Channel: ETIOLOGY http://zwblxb.magtech.com.cn EN-US http://zwblxb.magtech.com.cn/EN/current.shtml http://zwblxb.magtech.com.cn 5 Acer truncatum Bunge in Guiyang City, Guizhou Province, we collected diseased samara for pathogen isolation. YB26, a representative fungal strain causing the disease through pathogenicity test, was identified as Alternaria alternata based on combined results of morphological characteristics and multigene (rDNA-ITS, Alt a1 and GAPDH) phylogenetic analysis. Then the biological characteristics of A. alternata strain YB26 were determined by testing the mycelial growth rate under different carbon and nitrogen sources, temperatures, pH values, media and light conditions. The results showed that the suitable conditions for vegetative growth of YB26 were mannitol as carbon source, beef extract as nitrogen source, Sabouraud glucose agar (SDA) as culture medium, temperature of 28 ℃, pH value of 7, and incubation under darkness. Furthermore, the inhibitory effects of 7 fungicides against strain YB26 were tested, among which 25% pyrisoxazole had the best antifungal activity, with the EC₅₀ value of 0.8323 mg·L^-1. This is the first report of samara brown spot on A. truncatum caused by A. alternata. The results provide a basis for the diagnosis and control of the disease on A. truncatum.]]> Ligustrum japonicum leaf spot occurs universally in Wenhuilu campus of Yangzhou university, Yangzhou, Jiangsu, China every spring. The aim of this study was to identify the pathogen species, determine the biological characteristics, and screen out effective pesticides for the prevention and control of the disease.The multiple assays were conducted for the pathogen identification including tissue separation and single-spore purification, pathogenicity test both in vitro and vivo to fulfill Koch’s postulates, and morphological and phylogenetic analysis based on a combined ITS, GAPDH, RPB2 and TEF1 sequence dataset, the biological characterization,and the sensitivity test to the five fungicides. We obtained the purified fungal culture which was further identified as Alternaria alternata, a new pathogen causing leaf spot on L. japonicum. The effect of various carbon and nitrogen sources for growing of the representative isolate was investigated and A. alternata isolate was suitable for growing on the optimized medium supplied with sucrose, fructose, and potassium nitrate at 25 ℃, pH 9.0. In addition, 5 fungicides were assessed on the inhibitory effect against mycelial growth of A. alternata isolate in which azoxystrobin displayed the strongest inhibitory activity with EC₅₀ value of 0.080 6 μg·mL^-1, followed byprochloraz, pyraclostrobin and tebuconazole with EC₅₀ values of 2.272 2 μg·mL^-1, 3.934 9 μg·mL^-1 and 6.400 0 μg·mL^-1, respectively, while difenoconazole exhibited the least sensitivity at EC₅₀ value of 15.486 0 μg·mL^-1. These results indicated that these fungicides could be used for the prevention and control of L. japonicum leaf spot disease.]]> Achyranthes bidentata showing typical symptoms of Fusarium wilt were collected from Jiaozuo, Henan Province, China. Tissue separation method was used to obtain potential pathogenic fungal isolates, and the pathogenicity of these isolates was determined by root-dipping inoculation method. Fusarium proliferatum was identified as the causal agent of the disease based on morphological characteristics, ITS sequence and polygenic analysis (EF1-α, Tub, RPB2 and PRO1/2). F. proliferatum isolates showed maximum radial growth at 28 ℃ and pH 7.0 on oatmeal agar medium under dark conditions. The pathogen could utilize multiple carbon and nitrogen sources, with the best carbon and nitrogen sources of sucrose and peptone, respectively. To our knowledge, this is the first report of F. proliferatum causing Fusarium wilt on A. bidentata. The results provide a scientific basis for diagnosis and control of Fusarium wilt of A. bidentata. Toxicity test of the six fungicides on F. proliferatum showed that these fungicides had certain inhibitory effects on the pathogen, and tebuconazole and fludioxonil exhibited relative higher inhibitory effects, with EC₅₀ values of 3.03 and 2.36 mg·L^-1, respectively.]]> Broussonetia papyifera samples suspected to be infected by Begomovirus, with yellow mosaic leaves, were collected from Lianping county, Heyuan city, Guangdong province. Total DNA was extracted from suspected samples individually, and was used as template for PCR detection with degenerate Begomovirus pri-mers AV₄₉₄/CoPR. The PCR detection result showed that three suspected samples were infected by Begomovirus. The full genome sequence of virus isolated from Broussonetia papyifera in Guangdong (GS-2021) was obtained by RCA amplification, followed by enzyme digestion, cloning and sequencing. GS-2021 was a bipartite virus, including DNA-A and DNA-B components. The full sequence of DNA-A (GS-2021-A) was 2 777 nt in size, and encoded seven ORFs. The full sequence of DNA-B (GS-2021-B) was 2 742 nt in size, and encoded two ORFs. GS-2021 shared the higher similarity with all isolates of clerodendrum golden mosaic China virus (ClGMCNV). GS-2021-A shared a 93.0%-93.9% identity with DNA-A of all isolates of ClGMCNV, and the highest identity (93.9%) is with the Fujian Fz7 isolate (GenBank accession number: FJ011668). GS-2021-B shared an 86.3%-89.6% identity with DNA-B of all isolates of ClGMCNV, and the highest identify (89.6%) is with the Fujian Fz7 isolate (GenBank accession number: FJ011669). GS-2021 was closely related to five isolates of ClGMCNV from Fujian, Zhejiang, Jiangsu and the United States, which belonged to the same clade. In addition, GS-2021 clustered with Fz7 isolate from Fujian in a small clade, and had the closest relationship with it. Recombination analysis showed that there was no obvious gene recombination event in GS-2021. Based on the latest demarcation threshold for Begomovirus, GS-2021 was a new strain of ClGMCNV. In this study, Begomovirus was detected on Broussonetia papyifera for the first time. The full viral genome sequence of this virus was obtained and identified as a new strain of ClGMCNV. This result shows that Broussonetia papyifera is a newly discovered natural host for Begomovirus.]]> Citrullus lanatus is an important horticultural plant. Viral diseases on C. lanatus have become more and more serious in recent years. In order to identify the viruses that infect watermelons, the small RNA deep sequencing was used to analyze samples with mosaic and shrinking symptoms from Taigu District, Shanxi Province. RT-PCR and bioinformatics methods were used to analyze the pathogens. The results showed that the watermelon samples exhibiting mosaic and shrinking symptoms were infected by five viruses including cucurbit aphid-borne yellows virus (CABYV), cucurbit melo cryptic virus (CmCV), watermelon virus A (WVA), watermelon crinkle leaf-associated virus 2 (WCLaV2) and cucumber green mottle mosaic virus (CGMMV). The coat protein (CP) sequences of five viruses were amplified by RT-PCR, and further analyzed by sequence identity analysis and phylogenetic analysis. It was found that the nucleotide sequence of CABYV-SXJZ (GenBank No : OP957280) obtained in this study had the highest identity with that of CABYV-Inner Mongolia (GenBank No : EU262627), reaching 100%. The nucleotide sequence of watermelon WVA isolate WVA-SXJZ (GenBank No : OP957281) has the highest identity with that of watermelon WVA isolate WVA-Huizhou (GenBank No : MK292710) and watermelon WVA isolate WVA-KF15 (GenBank No : KY363796), which are also from China, reaching 93.6% and 99.9%, respectively. The nucleotide sequence of WCLaV2 isolate WCLaV2-SXJZ (GenBank No : OP957282) has the highest identity with that of WCLaV2 Brazilian watermelon isolate Ju-01 (GenBank No : LC636075), reaching 99.6%. The nucleotide sequence of CmCV isolate CmCV-SXJZ (GenBank No : OP957283) obtained from watermelon for the first time in this study has 99.9% identity to that of Chinese melon isolate CmCV-HLJ (GenBank No : MH479773). The nucleotide sequence of CGMMV isolate CGMMV-SXJZ (GenBank No : OP957284) obtained in this study has the highest identity with CGMMV isolate GDLZ (GenBank No : MK933286), CG038 (GenBank No : MH271443), CGMMV-pXT1 (GenBank No : KY753929), eWT (GenBank No : KY753928), C284R (GenBank No : KY753927), CGMMV-XG (GenBank No : KP868654), JD2 (GenBank No : KM873785) and Anhui (GenBank No: KT236095), reaching 99.8%.]]>