Putting 'X' into context: the diversity of 'Candidatus Phytoplasma pruni' strains associated with the induction of X-disease.

Recurrent epiphytotics of X-disease, caused by 'Candidatus Phytoplasma pruni', have inflicted significant losses on commercial cherry and peach production across North America in the last century. During this period, there have been multiple studies reporting different disease phenotypes, and more recently, identifying different strains through sequencing core genes, but the symptoms have not, to date, been linked with genotype. Therefore, in this study we collected and assessed differing disease phenotypes from multiple U.S. states and conducted multi-locus sequence analysis on these strains. We identified a total of five lineages associated with the induction of X-disease on commercial Prunus species and two lineages that were associated with wild P. virginiana. Despite a century of interstate plant movement, there were regional trends in terms of lineages present, and lineage-specific symptoms were observed on P. avium, P. cerasus, and P. virginiana, but not on P. persica. Cumulatively, these data have allowed us to define 'true' X-disease-inducing strains of concern to the stone fruit industry across North America, as well as potential sources of infection that exist in the extra-orchard environment.

First Report of Aloe vera Rust Caused by Uromyces aloes in an Ornamental Nursery in the United States.

Aloe vera (L.) Burm. f. is a tropical evergreen perennial in the family Liliaceae. Native to the Arabian Peninsula, it is sold in Pennsylvania as an ornamental and for its medical and topical purposes due to its high levels of amino acids, anthraquinones, saponins, and vitamins A, B, C, E (Sahu et al. 2013). In February 2020, at an ornamental plant nursery in Lancaster County, Pennsylvania, 5 out of 15 mature A. vera plants in 15 cm pots showed symptoms and signs of rust on the leaves, exhibiting dark-brown erumpent pycnial spots with a chlorotic band surrounding the infected tissue that turned necrotic after three days of incubation at 20°C. Only the telial stage was present. Sori (n=25) were rounded, concentrically arranged, 0.2-3.7 mm, and covered by a brown epidermis. Teliospores (n=40) were amphigenous, orange-brown, globose to ellipsoidal, measuring (29.2) 30.4-36.1 (39.5) × (27.4) 27.6-30.1 (30.5) µm, with a wall thickness of 4-5 µm, and a persistent hyaline pedicel ranging from 5 to 57.1 µm in length and 5.2 to 9.3 µm in width. These measurements were comparable to the descriptions of Uromyces aloes previously reported from India (teliospore size 25-42.5 x 20-30 µm, wall thickness 3-5 µm, and pedicel size 25-95 x 5-6.25 µm), and South Africa (teliospore size 30-44 x 24-32 µm, wall thickness 4-6 µm, and pedicel size 6-20 µm) (Maier et al. 2007; Soni et al. 2011). Based on these morphological traits and the plant host, the causal agent was identified as Uromyces aloes (Cooke) Magnus (Pucciniaceae, Uredinales). The sample was also independently identified as U. aloes by the USDA APHIS PPQ Beltsville lab (Interception # APEMD200552555001) based on morphological characteristics. Teliospores were harvested with a sterile pin, transferred to a 1.5 ml tube with DNA extraction buffer (100 mM Tris-HCL, 10 mM EDTA, 1 M KCl, pH 8) and macerated using a plastic mini-pestle. The DNA was precipitated using isopropanol, washed with 70% ethanol, and reconstituted in 50 µl of PCR-grade water. The segment of the internal transcribed spacer region (ITS) was amplified using ITS4/ITS5 primers (White et al. 1990). The nuclear ribosomal small subunit (18S) was amplified with rust specific primers Rust18S-R (Aime 2006) and NS1 (White et al. 1990). The nuclear ribosomal large subunit (28S) was amplified with primers LR0R and LR7 (Vilgalys et al. 1990). Amplified PCR products were cleaned using ExoSap (Affymetrix, Santa Clara, CA) or QIAquick PCR Purification Kit (Qiagen, Valencia, CA) and sequenced at Penn State Genomics Core Facility. The nucleotide sequences were trimmed, analyzed, and aligned using Geneious 11.1.5 software (Biomatters, Auckland, NZ). The resulting 692-bp segment of the ITS, 1,633-bp segment of the 18S, and the 1,324-bp segment of the 28S regions were deposited in the GenBank database under accession numbers MT136509, MZ146345, and MZ146342, respectively. Based on GenBank BLAST analysis, a 529-bp fragment of our 28S product was found to share 98.87% (523/529) identity with U. aloes isolate WM3290 (DQ917740) from South Africa, with three nucleotide differences and three gaps between the two strains. Comparisons among ITS and 18S sequences could not be made because no ITS or 18S sequence data from U. aloes has previously been deposited in GenBank. To our knowledge, this is the first report of U. aloes from A. vera in the United States. Infected plants were confined inside a greenhouse and have been destroyed. Since the plants were purchased from either Ontario, Canada or Florida, the extent of infection in the United States is unknown.

Clinical And Morphological Improvement Of Lupus Nephritis Treated With Rituximab.

AIM: TO assess the effects of rituximab (RTM) therapy on clinical and morphologic activity of lupus nephritis (LN). MATERIAL AND METHODS: The study included 45 patients with confirmed diagnosis of systemic lupus erythematosus (SLE), unaffected by previously received standard therapy with glucocorticoids (GCs) and cytostatics. The disease activity was assessed using Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI 2K); to assess the LN activity we used the SLICC RA/RE index. Forty-five patients with LN were given puncture renal biopsy prior to prescribing RTM; 16 patients had repeated renal biopsy 1 year and more after beginning the anti-B-cell therapy. LN was graded histologically in accordance with the WHO classification (2003) with indices of activity (AI) and chronicity (CI). RESULTS: The predominant number of patients had class III - IV of LN. The repeated renal biopsies demonstrated that LN had undergone a transition into a more favourable morphologic class, which was associated, in most of these cases, with a positive therapeutic effect. The follow-up dynamics showed a statistically significant reduction of AI (p=0.006), and no statistically significant changes in the CI (p = 0.14). CONCLUSION: The long-term follow-up in the study has showed that repeated courses of anti-B-cell therapy with RTM have a positive effect both on SLE activity and generally on the renal process. The reduction of the morphologic class of LN as assessed in the repeated renal biopsies is a convincing proof for this. Eleven out of 16 patients experienced transition of the morphologic class into a more favourable type, which in most cases was combined with lower AI (p = 0.006). We found no evidence of increase in the CI (p = 0.14).

Some peculiarities of pulmonary clearance mechanisms in rats after intratracheal instillation of magnetite (Fe3O4) suspensions with different particle sizes in the nanometer and micrometer ranges: are we defenseless against nanoparticles?

We studied differences between phagocytic responses to nanoparticles (NPs) versus microparticles in the pulmonary region by synthesizing magnetite of different sizes and instilling suspensions of these particles intratracheally into rats' lungs. Ten and 50 nm particles caused a greater increase in cell counts of the bronchoalveolar lavage fluid (BALF) than the instillation of microparticles. The response to 10 nm particles was weaker than to 50 nm ones, and the smaller NPs were more cytotoxic; both were more cytotoxic than the microparticles. Phagocytic activity was also studied using optical and atomic force microscopy. Phagocytes were more "loaded" in the lungs instilled with 10 nm particles as compared with those instilled with 50 nm particles; NPs of both sizes were engulfed more avidly than microparticles. We found in a separate comparative experiment that magnetite NPs were more cytotoxic than titanium dioxide and quartz suspensions having particle size distribution typical of industrial dusts.

Ratios of Cells With and Without Virulence Genes in Rhodococcus fascians Populations Correlate with Degrees of Symptom Development.

Rhodococcus fascians, a gram-positive phytopathogenic bacterium, causes fasciation and leafy galls on a wide range of monocotyledonous and dicotyledonous plants for which it requires the plasmid-borne fas operon. Strains isolated from symptomatic plants over a 20-year-period exhibited a high degree of variability when their virulence was assessed on garden pea seedlings. Polymerase chain reaction amplification of the fas-1 and fasR virulence genes from randomly chosen single colonies showed that many strains consisted of two subpopulations, of which one had lost these genes. Inoculation of pea seedlings with mixtures of fas-1-positive and -negative cells that originated from the same strain demonstrated a strong correlation (Pearson's r ≥ 0.9205) between the proportion of cells in the inoculum carrying the fas-1 gene and the severity of disease symptoms. The minimal concentration of fas-1-positive cells required for the development of small lateral shoots on pea seedlings was 2.5 × 104 CFU/ml (P ≤ 0.008), while the overall suppression of main stem growth was observed at 2.5 × 105 CFU/ml (P ≤ 0.019). These observations underline that care should be taken when the virulence of clinical R. fascians strains is evaluated.