The first two whole mitochondrial genomes for the genus Dactylis species: assembly and comparative genomics analysis.

BACKGROUND: Orchardgrass (Dactylis glomerata L.), a perennial forage, has the advantages of rich leaves, high yield, and good quality and is one of the most significant forage for grassland animal husbandry and ecological management in southwest China. Mitochondrial (mt) genome is one of the major genetic systems in plants. Studying the mt genome of the genus Dactylis could provide more genetic information in addition to the nuclear genome project of the genus. RESULTS: In this study, we sequenced and assembled two mitochondrial genomes of Dactylis species of D. glomerata (597, 281 bp) and D. aschersoniana (613, 769 bp), based on a combination of PacBio and Illumina. The gene content in the mitochondrial genome of D. aschersoniana is almost identical to the mitochondrial genome of D. glomerata, which contains 22-23 protein-coding genes (PCGs), 8 ribosomal RNAs (rRNAs) and 30 transfer RNAs (tRNAs), while D. glomerata lacks the gene encoding the Ribosomal protein (rps1) and D. aschersoniana contains one pseudo gene (atp8). Twenty-three introns were found among eight of the 30 protein-coding genes, and introns of three genes (nad 1, nad2, and nad5) were trans-spliced in Dactylis aschersoniana. Further, our mitochondrial genome characteristics investigation of the genus Dactylis included codon usage, sequences repeats, RNA editing and selective pressure. The results showed that a large number of short repetitive sequences existed in the mitochondrial genome of D. aschersoniana, the size variation of two mitochondrial genomes is due largely to the presence of a large number of short repetitive sequences. We also identified 52-53 large fragments that were transferred from the chloroplast genome to the mitochondrial genome, and found that the similarity was more than 70%. ML and BI methods used in phylogenetic analysis revealed that the evolutionary status of the genus Dactylis. CONCLUSIONS: Thus, this study reveals the significant rearrangements in the mt genomes of Pooideae species. The sequenced Dactylis mt genome can provide more genetic information and improve our evolutionary understanding of the mt genomes of gramineous plants.

Combined Genome-Wide Association Study and Transcriptome Analysis Reveal Candidate Genes for Resistance to Rust (Puccinia graminis) in Dactylis glomerata.

Rust disease is a common plant disease that can cause wilting, slow growth of plant leaves, and even affect the growth and development of plants. Orchardgrass (Dactylis glomerata L.) is native to temperate regions of Europe, which has been introduced as a superior forage grass in temperate regions worldwide. Orchardgrass has rich genetic diversity and is widely distributed in the world, which may contain rust resistance genes not found in other crops. Therefore, we collected a total of 333 orchardgrass accessions from different regions around the world. Through a genome-wide association study (GWAS) analysis conducted in four different environments, 91 genes that overlap or are adjacent to significant single nucleotide polymorphisms (SNPs) were identified as potential rust disease resistance genes. Combining transcriptome data from susceptible (PI292589) and resistant (PI251814) accessions, the GWAS candidate gene DG5C04160.1 encoding glutathione S-transferase (GST) was found to be important for orchardgrass rust (Puccinia graminis) resistance. Interestingly, by comparing the number of GST gene family members in seven species, it was found that orchardgrass has the most GST gene family members, containing 119 GST genes. Among them, 23 GST genes showed significant differential expression after inoculation with the rust pathogen in resistant and susceptible accessions; 82% of the genes still showed significantly increased expression 14 days after inoculation in resistant accessions, while the expression level significantly decreased in susceptible accessions. These results indicate that GST genes play an important role in orchardgrass resistance to rust (P. graminis) stress by encoding GST to reduce its oxidative stress response.

Yield of white clover and orchard grass cultivated in mining passives adding black earth and compost as a substrate.

Mining environmental liabilities generate environmental pollution. The objective of the present study was to determine the yield of white clover (Trifolium repens) and orchard grass (Dactylis glomerata) cultivated in mining environmental passives adding black earth and compost as a substrate in the Buenaventura Julcani Huancavelica Company. The treatments were the combinations: 4: 3.1: 3.1: 3:1.1 kg of RP: RP, TN: RP, C: RP, TN, C respectively. They were distributed in four treatments with twelve experimental units for each species of leguminous and gramineous grass, we worked according to the completely randomized design (DCA) with a 2 x 4 factorial arrangement, the experimental unit being a treatment with twelve repetitions. The variables evaluated were: germination percentage (TG) and stem survival percentage (TST). For the statistical analysis, the SPSS software was used.

Effect of harvesting strategy of second-cut orchardgrass silage on feed intake, digestion, and milk production in dairy cows.

We investigated the effects of regrowth interval and first-cut timing on the dietary characteristics of second-cut orchardgrass silage and feed intake and milk production in dairy cows fed second-cut orchardgrass silage. The second-cut grasses were harvested 7w after the first-cut at the early stage (E7w) or at the heading stage (H7w), or harvested 6w after the first-cut at the early stage (E6w) from orchardgrass sward, and then ensiled. We evaluated the effect of regrowth interval by comparing E7w and E6w, and the effect of first-cut timing by comparing E7w and H7w. Six multiparous Holstein cows were used in a replicated 3 × 3 Latin square design, with three dietary treatments: diets containing E7w, E6w, or H7w silage at 30% dietary dry matter. We observed that feeding E6w silage instead of E7w silage increased fiber digestibility, dry matter intake, and milk production; however, the first-cut timing (E7w vs. H7w) did not affect nutrient content and digestibility, feed intake, or lactation performance. These results show that harvesting at short regrowth intervals for second-cut orchardgrass can be an effective strategy for improving feed utilization and milk yield; however, the first-cut timing for second-cut orchardgrass has little impact.