Seed transmitted endophytes of crop wild relatives

Crop wild relatives have potential to provide improved genetic traits (biotic and abiotic stress resistance) through breeding with closely related domesticated crop species. In addition to the introgression of genetic traits, crop wild relatives could represent a source of beneficial symbionts that may improve crop productivity. Grasslands provide sources of many crop wild relatives and are among the largest and most widely distributed ecosystem representing 26% of the world land area. Grasses from the subfamily Pooideae are often infected with endophytic Epichloë species that represent dominant members of the plant’s microbiome and provide protection to their host from biotic and abiotic stresses. Although Epichloë species associate with many crop wild relatives, these endophytes are not found within domesticated cereal crops such as wheat or rye. We examined wildryes from North America and Hordeum species from Asia to identify seed transmitted endophytes that could be utilized for improving cereal crops. Using PCR to detect presence or absence of genes encoding bioactive alkaloid biosynthesis steps, mating type genes and other informative markers, we identified endophyte infected host lines and determined the endophyte taxa and diversity associated within each host species. Scanning electron microscopy and confocal laser scanning microscopy were used to examine the endophyte colonization patterns. We observed some host species had epiphytically growing mycelia, conidiogenous cells and conidia on the leaf surface in addition to the endophytic intercellular growth. Synthetic associations of wheat and rye with the endophytes from Hordeum species could be established but endophyte compatibility was poor resulting in severely stunted and developmentally delayed host plants. Yet, epiphyllous hyphae could be observed on the infected rye and wheat blades similarly to what is seen in the native host. Understanding mechanisms of endophyte host compatibility may provide insight to overcome the barriers of moving Epichloë species to domesticated cereal crops.