Contribution of pathogenic fungi to N2O emissions increases temporally in intensively managed strawberry cropping soil.

Intensively managed agriculture land is a significant contributor to nitrous oxide (N2O) emissions, which adds to global warming and the depletion of the ozone layer. Recent studies have suggested that fungal dominant N2O production may be promoted by pathogenic fungi under high nitrogen fertilization and continuous cropping. Here, we measured the contribution of fungal communities to N2O production under intensively managed strawberry fields of three continuous cropping years (1, 5, and 10 years) and compared this adjacent bare soil. Higher N2O emission was observed from the 10-year field, of which fungi and prokaryotes accounted for 79.7% and 21.3%, respectively. Fungal population density in the 10-year field soil (4.25 × 105 colony forming units per g (CFU/g) of air-dried soil) was greater than the other cropping years. Illumina MiSeq sequencing of the nirK gene showed that long-term continuous cropping decreased the diversity of the fungal denitrifier community, but increased the abundance of Fusarium oxysporum. Additionally, F. oxysporum produced large amounts of N2O in culture and in sterile 10-year field soil. A systemic infection displayed by bioassay strawberry plants after inoculation demonstrated that F. oxysporum was a pathogenic fungus. Together, results suggest that long-term intensively managed monocropping significantly influenced the denitrifying fungal community and increased their biomass, which increased fungal contribution to N2O emissions and specifically by pathogenic fungi. KEY POINTS: • Distinguishing the role of fungi in long-term continuous cropping field. • Identifying the abundant fungal species with denitrifying ability.

The complete mitochondrial genome of Hemerobius japonicus (Neuroptera: Hemerobiidae).

The complete mitochondrial genome of Hemerobius japonicus Nakahara, 1915 was sequenced in this study. The complete mitochondrial genome is a typical double-stranded circular molecule of 18,585 bp (GenBank accession number: MN852445), containing 37 typical animal mitochondrial gene and an A + T-rich region. The gene order is identical to that of the putative ancestral arrangement of insects and other lacewings. 13 protein-coding genes (PCGs) possessed common triplet initiation codons ATN except ND1 possessed TTG and mostly terminated with TAN codons except for ND5 and ND4 with a single T residue adjacent to a downstream tRNA gene. All of the 22 tRNAs, ranging from 63 to 72 bp, can be folded into classic clover-leaf secondary structure except for tRNASer(AGN) , in which the dihydrouridine (DHU) arm did not form a stable stem-loop structure. The control region is 1416 bp long with an A + T content of 90.3%. In the sampled families of Neuroptera, each family showed a monophyletic cluster and Polystoechotidae + Rapismatidae, Osmylidae + the remaining families, Hemerobiidae + (Chrysopidae + (Polystoechotidae + Rapismatidae)) are recovered in phylogenetic analyses with high supports.

The complete mitochondrial genome of Hemerobius spodipennis (Neuroptera: Hemerobiidae).

The complete mitochondrial genome of Hemerobius spodipennis Yang, 1987 was sequenced in this study. The complete mitochondrial genome is a typical double-stranded circular molecule of 16,343 bp (GenBank accession number: MT268963) comprising of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and a control region. The gene order is identical to that of the putative ancestral arrangement of insects and other lacewings. All protein-coding genes initiate with ATN, except COI use CGA as start codons and terminate with TAG or TAA, expect ND5 and ND4 use TA- or a single T-- residue as the stop codon. All tRNAs, ranging from 63 to 72 bp, can be folded into typical clover-leaf secondary structure except for tRNASer(AGN) , in which the dihydrouridine (DHU) arm did not form a stable stem-loop structure. The control region is 1433 bp long with an A + T content of 91.4%. In the sampled families of Neuroptera, each family showed a monophyletic cluster and Polystoechotidae + Rapismatidae, Hemerobiidae + (Chrysopidae + (Polystoechotidae + Rapismatidae)), are recovered in phylogenetic analyses with high supports.

Contrasting beneficial and pathogenic microbial communities across consecutive cropping fields of greenhouse strawberry.

Soil weakness across consecutive cropping fields can be partially explained by the changes in microbial community diversity and structure. Succession patterns and co-occurrence mechanisms of bacteria and fungi, especially beneficial or pathogenic memberships in continuous cropping strawberry fields and their response to edaphic factors remained unclear. In this study, Illumina sequencing of bacterial 16S ribosomal RNA and fungal internal transcribed spacer genes was applied in three time-course (1, 5, and 10 years) fields across spring and winter. Results showed that the richness and diversity of bacterial and fungal communities increased significantly (p < 0.05) in 1-year field and decreased afterwards across two seasons. Network analysis revealed beneficial bacterial and fungal genus (Bacillus and Trichoderma) dominated under 1-year field whereas Fusarium accumulated under 10-year field at either season. Moreover, Trichoderma harzianum and Bacillus subtilis that have been reported to effectively control Fusarium wilt in strawberries accumulated significantly under 1-year field. Canonical correspondence analysis showed that beneficial bacterial Rhodospirillales and Rhizobiales and fungal Glomerales accumulated in 1-year field and their distributions were significantly affected by soil pH, microbial biomass C (MBC), and moisture. On the contrary, fungal pathogenic species Fusarium oxysporum strongly increased under 10-year field at the winter sample and the abundance was positively (p < 0.01) correlated with soil moisture. Our study suggested that the potential of microcosm under 1-year field stimulates the whole microbial diversity and favors different beneficial taxa across two seasons. Soil pH, moisture, and MBC were the most important edaphic factors leading to contrasting beneficial and pathogenic memberships across consecutive strawberry cropping fields.