Black Leg and Chlorotic Leaf Spot Occurrence on Brassicaceae Crop and Weed Hosts

Black leg (caused by Plenodomus lingam and P. biglobosus) and chlorotic leaf spot (caused by Pyrenopeziza brassicae) are economically important fungal diseases of Brassicaceae crops. Surveys of seed fields and weed hosts were conducted to understand the distribution and prevalence of these diseases in Oregon after black leg and chlorotic leaf spot outbreaks occurred in Brassicaceae crops in 2014. Post-harvest black leg ratings for these diseases were conducted in 2015 and 2016 in seed fields of canola, forage rape, and turnip. Black leg incidence was greater in turnip (51%) compared to canola (29%) and forage rape (25%). The overall average disease incidence was greater on seed crops harvested in 2015 (46%) compared to crops harvested in 2016 (28%). A disease survey of wild Brassicaceae plants was conducted along Interstate 5 in Oregon. Brassicaceae weed population sites were identified and 40 sites were sampled for these diseases. Black leg and chlorotic leaf spot were present in 60% and 45%, respectively, of the sampled sites. Both species of Plenodomus were detected in weed populations with P. lingam being the predominant species recovered (95%). The northernmost sample site with black leg was found less than 32 km from the Oregon-Washington border, and southernmost site occurred within 32 km of the Oregon-California border. Chlorotic leaf spot was detected less than 32 km from Oregon-Washington border, whereas the southernmost detection was approximately 164 km from the Oregon-California border. Based on this study, infected crop residues and weed hosts may facilitate persistence and spread of these pathogens.

First report of Leptosphaeria biglobosa ‘brassicae’ causing Black Leg on Brassica rapa subsp. pekinensis in China

Chinese cabbage [Brassica rapa L. subsp. pekinensis (Lour.) Hanelt] is a major leafy vegetable crop grown in China and eastern Asia (Fordham and Hadley 2003). In December 2018, black leg symptoms were observed on of “Qingza No.3” of Chinese cabbage during harvest, Chibi (29°46′37.38′′N, 114°05′6.88′′E), Hubei, China. Symptoms were first noted in late Nov. as black spots on leaf petioles and basal stems. Then, black spots enlarged as oval or irregular-shaped grayish lesions. Finally, lesions enlarged and coalesced with black pycnidia were observed, and some diseased leaves became blighted. The disease incidence was about 80% in three fields surveyed (~2 ha in total). Diseased plant tissues were surface-sterilized, and incubated on potato dextrose agar (PDA) plates at 20°C for 4 days. Three fungal isolates, namely EP9-19, EP9-22 and EP9-26, were obtained from five of the diseased samples; all produced fluffy, white aerial mycelia and a yellow pigment on PDA. After 14 days, black-brown and globose pycnidia were produced, approximately 150 μm in diameter (n = 50). In addition, pink pycnidiospore ooze was observed on the top of pycnidium after 20-day culturing on a V8-juice (20%) agar. Conidia were cylindrical and hyaline, with the mean size of 4.6 × 2.7 μm (n = 50). Two fungal species have been reported to cause blackleg on Brassica crops (Williams and Fitt 1999), i.e. Leptosphaeria maculans and L. biglobosa. The former is much more destructive, but is not present in China. These isolates had morphological characteristics matching those of L. biglobosa (Williams and Fitt 1999). The genomic DNA of isolate EP9-22 was extracted and sequenced for its actin, β-tubulin and the internal transcribed spacer (ITS) region of ribosomal DNA as described by Vincenot et al. (2008). Sequences of ITS (GenBank accession no. MN238766), actin (MN242213) and β-tubulin (MN242214) for isolate EP9-22 showed 100%, 99.67%, and 97.93% identity to the corresponding regions of L. biglobosa ‘brassicae’ strain IBCN89 (Vincenot et al. 2008). In addition, the phylogenetic analysis also indicated that isolate EP9-22 belonged to L. biglobosa ‘brassicae’. The pathogenicity test was performed according to established protocols (Balesdent et al., 2005). Cotyledons of the 15-day-old Chinese cabbage seedlings (cultivars Xiaoza No.55 and Hualiangzao No.5) were wound inoculated with 10 μl pycnidiospore suspension (1 × 107 conidia/ml) of the three isolates, with 20 cotyledons per isolate, respectively, and 20 cotyledons wound inoculated with sterile water served as a control group. The treated seedlings were maintained at 20°C and 100% relative humidity with a 12-h photoperiod. The experiment was repeated twice. At 7 days after inoculation, necrotic lesions became visible surrounding inoculation sites for the three isolates, while the control group remained healthy. Fungal isolates showing a similar colony morphology to the originals were re-isolated from ten diseased cotyledons but not from the control cotyledons. Based on these results, L. biglobosa ‘brassicae’ was shown to be the causal agent of blackleg on Chinese cabbage in China. We believe that this disease has historically often been misidentified as ‘anthracnose’ by local famers. The threat from L. biglobosa to the production of Chinese cabbage has been assessed. This accurate identification of the causal pathogen is a critical first step towards the development of disease management strategies.

First Report of Pectobacterium polaris Causing Soft Rot and Black Leg of Potato in Russia

Blackleg and soft rot of potato (Solanum tuberosum) were monitored in the Central European part of Russia within a period of 2012- 2019. Symptoms included decay of tubers, blackening of stem vascular bundles, and partial yellowing of leaves. The disease causes serious potato yield losses in the field and storage. Pectobacterium parmentieri, P. brasiliense, P. versatile (syn. Ca. Pectobacterium maceratum), P. carotovorum, P. atrosepticum, Dickeya dianthicola, and D. solani are considered as main causal agents of soft rot and blackleg disease in Russia (Voronina et al. 2019, Ngoc Ha et al., 2019, Shirshikov et al. 2018, Kornev et al. 2012). Potato plant samples collected in commercial fields in routine plant health assay were used for bacteria isolation on crystal violet pectate agar (CVP) (Helias et al. 2012) as described previously (Voronina et al. 2019). Bacterial colonies producing pitting on CVP were re-isolated and purified on nutrient broth yeast extract medium. DNA of bacterial isolates was extracted, and polymerase chain reaction (PCR) amplifications were performed using gapA primers (Cigna et al. 2017) followed by sequencing. DNA sequence alignment showed that the isolates F099, F100, F106, F109, and F118 were identical (deposited as part of NCBI Ref.Seq. for F109 NZ_RRYS01000004.1, locus KHDHEBDM_RS06360) and grouped together with the type strain Pectobacterium polaris NIBIO1006T (CP017481), a new species described as a potato pathogen (Dees et al. 2017). These strains were negative in diagnostic PCR assays using specific primers Y45/Y46 for the detection of P. atrosepticum, Br1f and L1r for P. brasiliense (Duarte et al. 2004), and ADE1/ADE2 for Dickeya sp. (Nassar et al. 1996). To further validate the identification, strain F109 of P. polaris was selected for genome sequencing. The genome of P. polaris strain F109, (NCBI Reference Sequence NZ_RRYS00000000.1) reveals >99% sequence similarity with type strain P. polaris IPO_1606 (GenBank accession GCA_902143345.1). The strain F109 was deposited to All-Russian Collection of Microorganisms under number VKM V-3420. Thus, the characterization of five isolates provided evidence that a previously unreported pathogen was present in the surveyed fields. The isolates were uniform in genetic and physiological properties; they were gram negative, facultative anaerobes with pectinolytic activity, negative for oxidase, urease, indole production, gelatin liquefaction. All isolates were catalase positive, produced acid from lactose, rhamnose, saccharose, xylose, and trehalose, and were tolerant to 5% NaCl, unable to utilize malonate and citrate. All the isolates grew at 37°C. All isolates caused soft rot symptoms on 10 inoculated potato tubers. They produced typical black leg rot symptoms in young potato plants inoculated with 107 CFU/ml of the pathogen by stem injection and incubated at 25°C for 48 h. The bacteria were re-isolated successfully from symptomatic potato and pathogen confirmed by gapA sequencing to complete Koch’s postulates. To our knowledge, this is the first report of blackleg and soft rot caused by P. polaris on potato in the Russian Federation. According to the data of commercial diagnostic laboratory “PhytoEngineering” (Moscow region), P. polaris occurred in 5% potato seed stocks harvested in 2017-2019 in the Moscow region. This finding may indicate that new Pectobacterium strains have adapted to a diverse environment, which is consistent with widespread distribution of commercial seed potatoes. The author(s) declare no conflict of interest. Funding: This work was supported by Russian Science Foundation grant #16-16-00073.

Retrospective study on livestock vaccine coverage and trends in Digelu-tijo district, Arsi zone

Ethiopia has huge numbers of livestock hampered with high prevalence of infectious disease due to poor disease prevention and control. A five-year retrospective study was conducted to collect data on commonly diagnosed bacterial and viral disease and associated vaccine available at district government veterinary clinic in 2019. The commonly encountered bacterial and viral cattle diseases recorded in the case record book were LSD, CBPP Black leg, Anthrax, Bovine pasteurellosis, and Mastitis. Sheep and goat pox disease, Ovine Pasteurellosis, PPR, CCPP, and anthrax were the common diseases of sheep and goat in the study district. Regarding diseases of poultry, New castle, Infectious Bursal Diseases (Gumboro), Infectious coriza, chicken pox, Coccidiosis, Fowl Typhoid, Fowl Cholera, and Marex are the major once. The commonly available vaccines in the study district were LSD, Black leg, Anthrax, Bovine pasteurellosis, Ovine pasteurellosis, Sheep and Goat Pox, PPR, and vaccine for chicken disease like New castle disease vaccine, Gumboro, Fowl Pox, Fowl typhoid and Fowl cholera were used. Vaccination coverage for Lumpy Skin Disease, Sheep and Goat pox and Newcastle viral diseases were good compared with other diseases. The majority 36% of the population of cattle were vaccinated for LSD in 2019 and the lowest 16% in 2015.The lower portion of shoat 8% and half of the population 50% were vaccinated in 2017 and 2019 respectively. Maximum proportion of Newcastle and Gumboro vaccination coverage were 53% and 42%. The vaccination trends for most of the vaccines were fluctuating from year to year whereas the vaccination trend for LSD was increasing from year to year.

Commodification

I explore the depiction of the Miracle of the Black Leg by Saints Cosmas and Damian. This narrates the miraculous cure of a white verger with a diseased leg after the grafting of a leg from a dead African man onto his amputated stump. I show how the Greek, Latin and Catalan legends of this miracle give rise to different conceptions of the black subject defined either as a ‘Moor’ or as an ‘Ethiopian’ and I look at the violent sixteenth-century image of the mutilated African man, worked up by Isidro de Villoldo in Valladolid (1547) and the ways in which it was interpreted by other sculptors in Castile, and show how it drastically departs from the original literary and visual sources examined. I believe that there is a reference to the mutilation of limbs or ears suffered by fugitive slaves and I construct an account of the treatment of slaves.