Seed Endophytes of Smooth Crabgrass (Digitaria ischaemum) Increase White Clover (Trifolium repens) and Dandelion (Taraxacum officinale) Seedling Mortality.

The objective of our research was to determine if smooth crabgrass (Digitaria ischaemum (Schreb.) Schreb. ex Muhl.) seed contains endophytes that antagonize competitor plants. Smooth crabgrass seeds harvested in November 2016 from North Brunswick, NJ were surface sterilized by continuous agitation in a 4% sodium hypochlorite solution for 40 minutes. Seeds were rinsed with sterile water and placed on various media to culture surviving fungi and bacteria. After 4-6 days of incubation at 22±2 ^oC, outgrowing fungi and bacteria from seeds were isolated. This sterilization and culture process was repeated on three separate occasions. Sixteen bacterial isolates were collected and inoculated onto previously surface disinfected seeds of dandelion (Taraxacum officinale [Taraxacum officinale (L.) Weber ex F.H. Wigg] and white clover (Trifolium repens L.) to evaluate their effects on seedling mortality in Petri dish culture. Certain bacterial isolates resulted in >80% mortality of white clover seedlings at 2 weeks after emergence. These isolates increased mortality of dandelion seedlings as well. A seed endophyte isolated from Phragmites australis seed was included in the experiments as a standard and caused 0% white clover seedling mortality. Mortality of seedlings of non-treated sterilized seed was <5%. Colonization of bacteria into root cells was determined by microscopic observation with ROS staining using diamino benzidine (DAB) and will also be presented.