Turfgrasses as model assay systems for high-throughput in planta screening of beneficial endophytes isolated from cereal crops

Abstract

Cereal crops including maize (Zea mays L.) are inhabited by non-disease causing microbes known as endophytes that can promote plant growth, aid in host nutrient acquisition and promote host pathogen resistance. Screening endophytes for beneficial traits in planta using large, slow-growing cereals is challenging, thus a rapid but relevant in planta system is needed. Here, we propose that turfgrasses can be used as high-throughput assay systems for screening cereal microbes for beneficial nutrient traits. Turfgrasses are genetic relatives of cereals, but small with fast growth rates; they can be grown in test tubes under sterile conditions on defined media. Five turfgrass genotypes were evaluated for traits ideal for assaying endophytes with nutrient acquisition traits. Based on these criteria, annual ryegrass (Lolium multiflorum) was selected as a high-throughput assay system. Annual ryegrass was then used to test a collection of maize endophytes for their ability to promote plant biomass in the absence of nitrogen. Out of 75 bacterial endophytes tested, one strain (an Enterobacter sp) consistently promoted root and shoot biomass. We discuss the potential of annual ryegrass as a model assay system to test cereal endophytes for acquisition of various nutrients, changes in root/shoot architecture as well as anti-pathogen traits.