Baldcypress trees (Taxodium distichum) play a critical role in coastal Louisiana due to their resistance to wind and storm surge. However, the recruitment of baldcypress saplings has been nonexistent in recent years. An important group of organisms that may offer insights into the decline of the species in Louisiana are endophytes (microscopic fungi and bacteria that live in plant tissues without causing disease). As symbionts, endophytes can enable their plant hosts to better tolerate stressful environments, pathogens, and herbivory. A recent survey of such endophytic communities in baldcypress uncovered that more than 50% of the fungi consisted of Eutypa lata, a pathogen that is considered a major threat to commercial grapes and many other crops. No study to date has investigated whether E. lata is endophytic or pathogenic to baldcypress. To this end, we sought to investigate how E. lata impacts the growth and development of baldcypress seedlings by inoculating the roots of seedlings with varying concentrations of E. lata and measuring changes in plant growth and health. The effectiveness of the inoculation was evaluated by plating surface-sterilized root pieces on agar and determining which pieces grew fungi morphologically identifiable as E. lata.
Results/Conclusions
The overall growth of the seedlings (quantified using PCA) was not affected by the concentration of E. lata inoculum (linear regression, p = 0.35). Likewise, mortality was rare (~8% of plants) and did not differ significantly among treatments (Fisher’s exact, p = 0.89). Within the roots, E. lata was abundant – even in the control group – but its abundance increased significantly with inoculum concentration (logistic regression, p < 0.01). These results indicate that E. lata is unlikely to retard the growth and development of baldcypress seedlings and that the observed strain is endophytic in baldcypress, rather than pathogenic. This work also highlights the importance of developing experimental methods for ascertaining whether common members of the root microbiome community are acting for the benefit or detriment of the host plant.