Heritable microbiome variation is correlated with source environment in locally adapted maize varieties.

Beneficial interactions with microorganisms are pivotal for crop performance and resilience. However, it remains unclear how heritable the microbiome is with respect to the host plant genotype and to what extent host genetic mechanisms can modulate plant-microbiota interactions in the face of environmental stresses. Here we surveyed 3,168 root and rhizosphere microbiome samples from 129 accessions of locally adapted Zea, sourced from diverse habitats and grown under control and different stress conditions. We quantified stress treatment and host genotype effects on the microbiome. Plant genotype and source environment were predictive of microbiome abundance. Genome-wide association analysis identified host genetic variants linked to both rhizosphere microbiome abundance and source environment. We identified transposon insertions in a candidate gene linked to both the abundance of a keystone bacterium Massilia in our controlled experiments and total soil nitrogen in the source environment. Isolation and controlled inoculation of Massilia alone can contribute to root development, whole-plant biomass production and adaptation to low nitrogen availability. We conclude that locally adapted maize varieties exert patterns of genetic control on their root and rhizosphere microbiomes that follow variation in their home environments, consistent with a role in tolerance to prevailing stress.

Corynebacterium suedekumii sp. nov and Corynebacterium breve sp. nov., isolated from raw cow's milk.

Four Gram-positive, rod-shaped, none-sporeforming, non-motile isolates were obtained from various raw milk samples taken from the cooling tank on a research farm in Königswinter, Germany. Based on phylogenetic analysis of the 16S rRNA genes and whole genome sequences, all isolates were assigned to the genus Corynebacterium, but were divided in two different groups. All isolates contained C18 : 1 cis 9 and C16 : 0 as predominant fatty acids, as well as traces of C18 : 0. They all contained menaquinones MK-8 (H2) and MK-9 (H2) and produced mycolic acids characteristic for the majority of species belonging to the genus Corynebacterium. 16S rRNA gene sequence similarity values to the closest related type strains Corynebacterium humireducens DSM 45392T and Corynebacterium pilosum DSM 20521T were below 98.7 %, average nucleotide identity values were below 86 % and digital DNA-DNA-hybridization values were below 25 %, indicating that the isolates represent two novel species. The names Corynebacterium suedekumii sp. nov. and Corynebacterium breve sp. nov. are proposed, represented by the type strains LM112T (=DSM 116216T=HAMBI 3782T) and R4T (=DSM 116183T=HAMBI 3785T), respectively.