LB 6-50 - Characterization of the Eastern Joshua tree arbuscular mycorrhizal community

Background/Question/Methods:

The 2020 Dome Fire in the California Mojave Desert burned through the Cima Dome, killing over a million Eastern Joshua trees (Yucca jaegeriana). The Cima Dome had been modeled as a critical climate refuge, therefore, replanting efforts have already begun. Several aboveground methods of ensuring replanted seedling survival are being tested by land managers. Arbuscular mycorrhizal fungi (AMF) are commonly found inhabiting the roots of desert plants, since they greatly increase water and mineral uptake. AMF inoculation may be necessary to improve Y. jaegeriana regeneration since the shrubs that act as nurse plants and possible sources of AMF inoculum were practically wiped out within the burn scar. The AMF community of Y. jaegeriana has never been characterized, and there is only one study characterizing the AMF of its sister genus Y. brevifolia. To provide this baseline information, we carried out seasonal sampling of roots and soil from twenty healthy Y. jaegeriana. We have thus far used Illumina MiSeq sequencing of the 18S rRNA region using the WANDA-AML2 primer pair and visual confirmation through spore counting of desert soil for summer, fall, and winter.

Results/Conclusions:

We identified 420 amplicon sequence variants, representing 29 distinct virtual taxa of AMF from 73 root and soil samples. The most abundant taxon, Glomus sp. VTX00400, was detected in every soil and root sample. We found 7 AMF families including Glomeraceae, Claroideoglomeraceae, Acaulosporaceae, Paraglomeraceae, Diversisporaceae, and Gigasporaceae listed in descending order of both relative sequence abundance and sample frequency. On average, we found 4.1 ± 0.44 (mean ± standard error) AMF taxa in soil samples, compared to 1.96 ± 0.15 in root samples. While richness did not significantly vary across our summer, fall, and winter timepoints, there was significant compositional turnover among seasons. We recovered the largest root AMF diversity in fall, with 12 taxa, versus 8 taxa found in the winter and spring roots. Root AMF turnover occurred throughout the seasons with only 2 taxa found in all 3 seasons. Indeed, 5 root AMF taxa were unique to the fall, 2 to winter, and 3 to summer. While we were unable to recover AMF from winter soils, we found 15 AMF taxa in summer and 14 in fall soils with only 9 taxa shared between the seasons and 6 unique to the summer and 5 taxa unique to fall.