Body traits are important economic factors in the pig industry. Genome‐wide association studies (GWASs) have been widely applied using high‐density genotype data to detect QTL in pigs. The aim of the present study was to detect the genetic variants significantly associated with body traits in crossbred pigs using the Illumina Porcine SNP50 BeadChip and imputed whole‐genome sequence data. A set of seven body traits – body length, body height, chest circumference, cannon bone circumference, leg buttock circumference, back fat thickness and loin muscle depth – were measured. Moderate to high heritabilities were obtained for most traits (from 0.14 to 0.46), and significant genetic and phenotypic correlations among them were observed. GWAS identified 714 significantly associated SNPs located at 39 regions on all autosomes for body traits, and a total of seven functionally related candidate genes: PIK3CD, HOXA, PCGF2, CHST11, COL2A1, BMI1 and OSR2. Functional enrichment analysis revealed that candidate genes were enriched in the estrogen signaling pathway, embryonic skeletal system morphogenesis and embryonic skeletal system development. These results aim to uncover the genetic mechanisms underlying body development and marker‐assisted selection programs focusing on body traits in pigs.

Summary Growth‐related traits are important economic traits in the pig industry that directly influence pork production efficiency. To detect quantitative trait loci and candidate genes affecting growth traits, genome‐wide association studies were performed for backfat thickness (BF) and loin muscle depth (LMD) in 370 Chuying‐black pigs using Illumina PorcineSNP50 BeadChip array. We totally identified 14 BF‐associated SNPs, which included 11 genome‐wide SNPs (P < 1.39E‐06) and 3 chromosome‐wide suggestive SNPs (P < 2.79E‐05) and for LMD, 9 SNPs surpassed the genome‐wide significant threshold (P < 1.39E‐06). These SNPs explained 30.33 and 27.51% phenotypic variance for BF and LMD respectively. Furthermore, 14 and 9 genes nearest to the significant SNPs were selected to be candidate genes, including MAGED1, GPHN, CCSER1, and GUCY2D for BF and PARM1, COL18A1, HSF5, and SCML2 genes for LMD. One significant SNP, which explained 6.07% of phenotypic variance for BF, mapped to a pleiotropic quantitative trait locus with a 494‐kb interval. Together, the SNPs and candidate genes identified in this study will advance our understanding of the complex genetic architecture of BF and LMD traits, and they will also provide important clues for future implementation of a genomic selection program in Chuying‐black pigs.

The Epichloë endophyte- Festuca sinensis association produces alkaloids which can protect the host plant from biotic and abiotic stresses. Alkaloid concentrations depend on the genetic predisposition of grass and endophyte, and are affected by the environment. Endophyte infected F. sinensis of six ecotypes were grown in experimental field and greenhouse for 2 years. Their aboveground plant tissues were collected each season to test for peramine, lolitrem B, and ergot concentrations. The results showed that seasonal changes affected the peramine, lolitrem B and ergot concentrations of Epichloë endophyte- F. sinensis associations; and these three different alkaloids responded differently to seasonal variation. The peramine concentration of six ecotypes of F. sinensis decreased significantly ( p < 0.05) from spring to autumn. The lolitrem B concentration of F. sinensis was higher in autumn than in other seasons. Ergot concentrations of five ecotypes (41, 57, 84, 99, and 141) of F. sinensis peaked in the summer, and lowered in spring and autumn. In addition, the ecotype has insignificant effect ( p > 0.05) on the peramine and lolitrem B concentrations of F. sinensis , but it has a significant impact ( p < 0.05) on the ergot concentrations. We concluded that the seasonal variation and ecotypes can influence the alkaloids produced by the F. sinensis- endophyte associations, but the effects of seasonal conditions on the alkaloid concentrations are more pronounced than ecotypes.

In grasslands, the interactions of foliar fungal diseases and their host plants are largely dependent on grazing by large herbivores. However, the relative importance of direct (i.e. pathogen removal) and indirect effects (i.e. via changes in plant community composition) of long‐term grazing on foliar fungal diseases remains largely unexplored, especially under varied grazing intensities. We conducted a 13‐year experiment to explore the effects of grazing intensity on foliar fungal diseases at both plant population and community levels in a semi‐arid grassland. We quantified the contributions of direct and indirect effects of long‐term grazing on community pathogen load. At the population level, the severity of five rusts and five powdery mildews decreased significantly as grazing intensity increased, whereas two leaf spots increased significantly in severity with increasing grazing intensity. Similarly, at the community level, the pathogen load of rusts and powdery mildews was negatively related to the increase in grazing intensity, whereas the pathogen load of leaf spots was positively related to grazing intensity. Overall, heavy grazing (i.e. 8.7 sheep/ha) significantly increased community pathogen load. Our SEM analysis showed that grazing indirectly increased the pathogen load of leaf spots by increasing disease proneness. Grazing decreased the pathogen load of rusts, but this could not be explained by changes in disease proneness. Overall, the indirect effects via changes in community composition of hosts resulting in the increase in community disease proneness outweighed the direct effect of grazing on community pathogen load. Synthesis and applications. Our study provides the first evidence that long‐term heavy grazing can indirectly increase community pathogen load by increasing the abundances of grazing‐tolerant hosts and decreasing the abundances of grazing‐intolerant hosts. These results provide empirical evidence that the pathogen load of foliar fungal diseases in grasslands can depend on the community context of hosts, which can, in turn, be controlled by large herbivores. We recommend that infectious diseases are considered when predicting the responses of grassland ecosystems to anthropogenic activities. Maintaining light to moderate grazing intensity or establishing an appropriate non‐grazing period could be an effective way to control foliar fungal diseases in grasslands.