Current agricultural practices on available arable land will not meet the nutritional needs of a population that will soon exceed nine billion people. In parallel, climate change is increasing extreme weather events, and continued urbanization of farmland is eliminating arable land. There is a clear need for sustainable agricultural innovations that can increase yields and provide food security while mitigating environmental degradation. In recent years interest has grown in harnessing the beneficial associations that soil microbes can form with plants to improve agricultural outcomes. The plant microbiome abounds with plant growth-promoting (PGP) bacteria that can help plants acquire more nutrients from the soil and tolerate stressors like drought. PGP bacteria can also control plant pathogens and promote interactions with other beneficial organisms. Finding ways to harness these beneficial microbes to improve crop growth and yield has the potential to ameliorate the challenges imposed by the world’s growing population and environmental degradation. However, several obstacles remain to using PGP-based strategies for agricultural improvement.
Three obstacles that we address in this project are: (1) Even within a single crop species, not all plant genotypes respond the same way to PGP bacterial applications. This indicates the existence of a genetic basis to how plants respond to PGP bacteria that must be understood in order to successfully use PGP applications on different crop varieties. (2) PGP microbial applications are extremely susceptible to microenvironmental variation; thus, achieving sufficiently uniform conditions, to test the effectiveness of an application poses a challenge. (3) PGP effects are often likely mediated through impacts on plant roots, but belowground responses to PGP-bacteria have traditionally been difficult to assess.
We have been developing the grass model species, Brachypodium distachyon, as an ideal plant system for screening and evaluation of PGP bacteria. As a species that is easily and rapidly grown in a laboratory setting and is closely related to wheat, rye, oats, barley, and several forage grasses, B. distachyon offers a screening system that is likely to ensure translation of findings to relevant crops. We have also developed a novel standardized growth system, termed “rhizotrons” to study the effect of PGP bacteria on above- and belowground plant phenotypes under high-throughput conditions. With these systems we have the following objectives:
Objective 1: Develop protocols and quantify the effects of a known PGP bacteria on belowground plant growth in a line of B. distachyon that allows for real time quantification of root architecture.
Objective 2: Assess the differential effect of this PGP bacteria on above-ground growth of several lines of B. distachyon that have been used.
Objective 3: Used a controlled cross of B. distachyon lines that differ in response to PGP application to identify genes controlling this response.
Our target audience is basic plant researchers seeking to understand mechanisms of pant growth and those seeking to create more sustainable crops. Our activities will lead to the outcomes described above through creation of protocols to quantify root growth, identification of B. distachyon lines that respond in a differential manner to PGP bacteria application, identification of plant growth traits that are more and less likely to be impacted by PGP microbes, and identification of candidate loci for plant genotype x PGP microbe response in B. distachyon. This will benefit our target audiences by providing research tools and knowledge that can be leveed for further gene discovery and by helping accelerate the discovery of similar genes in energy, cereal, and forage crops and ensuring translation of our findings to agriculture.