Complex associations between cross‐kingdom microbial endophytes and host genotype in ash dieback disease dynamics

Tree pathogens are a major threat to forest ecosystems. Conservation management strategies can exploit natural mechanisms of resistance, such as tree genotype and host‐associated microbial communities. However, fungal and bacterial communities are rarely looked at in the same framework, particularly in conjunction with host genotype. Here, we explore these relationships and their influence on ash dieback disease, caused by the pathogen Hymenoscyphus fraxineus, in European common ash trees. We collected leaves from UK ash trees and used microsatellite markers to genotype trees, qPCR to quantify H. fraxineus infection load, and ITS and 16S rRNA amplicon sequencing to identify fungal and bacterial communities, respectively. There was a significant association between H. fraxineus infection intensity and ash leaf fungal and bacterial community composition. Higher infection levels were positively correlated with fungal community alpha diversity, and a number of fungal and bacterial genera were significantly associated with infection presence and intensity. Under higher infection loads, leaf microbial networks were characterised by stronger associations between fewer members than those associated with lower infection levels. Together these results suggest that H. fraxineus disrupts stable endophyte communities after a particular infection threshold is reached, and may enable proliferation of opportunistic microbes. We identified three microbial genera associated with an absence of infection, potentially indicating an antagonistic relationship with H. fraxineus that could be utilised in the development of anti‐pathogen treatments. Host genotype did not directly affect infection, but did significantly affect leaf fungal community composition. Thus, host genotype could have the potential to indirectly affect disease susceptibility through genotype x microbiome interactions, and should be considered when selectively breeding trees. Synthesis. We show the diversity, composition and network structure of ash leaf microbial communities are associated with the severity of infection from ash dieback disease, with evidence of disease‐induced dysbiosis. We also show that host genotype influences leaf fungal community composition, but does not directly influence tree infection. These findings help to elucidate relationships between host genetics, the microbiome, and a tree pathogen, highlighting potential resistance mechanisms and possible co‐infection concerns that could inform ash tree manage ment

Long-term preservation of Lotus tenuis adventitious buds

Encapsulation-dehydration, encapsulation-vitrification, and vitrification were tested for cryopreservation of Lotus tenuis (Fagaceae) adventitious buds clusters (ABCs) obtained by a direct regeneration system from leaves cultures. Among them, the PVS3-based vitrification procedure was found to be useful for survival and regrowth of the preserved explants. For vitrification, the ABCs were dehydrated in a solution containing 2 M glycerol + 0.4 M sucrose for 25 min at room temperature, submerged in PVS3 solution for 1 h at 0 °C, then immersed in liquid nitrogen for 48 h and rapidly rewarmed. Afterword, the explants were unloaded in MS liquid medium with 1.2 M sucrose for 30 min. The washed tissues were dried superficially on filter paper and cultured in semisolid hormone-free MS medium containing 0.1 M sucrose. All cultures were maintained at 25 °C in the dark for 10 days and transferred to the light conditions. With this procedure, 79 ± 5.3% survival and more than 80% of the plantlets displaying a phenotype similar to the non-treated control after acclimatization. The data settled from ISSR showed no genetic dissimilarities between in vitro regenerants derived from cryopreserved tissues and the non-treated plants. Thus, our results indicate that the use of vitrification-based PVS3 solution offers a simple, accurate, and appropriate procedure for the cryopreservation of L. tenuis adventitious buds.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Espasandin, Fabiana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Brugnoli, Elsa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Ayala, Paula G. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Ayala, Lilian P. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Ruiz, Oscar Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Sansberro, Pedro Alfonso. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin