ABSTRACT
Pennycress (Thlaspi arvense L.), an annual herb of the mustard family Brassicacae, is native to Eurasia and now widely distributed throughout temperate North America. This species is currently being developed as a medicinal herb used to treat nephritis in China and an oilseed crop for biofuel production (Roque et al.2012). In November 2020, stunt and wilt symptoms were observed on above ground parts and swollen club-shaped galls were observed on the roots of T. arvense in most of the Chinese cabbage growing area in Kangding (30°03'"N,102°02'"E), Sichuan Province of China. The average disease incidence of swollen roots on T. arvense was 91.2% ( n=80). To identify the causal agent of this disease, the swollen roots of T. arvense were collected, crushed and observed under microscope (Fei et al.2017). Abundant resting spores were found in the root galls, which were spherical and 2.0 to 3.1 µm in diameter with an average length of 2.7 nm (n=100). The healthy roots and the root galls of T. arvense plants were further evaluated by PCR with P. brassicae-specific primers TC2F/TC2R (Cao et al. 2007). The results showed that a DNA fragment with an estimated size of 520 bp, as expected for that of P. brassicae, was consistently amplified in diseased roots, No PCR amplification occurred in the healthy roots with the TC2F/TC2R primers. Blast analysis of the 520 bp segment (GenBankMZ040496) showed the highest identity with the sequence of small subunit ribosomal RNA gene of P. brassicae (GenBankMH762161, 97.7%, E value=0). These results confirmed that the pathogen in the galled roots of T. arvense was P. brassicae. The pathogenicity of isolated P. brassicae was tested on both T. arvense and Chinese cabbage (B. campestris ssp. pekinensis). Resting spores were isolated from the diseased roots (Castlkbury et al. 1994) of T. arvense and suspended in Hoagland's solution to the final concentration of 1 × 107 spores per milliliter. Fifteen plastic pots (10 cm bottom diameter, 16 cm upper diameter, 13 cm high) were filled with soil (1 kg per pot) that was sterilized twice with high-temperature (121â), high pressure (19 PSI) for 1.5 hours with a time interval of 2 days between. Inoculated pots received 100 mL spore suspension each. Fifteen control pots with sterilized field soil were treated with 100 mL Hoagland's solution each. Seeds of T. arvense and B. campestris were pre-germinated at 20°C on moist filter paper for 7 days and transplanted into the pots, five seedlings each and five pots per treatment. The pots were maintained in a greenhouse with 16 hours photoperiod at 24°C/16°C day/night temperature. After 7 weeks, plants in each pot were uprooted and the roots cleaned in running water and inspected for clubroot symptoms. Plants of T. arvense and Chinese cabbage in pots inoculated with resting spores showed clubroot symptoms while no disease symptoms were observed on any control plants. The disease incidence rate was 95.4% on T. arvense and 81.2% on B. campestris. Therefore, it was confirmed that P. brassicae could cause clubroot disease on T. arvense. To our knowledge, this is the first published report of clubroot disease on T. arvense in China. This finding is helpful for the management of clubroot on herbs and plants of biological origin in the cruciferous family.
ABSTRACT
We report the complete mitochondrial genome (mtDNA) of Pareas formosensis (Squamata: Colubridae). This circular mtDNA is 17,703 bp in size and consists of 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and 2 non-coding sequence (D-loop). The total of mtDNA was composition of 57.26% A + T and 42.74% G + C (T: 25.21%, C: 28.84%, A: 32.05%, G: 13.90%). The phylogenetic analysis revealed that P. formosensis formed a clade with other species of Pareas. This mtDNA sequence of P. formosensis provides useful data for studying the population genetics and phylogeography of Colubridae.
ABSTRACT
Brown spot disease caused by Colletotrichum species was found on leaves of mulberry (Morus alba L.) in Dujiangyan, Sichuan Province, China. Fungal isolates from leaf lesions were identified as six Colletotrichum species based on morphological characteristics and DNA analysis of the combined sequences ITS, GAPDH, ACT, CHS-1, TUB2, and GS. These included Colletotrichum fioriniae, C. fructicola, C. cliviae, C. karstii, C. kahawae subsp. ciggaro, and C. brevisporum. Results showed that the most important causal agent of mulberry anthracnose was C. fioriniae, causing typical brown necrotic spots or streaks, followed by C. brevisporum, C. karstii, and C. kahawae subsp. ciggaro, whereas the two other species (C. fructicola and C. cliviae) showed no pathogenicity to mulberry. This study is the first report of these species associated with mulberry in China.
Subject(s)
Colletotrichum , Morus , Phylogeny , Virulence , China , Colletotrichum/pathogenicity , DNA, Fungal/genetics , Morus/microbiology , Plant Diseases/microbiology , Plant Leaves/microbiology , Species SpecificityABSTRACT
Clubroot, caused by the soil-borne obligate pathogen Plasmodiophora brassicae, is one of the most severe disease in cruciferous crops. Previous studies showed that when oilseed rape was planted after soybean (namely soybean-oilseed rotation), the incidence and severity of clubroot of oilseed rape could be significantly reduced, compared with that with oilseed rape-oilseed rape conti-nuous cropping. Therefore, the soybean-oilseed rape rotation is a good way to suppress clubroot of oilseed rape. In this study, we compared the rhizosphere microbiome of soybean and oilseed rape rhizosphere soil collected from the field by 16S rRNA (for identification of prokaryotes) and the internal transcribed spacer (ITS) (for identification of fungi) sequencing. The results showed that both soybean and oilseed rape rhizosphere soils had Proteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, Ascomycota, Zygomycota, Basidiomycota and Chytridiomycota. Many microbial genera (e.g., Flavobacterium, Sphingomonas, Bacillus, Streptomyces, Pseudomonas, Trichoderma and Coniothyrium) with activities of biological control and plant growth promotion were more abundant in soybean rhizosphere soil than in the oilseed rape rhizosphere soil. The abundance of plant pathogenic bacteria and fungi was higher in the oilseed rape rhizosphere soil than in the soybean rhizosphere soil. Moreover, the soybean rhizosphere soil was enriched with Rhizobium, Bradyrhizobium (both for nitrogen fixation), and arbuscular mycorrhizal fungus (Glomus). These results indicated that soybean rhizosphere soil could promote the growth and proliferation of beneficial microorga-nisms, but inhibit that of plant pathogens. Our results provide evidence for explanation of the effectiveness of soybean-oilseed rape rotation to control clubroot of oilseed rape and provide potential bio-control resources for clubroot prevention.
Subject(s)
Microbiota , Rhizosphere , Soil Microbiology , Brassica rapa/growth & development , Brassica rapa/microbiology , High-Throughput Nucleotide Sequencing , RNA, Ribosomal, 16S , Glycine max/growth & development , Glycine max/microbiologyABSTRACT
BACKGROUND: The objective of this study was to investigate how treatment strategies in the same treatment affected the canine's initial displacement and the stress in periodontal ligament using three-dimensional finite element analysis. And to find out the way to design an effective treatment plan. METHODS: Based on computed tomography images of the teeth and their supporting tissues, solid models were used to build finite element models. Three treatment plans of three different transparent tooth correction therapies finite element-analyses were operated. RESULTS: The canine's initial displacement and stresses' distribution in periodontal ligament were obtained. CONCLUSIONS: For rotation movement, the canine should rotate along tooth long axis, and not combine with other kinds of tooth movement as possible. For translation movement, the combination of translation and inclination movement is helpful for the treatment.
