Effects of meteorological factors on the defoliation dynamics of the larch caterpillar(Dendrolimus superans Butler)in the Great Xing’an boreal forests

Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors.The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics.The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area,while rainy and humid growing seasons decrease the defoliation area.Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect,followed by the accumulative temperatures of the late instar larval period which had a positive impact,and precipitation during the middle instar larval period which had a negative impact.Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40%of the explained variance.This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.

Matrine inhibits mycelia growth of Botryosphaeria dothidea by affecting membrane permeability

Matrine is a promising botanical antifungal;however, the mechanism underlying the antifungal activity is yet limited. We studied the antifungal activity of matrine and the underlying mechanism in Botryosphaeria dothidea as a model strain. Matrine strongly inhibited mycelial growth of B. dothidea in a dose-dependent manner. Matrine-treated B. dothidea showed morphological and ultrastructural alterations, including shriveled hyphae, plasmolysis, and leakage of cytoplasm related to cell membrane deterioration. In addition, matrine caused significantly high conductivity and absorbance (260 nm) in extracellular matrices and low lipid contents in B. dothidea, indicating increased membrane permeability. Lipid peroxidation showed that matrine resulted in increased malondialdehyde content while enhancing the generation of reactive oxygen species and the activities of superoxide dismutase, catalase, and peroxidase. These results showed that matrine inhibited the mycelial growth of B. dothidea by enhancing cell membrane permeability via membrane lipid peroxidation.

The disease resistance potential of Trichoderma asperellum T-Pa2 isolated from Phellodendron amurense rhizosphere soil

To promote the application of Trichoderma,many countries have collected Trichoderma resources.In the present study,nine isolates were isolated from a rhizosphere soil of Phellodendron amurense and were identified as three species:Trichoderma brevicompactum(one isolate),T.asperellum(two isolates),T.atroviride(six isolates).Dual culture experiments showed that T.asperellum T-Pa2 grew fast and produced the best inhibition rates against six tested pathogens(80.25–91.65%)via competition and mycoparasitism.Populus davidiana×P.alba var.pyramidalis Louche(PdPap poplar)was treated with T-Pa2,which increased the catalase activity,nitrate reductase activity,and content of osmosis molecules significantly(P<0.05).Meanwhile,induction by T-Pa2 increased the resistance of PdPap poplar against Alternaria alternata via modulating the expression of salicylic acid,jasmonic acid,and auxin transduction pathway genes.The results will form the basis for the collection and application of biocontrol agents in forestry.

Identification and genetic characterization of bovine hepacivirus in China:A large scale epidemiological study

Bovine hepacivirus(BovHepV)is a novel virus that was recently discovered in Ghana and Germany in 2015.Until now,this virus has been identified in cattle population worldwide and is classified into subtypes A-G.To fully understand the epidemic situation and genetic characteristic of BovHepV in China,a total of 612 cattle serum samples were collected from 20 farms in seven provinces and municipality in China between 2018 and 2020 and were tested for the presence of BovHepV RNA via semi-nested PCR.The results demonstrated that 49(8.0%)samples were BovHepV RNA-positive.It is noted that BovHepV infection in yak was confirmed for the first time.BovHepV was detected in all the seven provinces,with the positive rate ranging from 3.1%to 13.3%,which indicates a wide geographical distribution pattern of BovHepV in China.Sequencing results revealed that 5'UTR of the 49 field BovHepV strains have a nucleotide similarity of 96.3%-100%between each other and 93.9%-100%with previously reported BovHepV strains.In addition,genetic analysis identified five critical nucleotide sites in 5'UTR to distinguish different subtypes,which was further verified by genomic sequencing and nucleotide similarity analysis.All the 49 Chinese field BovHepV strains were classified into subtype G and this subtype is only determined in cattle in China currently.This study will provide insights for us to better understand the epidemiology and genetic diversity of BovHepV.