Effects of salinity on baldcypress (Taxodium distichum) endophytes

Background/Question/Methods

Baldcypress trees (Taxodium distichum) are crucial to the Gulf Coast region as major buffers against storm damage and are a key restoration species. Unfortunately, sea level rise and associated increases in salinity are degrading cypress swamps throughout Southern Louisiana into marsh and open water. Changing environmental conditions, such as increased salinity, can disturb symbiotic associations. Our study examines a key group of symbionts, the endophytes, which are microscopic fungi and bacteria that live entirely within the tissues of their host plants. Endophytes have been found throughout all tissues of all plants examined to date and in some cases have been shown to confer competitive advantages to their host plant such as increased resilience to salt stress.

In October 2014, we sampled leaves and roots from twelve trees at four sites in Southern Louisiana. Three sites were fresh water, and one site was a brackish, degraded site. We then isolated endophytes into pure culture to begin the process of characterizing the diverse bacterial and fungal endophytes present in baldcypress trees.

Results/Conclusions

We sampled from a total of 48 baldcypress trees and cultured 364 isolates of fungal and bacterial endophytes with 208 preliminary morphotypes. Abundance of bacteria and fungi in roots differed significantly with respect to site with fewer endophytes in the salt-water degraded site.  These results suggest that increases in salinity correlate negatively with endophyte diversity and abundance in baldcypress trees. Future experiments will need to investigate the functions of endophytes in this key restoration species.