of most biologicals persisting in the soil and delivering long-term benefit. In other words, even if a biological offers proven efficacy in theory, it may lack return on investment in practice, Dangl says.If you think about biologicals for things like fungal control, you may end up spraying 10 times a season because the bacteriaeven if theyre very effective at enhancing fungal resistancesimply dont make it long enough to give you the protection that you need, Dangl says.Engineered SolutionsWhile biologicals are generally formulated products of selected microorganisms or compounds that are applied to the soil, foli-age or seed with the intention of changing the existing microbi-ome, another stream of related research focuses on harnessing and leveraging naturally occurring microbial communities. Some researchers have approached that concept as anJan Leach, the associate dean for research at Colorado State engineering problemessentially gluing a specific microbe toUniversitys College of Agricultural Sciences.a root biochemically. Beginning in the 1990s, French researcher Yves Dessaux and his colleagues designed plants that secretedThe drought-stricken plants look terrible, Dangl says. specific sugars, then engineered a bacterium that depended onTheyre about one third the size of control plants. Then we take those sugars but couldnt produce them on its own. This createdour collection of bacteriamaybe 20 or 30 strains, all of which a symbiotic relationship where the bacterium had to colonize theare isolated from various soils but are the same genotype [of plant roots to survive, showcasing a sophisticated example ofbacteria] and from the same [crop cultivar]and we treat the how plants and microbes can be engineered to cooperate. sick plants with the microbes. Our goal is to find a specific strain In the three decades since then, significant work has beenthat rescues these terrible, ugly plants back to a quasi-normal done on microbial engineering to customize microbial communi- plant. Were trying to find effective strains that are already ties to create designer seed microbiomes. By identifying specificadapted to the host. microbes that perform critical functions like nutrient solubiliza-He says finding effective strains for individual cultivars is tion or pathogen suppression, researchers are finding ways toabsolutely do-able. Thats the good news. engineer seeds to recruit these beneficial microorganisms in aThe not so good news is that a strain that proves a game-targeted manner. This approach could lead to crops that arechanger in one cultivar may fall entirely flat in another cultivar. He naturally more resilient to environmental stresses, includingadmits its a daunting challenge.drought and salinity. Theres a lot more to understand before thisSo now imagine youre a wheat farmer and you want a pathway to leveraging the microbiome can be more fully utilized,biological to control fungal infection, drought or another issue. says Leach. You may need a particular strain for your cultivar. And its more Were beginning to understand things about what the plantthan that, because the endogenous community is different from produces that attracts a good, healthy microbiome and what wefield to field. So what works in one field may fail in another under might be able to manipulate in the plants so that, for example,certain conditions.their roots will attract beneficial microbes and repel non-benefi-cial ones, she says. Changing a plant is pretty complex becauseWhats Aheadit takes many genes to make the chemicals they secrete, whichAt this point, science is only able to deliver single microbes that governs that microbiome recruitment. I expect, though, thatinteract with plants in beneficial ways. Leach says the future is probably within the next 10 years well have huge progress in thisabout understanding how multiple microbes work in concert area, maybe five years even.and community with each other and with plants to deliver much bigger and longer lasting benefit.Bacterial RecruitmentOne thing is certain in plant microbiome research: the future Instead of trying to force-fit bacteria to new environments oris coming fast. While big unknowns currently remain, Dangl has engineer plant-bacteria relationships, Dangls team is focused onconfidence that manipulating bacteria will play a rapidly increas-this kind of natural recruitment of microbes. He and his teaming role in agricultural production.are searching for specific strains of naturally occurring bacteriaWhen we started this lab about 15 years ago, weand I that offer drought resistance and, rather than being a foreignmean the research communityreally didnt know anything introduction, already exist in conjunction with individual crop[about the microbiomes interaction with plants], Dangl says. cultivars. The amount of new, truly fundamental knowledge is incredible, Using researchers favorite R&D plant, Arabidopsis, on agarand that is just going to increase. Were on a steep, steep upward plates in the lab, they start by mimicking a drought environment.climb in knowledge. SW88/ SEEDWORLD.COMDECEMBER 2024'