Bioremediation of quinclorac injury on tobacco by a rhizosphere bacterium.

The presence of herbicides residues in soil represents a serious problem for agriculture. Quinclorac is a common herbicide applied in rice field, but its residue can cause abnormal growth in successive crop of tobacco in Southern China. Remediation by microorganisms is considered to be an environmentally friendly method to remove such pollutants injury. The aims of this study were to obtain quinclorac remediation isolates and to investigate the possible mechanism(s) of remediation. Six bacterial isolates were obtained from rhizosphere of rice-tobacco rotation fields, and were found to be capable of degrading quinclorac on a mineral salt medium (MSM), with degradation efficiency ranging from 2.1 to 23.7%. Among these isolates, J5 had the highest degradation efficiency, and was identified as Klebsiella variicola based on phylogenetic analyses and a metabolic profile generating by Biolog GEN III system. Bioremediation of quinclorac injury was confirmed using pot assays with tobacco, in which J5 reversed the detrimental effect of quinclorac on leaf area, leaf number, and plant height. The J5 isolate also seemed to promote plant growth, in terms of tobacco seedling growth and seed germination, which were 2.2 times and 1.6 times higher compared to untreated control, respectively. The mechanisms of plant growth promoting (PGP) traits were found to involve nitrogen-fixing, indole-3-acetic acid (IAA) production, and phosphate solubilization ability. In addition, proteomic analysis and relative quantitative PCR revealed an elevated level of 4-hydroxyphenylacetate 3-monooxygenase (HPMO) in quinclorac-treated J5, suggesting that this enzyme may play an important role in quinclorac remediation. This study showed that the J5 isolate could be exploited to not only assist in soil remediation due to quinclorac residue issues but also promote tobacco growth.

First Report of Black Dot Caused by Colletotrichum coccodes on Potato in the Tibet Autonomous Region of China.

Potato black dot causing by Colletotrichum coccodes is a common disease in potato throughout the world, infecting underground stems, tubers, roots and foliage. Potato is becoming the third main food crop produced on ~16,000 ha annually in the Tibet Autonomous Region of China, situated on the world's highest plateau. However, the disease causing by C. coccodes has not been reported in this region. During the disease survey in the Bailang County of Tibet in August, 2020, some potato plants cv. "JiZhang 12" with chlorosis and wilting of foliage were observed. The incidence of affected plants was 20%. Necrotic lesions were also observed on the basal stems of the affected plants. Three affected plants were collected for pathogen isolation and three isolates were obtained for further investigation. The colonies on potato dextrose agar (PDA) were initially white, turning gradually black with age and producing abundant black sclerotia. Conidia were cylindrical, hyaline, aseptate, guttulate, with average size of 13.80 to 18.55×4.94 to 5.35 µm for the three isolates in which 30 conidia each were measured. Such characteristics are similar to C. coccodes (Lees and Hilton, 2003). Mycelial growth rate was 0.69 to 0.74 cm/day at 25 oC over the three isolates. The three isolates were confirmed to be C. coccodes by species-specific PCR using primer set of Cc1NF1/Cc2NR1 producing 350 bp amplicons in the internal transcribed spacer (ITS) region according to Cullen et al. (2002). The Cc1NF1/Cc2NR1 sequences were identical for three isolates, therefore one sequence from isolate BL_JZ_J1 was submitted to the GenBank with accession number OM368349. Additional genes were also sequencing including the actin (ACT), chitin synthase l (CHS1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and another larger ITS region were also amplified from genomic DNA using primers sets ACT512F/ACT783R, CHS-79F/CHS-354R (Carbone and Kohn 1999), GDF1/GDR1 (Templeton et al. 1992) and ITS1/ITS4 (Glass and Donaldson 1995), respectively. Sequences obtained for those four regions were 216 bp, 218bp, 235bp and 576 bp, respectively. Each region in the three isolates were also identical, therefore one sequence for each region was submitted to the GenBank with accession number of OM417059, OM417060, OM417061, and OM349570, respectively, which had 100% similarity with C. coccodes of MN336525 (ACT), KU821274 (CHS1), KU821397 (GAPDH) and KU821175 (ITS), respectively. Phylogenetic analyses based on the concatenated sequences of those four loci showed that the BL_JZ_J1 was close to C. coccodes, a reference isolate of CPOS1 with the accession numbers of GQ856787 (ACT), GQ856723 (CHS1), GQ856744 (GAPDH) and GQ485588 (ITS) (Yang et al. 2009). Pathogenicity was confirmed by inoculating a conidia suspension (100 µl of 105 conidia/ml) on three stems of 6-week-old potato plant cv. 'Favorita' with an artificial wound generated by sterile toothpick for each isolate. An equal volume of sterile water was injected on the wound of three stems as a noninoculated control. Brownish necrotic lesions were observed on all inoculated stems 3 days post-inoculation under natural conditions, whereas control stems remained symptomless. Reisolation of the fungus from all inoculated symptomatic plants confirmed Koch's Postulates. To our knowledge, this is the first report of C. coccodes in potato in Tibet Autonomous Region of China. The finding of black dot in this region has important management implications for the growers since the pathogen can survive for long periods in the field both on potato debris and in soil.

Diagnostic Accuracy of Serum Amyloid A in Acute Appendicitis: A Systematic Review and Meta-Analysis.

Background: Serum amyloid A has been widely reported as a useful biochemical marker in the diagnoses of acute appendicitis. The aim of this study was to appraise the diagnostic accuracy of serum amyloid A in the diagnosis of acute appendicitis. Methods: A systematic search of several databases was conducted. The search time was from the beginning of the databases creation to March 1, 2021, and the languages were restricted to English and Chinese. Clinical studies using serum amyloid A for the diagnosis of acute appendicitis were included. The overall sensitivity and specificity were calculated by using a bivariable mixed effects model. Heterogeneity was tested using I2 statistics. This study has been registered on the International Prospective Register of Systematic Reviews (PROSPERO; no. CRD42021241343). Results: Five studies comprising 668 participants were eligible for inclusion. The overall sensitivity and specificity of serum amyloid A in diagnosing acute appendicitis were 0.87 (95% confidence interval [CI], 0.79-0.92) and 0.74 (95% CI, 0.59-0.85), respectively. The positive and negative likelihood were 3.3 (95% CI, 2.1-5.4) and 0.18 (95% CI, 0.11-0.28), respectively. The area under the summary receiver operating characteristic curves was 0.89 (95% CI, 0.86-0.91). The heterogeneity was significant (I2 = 82%; 95% CI [63%-100%]). Conclusions: Serum amyloid A has good diagnostic accuracy for acute appendicitis. It is expected that serum amyloid A could be helpful in the early clinical diagnosis of acute appendicitis.