Dendrogenomic resilience mechanisms of two endangered Mexican spruces

Forest ecosystems worldwide can be affected by extreme climatic events. Trees respond to these occurrences in multidimensional ways, involving various mechanisms, to deal with the effects and restore the forests to their optimal state. Such abilities are known as resilience. Tree ring analysis can be used to evaluate drought resilience. Analysis of dendrophenotypes, together with genetic studies, has become an essential tool for identifying drought resilient genotypes. This study aimed to determine the dendrogenomic resilience mechanisms in the fragmented, isolated, rare endemic Mexican species <i>Picea martinezii</i> and <i>P. mexicana</i> by analysis of annual rings and the associations with SNP markers identified by genotyping by sequencing (GBS). Increment cores and needles for GBS for resilience analysis were collected from <i>P. martinezii</i> trees in three populations, and from <i>P. mexicana</i> trees in two populations. The results show that fundamental dendrogenomic mechanisms were associated with drought resilience in <i>P. martinezii</i> and <i>P. mexicana</i>. PC1 in PCA for five outlier SNPs was linked to annual tracheid width variations in <i>P. martinezii</i> caused by severe drought events in 1962, 1989, 1998 and 2011. These five outlier SNPs were located in genes coding the proteins reticulon-like protein B22, pollen-specific leucine-rich repeat extension, ornithine decarboxylase like, LisH/CRA/RING-U-box domains-containing protein and proline transporter 2-like isoform X1, which are important in the dry stress tolerance metabolism involved in the resilience response in plants. The discovery of genetic markers associated with drought resilience highlights the importance of preserving genetic diversity.