Mulberry (Morus alba L.) is an economically important crop grown widely throughout Asia. Various virus-like symptoms including mosaics, vein banding, and chlorotic ringspots have been observed and reported on mulberry trees in China and Japan for decades. However, the etiology of mulberry viral diseases is generally understudied, although two mulberry-infecting viruses, Mulberry latent virus (genus Carlavirus) (2) and Mulberry ringspot virus (genus Nepovirus) (3), have been partially characterized. In a recent (2010 to 2011) field survey in Guangxi Province, China, supported by the local government, the incidence of virus-like diseases of mulberry ranged between 40 and 80%. To identify the viruses infecting mulberry, deep sequencing of small RNAs (4) was conducted using an Illumina Genome Analyzer. Small RNAs were isolated from five samples of mulberry leaves showing various virus-like symptoms and sequenced. Among the contigs assembled, a 445-bp contig (GenBank Accession No. JX268597) was found to share 76.6% nucleotide identity and 83.0% amino acid identity to Groundnut bud necrosis virus (genus Tospovirus, family Bunyaviridae; Accession Nos. U42555 and AAC55521). To obtain a longer cDNA fragment of this virus, a reverse transcription (RT)-PCR was done with primers MV-N-F (5′-AAGCCATCAATGTGCCTCCGGA-3′) and MV-N-R (5′-AACACCATGTCTACCGTCCGTC-3′) that align to the S-RNA sequence encompassing the nucleocapsid (N) gene and a portion of the intergenic region (IGR) of the Tospovirus. PCR products of about 1,000 bp were successfully amplified from the total RNA of the three mulberry samples (sl-1, xcsy-1, and xcsy-4) showing vein banding symptoms, but not from asymptomatic mulberry (jk-1). These PCR products were cloned and sequenced. The lengths of the amplicons were 1,027 bp (isolate sl-1, JX173786), 987 bp (isolate xcsy-1, JX173787), and 979 bp (isolate xcsy-4, JX173788) and the partial IGRs of the sl-1, xcsy-1, and xcsy-4 isolates were 187 bp, 147 bp, and 139 bp, respectively. The coding regions for the N protein were 831 bp and the deduced proteins of 277 amino acid residues were 100% identical for all three isolates. Since the N protein of this virus shared up to only 74.4% identity to other tospoviruses (74.4% to Capsicum chlorosis virus, ABB83818; and 71.5% to Watermelon bud necrosis virus, ABY79095), it may represent a new member of the Tospovirus genus, temporarily named Mulberry vein banding virus (MuVBV), according to the species demarcation criteria for the Bunyaviridae (1). To the best of our knowledge, this is the first report of a Tospovirus infecting M. alba. In an RT-PCR screening of 48 randomly selected mulberry samples suspected to be virus-infected, 32 were MuVBV-positive. Giving the high incidence and the high yield loss associated with Tospovirus and the presence of thrips, suspected vectors for the virus, MuVBV may represent a substantial threat to the silkworm industry in China. References: (1) M. Q. K. Andrew et al. Virus Taxonomy: 9th Report of the ICTV. Elsevier Academic Press, San Diego, 2012. (2) T. Tsuchizaki. Annu. Phytopath. Soc. Japan 42:304, 1976. (3) T. Tsuchizaki et al. Annu. Phytopath. Soc. Japan 37:266, 1971. (4) Q. Wu et al. PNAS. 107:1606, 2010.

The consensus problem of nonlinear multi-agent systems with nonuniform time-varying connection topologies via two novel distributed hybrid control protocols is discussed. By using the degrees of freedom brought by coupling weights, impulsive control with impulse time windows integrates intermittent control and impulsive control into a unified control framework and is more suitable for the situations where only the time intervals in which impulses occur are known but the exact instants of impulses cannot be identified. Compared with intermittent control, the intermittent impulsive control (IIC) reduces the amount of data transmission and improves the security of the system. The introduction of the rest windows makes the IIC break the limit of the upper bound of impulsive intervals of general impulsive control, and the system is easier to maintain according to plan. Control-time-dependent Lyapunov function based methods are developed to overcome the difficulty of stability analysis of the error systems caused by continuous switching of multiple dynamic subsystems. Two consensus criteria are presented and the corresponding controller design schemes are proposed. The results can uniformly deal with the positive and negative effects of impulses, and do not require at least one subsystem of the error system to be stable. Three examples are given to demonstrate the effectiveness of the derived theoretical results.

Guava (Psidium guajava) cv. Watermelon Bar was introduced into Guangxi province of China in 2015, and subsequently planted on more than 5,000 ha in Yulin city alone. Black spot disease on fruit was observed between June and October 2015. Once few diseased fruits were found on a guava tree, more than 30% fruits were found to be infected in a several days later. In the field, the fruits from more than 90% guava trees were infected by the disease. Spots containing pycnidia were dark brown to black, sunken, and 3 to 22 mm in diameter. Nine diseased guava fruits were collected from three trees in West Bank village (22.695387N, 110.112299E), Yuzhou District, Yulin City of Guangxi in China. Tissues from the margin between healthy and diseased portions of the fruit were excised and surface sterilized by immersing in 75% ethanol for 3 min, washed with sterile water three times, cut into 0.2 to 0.3 cm2 pieces, and placed on potato dextrose agar (PDA). After 3 days of incubation at 27℃, greyish-green fungal colonies developed. Hyphal tips were subcultured on PDA and OA (oat agar), incubated at 27℃ in a 12 h light/12 h dark cycle for 9 to 10 days until small black pycnidia appear under the mycelia, after which conidia were observed from pycnidia under the optical microscope. Pycnidia were black, granular and in clusters. Conidia were hyaline, unicellular, obovate, 7.47 to 14.49 μm × 5.01 to 9.63 μm, with mucoid sheath and apical mucilaginous appendage. After incubating for 20 days, black, granular and agglomerate perithecia under the mycelia were observed. Pressed the perithecia slightly on a slide, asci were squeezed out which were 8-spored, subcylindrical to clavate, 56.74 to 88.27 μm × 7.88 to 12.16 μm. Ascospores were hyaline, unicellular, multiguttulate, fusiform, wider in the middle, and 10.50 to 16.19 μm × 3.64 to 5.86 μm. Spermatia were hyaline, bacilliform with swollen ends, 3.15 to 8.99 μm × 1.02 to 1.88 μm. The single-spore isolate, YLWB01, was selected as one of 24 representative isolates, for molecular identification. DNA of the isolate YLWB01 was extracted, and the internal transcribed spacer (ITS) region, and the actin (ACT) and translation elongation factor 1 alpha (TEF) gene fragments were amplified using primers ITS1/ITS4 (White et al. 1990), ACT512F/ACT783R and ER728F/EF986R (Carbone et al. 1999), respectively. BLAST analysis in the GenBank database shown that obtained sequence of ITS (MN958712), ACT (MN958710) and TEF (MN958711) had 100% identify to Phyllosticta capitalensis (GenBank accession: AM403717, JN791558 and FJ538377, respectively). Phylogenetic analysis by neighbor-joining using MEGA 6.0 (Tamura. et al. 2013; Guarnaccia. et al. 2017) results shown that ITS, ACT and TEF sequences clustered together with P. capitalensis (strain CPC18848) in the phylogenetic tree. Based on these morphological characteristics and sequence analysis (Wikee et al. 2013), the fungus was identified as P. capitalensis, cause of guava black spot disease (Arafat 2018). Pathogenicity of YLWB01 single-spore isolate was demonstrated on fruits surface sterilized by 75% ethanol in the laboratory, six symptomless mature guava fruits were stab wounded, three stabs per fruit, then three fruits inoculated with a 5-mm-diameter colonized disk of PDA incubated for 10 days and three fruits inoculated with blank PDA disk as control. After inoculation, the fruits were incubated in glass covers at room temperature. Symptoms began to appear after 2 days and were similar to those of naturally infected guava fruits after 5 days. Control fruits remained healthy. The same fungus was re-isolated from the inoculated fruits, but not control fruits, using the methods described above. Guava black spot disease caused by P. capitalensis has been previously reported in Egypt (Arafat 2018). Zhang et al. (2011) also reported detection of P. capitalensis in China on imported guava fruit with black spots inspected by the Airport Office of Ningbo Entry-Exit Inspection and Quarantine Bureau in Zhejiang province of China, but not collected from the field. To our knowledge, this is the first report that P. capitalensis is the pathogen of guava black spot disease in mainland China.

The sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae), is a destructive insect pest that damages sweet potatoes both in the field and during storage. To identify new environmentally friendly insecticides to control this insect pest, three assays (olfactory test, anti-feeding assay, and toxicity assay) were conducted to evaluate the efficacy and mode of action of 10 botanical insecticides against C. formicarius adults in 2015 and 2016. Of these 10 botanical insecticides, tea saponin, pyrethrins, and veratrine showed significant repellency in olfactory tests. Eight botanical insecticides showed anti-feeding effects in the feeding choice test. Five botanical insecticides had high toxicity. Among them, the lethal concentrations of rotenone were lowest followed by pyrethrins. The lethal time values of rotenone were shortest followed by nicotine. In conclusion, rotenone, pyrethrins, nicotine, and toosendanin have the potential to control C. formicarius adults. Of these, pyrethrins and toosendanin are more environmentally friendly than rotenone and nicotine and were identified as better insecticides to control C. formicarius.

Luohanguo, Siraitia grosvenorii (Swingle) C. Jeffrey, is a perennial cucurbitaceous plant that is an economically important medicinal and sweetener crop in Guangxi province, China. Surveys conducted during the summer to fall seasons of 2003-2004 in northern Guangxi showed symptoms typical of a viral disease, including leaf mottling, mosaic, vein clearing, curling, and shoestring-like distortion in the field. Mechanical inoculation of sap from leaves of symptomatic plants collected from the surveyed areas caused similar symptoms on tissue culture-derived healthy Luohanguo plants. Two sequences of 0.7 and 1.6 kb with 88 and 97% identity to Papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus (ZYMV) were amplified using reverse transcription-polymerase chain reaction (RT-PCR) with purified flexuous viral particles or total RNA extracted from the symptomatic Luohanguo leaves as templates with conserved degenerate potyvirus primers (1). To confirm the results, primers specific for PRSV (PP1/PP2, genome coordinates 4064-4083/5087-5069, GenBank Accession No X97251) and ZYMV (ZP1/ZP2, genome coordinates 5540-5557/7937-7920, GenBank Accession No L31350) were used to perform RT-PCR from the same RNA templates. The expected 1.0- and 2.3-kb fragments were amplified and they were 90 and 95% identical to PRSV and ZYMV in sequence, respectively. Watermelon mosaic virus was not detected. To our knowledge, this is the first report of the occurrence of PRSV and ZYMV in Luohanguo. Reference: (1) A. Gibbs et al. J. Virol. Methods 63:9, 1997.