Genetic Diversity and Genome-Wide Association Study of Seed Aspect Ratio Using a High-Density SNP Array in Peanut (Arachis hypogaea L.).

Peanut (Arachis hypogaea L.) is one of the important oil crops of the world. In this study, we aimed to evaluate the genetic diversity of 384 peanut germplasms including 100 Korean germplasms and 284 core collections from the United States Department of Agriculture (USDA) using an Axiom_Arachis array with 58K single-nucleotide polymorphisms (SNPs). We evaluated the evolutionary relationships among 384 peanut germplasms using a genome-wide association study (GWAS) of seed aspect ratio data processed by ImageJ software. In total, 14,030 filtered polymorphic SNPs were identified from the peanut 58K SNP array. We identified five SNPs with significant associations to seed aspect ratio on chromosomes Aradu.A09, Aradu.A10, Araip.B08, and Araip.B09. AX-177640219 on chromosome Araip.B08 was the most significantly associated marker in GAPIT and Regularization method. Phosphoenolpyruvate carboxylase (PEPC) was found among the eleven genes within a linkage disequilibrium (LD) of the significant SNPs on Araip.B08 and could have a strong causal effect in determining seed aspect ratio. The results of the present study provide information and methods that are useful for further genetic and genomic studies as well as molecular breeding programs in peanuts.

Inference on Paleoclimate Change Using Microbial Habitat Preference in Arctic Holocene Sediments.

The present study combines data of microbial assemblages with high-resolution paleoceanographic records from Core GC1 recovered in the Chukchi Sea. For the first time, we have demonstrated that microbial habitat preferences are closely linked to Holocene paleoclimate records, and found geological, geochemical, and microbiological evidence for the inference of the sulphate-methane transition zone (SMTZ) in the Chukchi Sea. In Core GC1, the layer of maximum crenarchaeol concentration was localized surrounding the SMTZ. The vertically distributed predominant populations of Gammaproteobacteria and Marine Group II Euryarchaeota (MG-II) were consistent with patterns of the known global SMTZs. MG-II was the most prominent archaeal group, even within the layer of elevated concentrations of crenarchaeol, an archaeal lipid biomarker most commonly used for Marine Group I Thaumarchaeota (MG-I). The distribution of MG-I and MG-II in Core GC1, as opposed to the potential contribution of MG-I to the marine tetraether lipid pool, suggests that the application of glycerol dibiphytanyl glycerol tetraethers (GDGT)-based proxies needs to be carefully considered in the subsurface sediments owing to the many unknowns of crenarchaeol. In conclusion, microbiological profiles integrated with geological records seem to be useful for tracking microbial habitat preference, which reflect climate-triggered changes from the paleodepositional environment.