Exigua Var Research Articles

Use of Pseudomonas protegens to Control Root Rot Disease Caused by Boeremia exigua var. exigua in Industrial Chicory (Cichorium intybus var. sativum Bisch.).

Boeremia exigua var. exigua is a recurrent pathogen causing root rot in industrial chicory. Currently, there is no chemical or varietal control for this disease, and thus, management strategies need to be developed. This study determined the biocontrol effect of strains of Pseudomonas protegens bacteria with antimicrobial compounds on the fungus B. exigua var. exigua under in vitro, in vivo, and field conditions. In addition, root colonization by these bacteria was estimated by the phlD-specific PCR-based dilution end point assay. Eighteen isolates of Pseudomonas spp were evaluated, and the strains that showed the greatest in vitro inhibition of fungal mycelial growth (mm), Ca10A and ChB7, were selected. Inoculation with the strain ChB7 showed less severity (necrotic area) under in vivo conditions (root trials) compared with the control inoculated with the pathogen (p ≤ 0.05). The molecular analysis revealed that the root colonization of plants grown in pots was equal to or greater than 70%. Similar levels were observed in the field trials conducted at the Selva Negra and Canteras experimental stations (2015-2016 season), with values ranging from 85.7 to 70.5% and from 75.0 to 79.5%, respectively. Regarding yield (ton ha-1), values were higher in the treatments inoculated with strains Ca10A and ChB7 (p ≤ 0.05) at both experimental sites, while a lower incidence and severity of root rot were observed at Selva Negra. These results suggest that the Chilean strains of P. protegens are a promising tool for the control of root diseases in industrial chicory.

Characterization of Boeremia exigua causing stem necrotic lesions on Luobuma in northwest China

Luobuma (Apocynum venetum, Poacynum pictum, and P. hendersonni) are perennial herbs widely used in the textile and medical industries and ecological restoration. In the summer of 2020, reddish-brown or off-white sunken shape necrotic lesions were observed on the stems and shoots of seven Luobuma ecotypes grown in the field in Yuzhong County, Gansu province of China, which is a limiting factor that affects the growth, function and application of Luobuma. To make clear whether the new symptoms were caused by a novel pathogen, a combined research in field and greenhouse was conducted. Based on the morphological and molecular analysis results, the pathogen causing the necrotic lesions was identified as Boeremia exigua var. rhapontica. The incidence and disease index of the seven ecotypes in the field ranged from 11.49 to 33.68% and 6.63 to 23.01, respectively, from 2020 to 2021. The results showed that the disease severity gradually increased with the growing season. According to the pathogenicity analysis of the eight ecotypes in the greenhouse, the ecotypes Pp-BMK and Pp-BMH were susceptible, while ecotype Pp-BMQ was resistant to Boeremia exigua var. rhapontica infection. Thus, the present study provides a theoretical basis for preventing and controlling the stem and leaf necrotic lesions disease on Luobuma by planting resistant varieties/ecotypes. To our knowledge, this is the first report of stem necrotic lesions and leaf spots on Luobuma caused by B. exigua var. rhapontica.

Оцінка стійкості картоплі до збудників хвороб, поширених в Україні

Goal. To evaluate and select potato varieties of domestic selection, resistant against the causative agents of cancer — Synchytrium endobioticum (Schilb.) Perc, phomous rot — Phoma exigua var. exigua (Desm.), alternariosis — Alternaria solani (Ell. & Mart.) and Alternaria alternata (Fries) Keissler. To improve promising potato varieties for introduction in seats of these diseases. Methods. Laboratory evaluation of potato varieties on artificial infectious backgrounds: causative agents of cancer, phomous rot, and alternariosis. Improvement and reproduction of potato varieties were carried out by the method of in vitro culture on Murasighe-Skug nutrient medium. Results. According to the results of laboratory tests in 2019–2021, 8 varieties resistant to all pathotypes of the causative agent of cancer were selected from 28 potato varieties; 4 — to phomous rot; 6 — to alternariosis. 14 potato varieties of domestic selection, which had signs of resistance to several diseases, were improved. Conclusions. According to the results of 3-year laboratory tests, potato varieties were selected with resistance to potato cancer pathogens — Bazys, Hlazurna, Rodynna, Misteria, Santarka, Solokha, Strumok, and Khortytsia; phomous rot — Ariya, Misteriya, Rodynna, and Sontsedar; alternariosis — Hlazurna, Kalynivska, Poliske dzhrelo, Teteriv, Fantasiya, and Yavir. 14 varieties of potato of domestic selection from the State Register of plant varieties suitable for cultivation in Ukraine in 2000–2010, which were resistant to diseases for many years, were improved and recommended for use in integrated systems of plant protection against the investigated causative agents of cancer, phomous rot and alternariosis on the territory of Ukraine.

Population Genetic Analysis of the Threatened Plant Leavenworthia exigua var. laciniata (Brassicaceae) Reveals Virtually No Genetic Diversity and a Unique Mating System

Leavenworthia (Brassicaceae) has served as a model group for investigating the evolution of mating systems in plants, yet several Leavenworthia species remain understudied. One such taxon is Leavenworthia exigua var. laciniata, one of three varieties of L. exigua, a winter-annual plant endemic to the central United States. Because L. exigua var. laciniata occupies a narrow geographic range and is experiencing major habitat loss, it was recently listed as threatened; however, little is known about its genetic diversity and implications for conservation. We conducted a range-wide population genetic study of L. exigua var. laciniata and L. exigua var. exigua to understand: (1) levels of genetic diversity within and among populations, (2) whether L. exigua var. laciniata is genetically distinct from L. exigua var. exigua, and (3) implications for conservation. L. exigua var. laciniata showed identical genotypes at all 16 microsatellite loci across most of its range, fixed heterozygosity at some loci, and significant heterozygote excesses, consistent with a lack of recombination associated with an asexual mating system, which has not been documented previously in Leavenworthia. Because L. exigua var. laciniata is an annual and the same genotype occurs across multiple populations, asexuality may be caused by apomixis, asexual reproduction via seed. In contrast, most populations of L. exigua var. exigua demonstrated population genetic patterns consistent with a self-compatible mating system. Because L. exigua var. laciniata is morphologically, geographically, and genetically distinct, it should be recognized as an evolutionarily significant unit for conservation. We recommend maintaining large population sizes to conserve evolutionary potential in L. exigua var. laciniata, as the likelihood that facultative sexual reproduction may occur may be greater in larger populations. Additional research in L. exigua var. laciniata is needed to confirm the occurrence of asexuality and apomixis, clarify its reproductive isolation from other taxa, and to understand whether it exhibits residual sexual reproduction, epigenetic variation, or phenotypic plasticity to help it persist in response to environmental variation. In the future, L. exigua var. laciniata may serve as an important model in which to investigate the conservation of threatened plant species with little genetic variation in a changing climate.

First report of Boeremia exigua var. exigua causing branch blight on walnut in China.

Walnut (Juglans sinensis L.) is an important economic tree. Its fruit are rich in omega-3 essential fatty acids, which are valuable nutritionally (Cheon et al, 2013). In March 2019, severe branch blight of walnuts (cv. Qingxiang) were observed in two fields in Ganquan Town, Gansu Province, China (N 33°56'/E105°44'). The incidence was about 3% among 10,000 walnuts. Disease symptoms included fusiform or oval black lesions gradually expanded on the branches, blight and dieback of branches, reddish brown dead branch bark with lots of black small spots (pycnidia), and defoliation. To isolate pathogen, 30 diseased tissues collected from different trees were disinfected with 0.1% HgCl solution for 1 min, rinsed in sterilized water 3 times, and placed on potato dextrose agar (PDA) at 25℃ in the dark. About three days later, 4 fungal isolates (3-3, 3-6, 3-9 and H3) with similar morphological characteristics were obtained. Their colonies, with regular margin on OA, 6.1~6.8 cm diam. after 7 days, were loose, greenish olivaceous to olivaceous grey, velvety, floccose to woolly. The conidia (n=60) were 4.77 to 8.84 μm long (mean = 6.88 μm; SD ± 0.91 μm) × 1.71 to 3.89 μm wide (mean = 2.81 μm; SD ± 0.53 μm), cylindrical, ellipsoidal to oblong, hyaline and aseptate. Pycnidia (n=25) were 76.66 ~ 132.86μm diam. (mean = 102.93 μm; SD ± 12.15 μm), variable in shape and size, mostly globose to subglobose. These characteristics were similar to B. exigua var. exigua (Boeremia et al, 2004). Pathogenicity tests of four isolates were performed 3 times on 5 healthy 2-3 years old walnuts (cv. Qingxiang). Plants were wounded by insect needle No.6 and inoculated with 5 mm mycelium block grew on PDA medium or PDA medium as control and kept moist in climatic cabinet (> 85% RH, 25°C). After 3 days, oval black lesions were occurred on branches and gradually expanded, but control was asymptomatic. And original isolates were re-isolated from these diseased shoots. Genomic DNA of four isolates were extracted, and the internal transcribed spacer (ITS), β-tubulin (tub2) and RNA polymerase II second largest subunit (rpb2) gene were amplified and sequenced using the primers ITS1/ITS4, Btub2Fd/Btub4Rd and RPB2-5F2/fRPB2-7CR (White et al, 1990; Woudenberg et al, 2009; Chen et al, 2015), respectively. Sequences were deposited in GenBank (accession no. ITS: MT154621, MT154622, MT154623, MT154624; tub2: MT223481, MT223482, MT223483, MT223484; rpb2: MW448152, MW448153, MW459982, MW459983), and compared with available sequences in NCBI. Results showed that ITS of four isolates have 100% sequence identity to Boeremia spp., tub2 and rpb2 have 100% sequence identity to B. exigua var. exigua (GenBank accession no. MN983734, MN983315) and B. exigua var. linicola (GenBank accession no. MN983785, MT920619). According to host specificity (Boeremia et al, 1976). A 106 conidium/mL spore suspension of four isolates or sterile water were inoculated on stem base of two-month old flax seedlings, placed in climatic cabinet (> 85% RH, 25°C) for moisturing and repeated three times. After two weeks, all inoculated plants still were asymptomatic, indicated that four isolates aren't B. exigua var. linicola. Therefore, they were identified as B. exigua var. exigua based on morphological characteristics, molecular analysis and pathogenicity tests. To our knowledge, this is the first report of B. exigua var. exigua causing walnut branch blight worldwide, which will provide further guidance for prevention and control of walnut branch blight.

Synthetic Promoters from Strawberry Vein Banding Virus (SVBV) and Dahlia Mosaic Virus (DaMV).

We have constructed two intra-molecularly shuffled promoters, namely S100 and D100. The S100 recombinant promoter (621bp) was generated by ligation of 250bp long upstream activation sequence (UAS) of Strawberry vein banding virus (SV10UAS; - 352 to - 102 relative to TSS) with its 371bp long TATA containing core promoter domain (SV10CP; - 352 to + 19). Likewise, 726bp long D100 promoter was constructed by fusion of 170bp long UAS of Dahlia mosaic virus (DaMV14UAS; - 203 to - 33) with its 556bp long core promoter domain (DaMV4CP; - 474 to + 82). S100 and D100 promoters showed 1.8 and 2.2 times stronger activities than that of the CaMV35S promoter. The activity of the promoters is comparable to that of the CaMV35S2 promoter. Transcript analysis employing qRT-PCR and histochemical assays supported the above findings. Abscisic acid and salicylic acid induce the activity of the D100 promoter. Leaf protein obtained from Nicotiana tabacum plant expressing NSD2 gene (Nigella sativa L. defensin 2) driven by the D100 promoter showed antifungal activity against Alternaria alternata and Phoma exigua var. exigua and antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus. Strong S100 and D100 promoters have potential to become efficient candidates for plant metabolic engineering and molecular pharming.

Terpestacin, a toxin produced by Phoma exigua var. heteromorpha, the causal agent of a severe foliar disease of oleander (Nerium oleander L.)

Since 1987, several cytochalasins were isolated from Phoma exigua var. heteromorpha, the causal agent of foliar blight disease of oleander (Nerium oleander L.), and chemically and biologically characterised. During the purification process of a large-scale production of cytochalasins A and B, necessary to continue the study on their anticancer activity, a metabolite having a different carbon skeleton compared to that of cytochalasans, was isolated. It was identified as terpestacin, a well-known toxic fungal stestertepenoid, isolated for the first time from P. exigua var. heteromorpha, by spectroscopic investigation (essentially 1D and 2D 1H and 13C-NMR and ESI MS) and optical methods in comparison with the literature data. Terpestacin and some its derivatives (including a natural one, fusaproliferin) were prepared and tested for their biological activity. Terpestacin and fusaproliferin had some inhibitory effects on seed germination of Phelipanche ramosa, whereas none of the compounds caused phytotoxic effects on weed leaves.

Limitation of the distribution of the latent form of potato phomosis with the use of biofungicides

Goal. To establish the spread of the latent form of the phomosis pathogen in the western region of the Forest-Steppe zone and to study the possibility of crop protection through the use of biofungicides.
 Methods. In the process of work used laboratory (cultivation of pathogens) and field (analysis, processing of tuber material).
 Results. The results of research conducted during 2019—2020 to detect latent infection of phomosis rot of potatoes in the western part of the forest-steppe zone of Ukraine (Zakarpattia, Chernivtsi, Ivano-Frankivsk regions) are presented. Within two years, the highest damage to tubers by latent phomosis infection was observed in varieties Yavir and Vodogray in the Ukrainian Carpathians (Ivano-Frankivsk region, Verkhovyna district, Bystrets village; Zakarpattia region, Mizhhirya district, Maidan village; Zakarpattia region, Rakhiv district, Yasinya village; Chernivtsi region, Vyzhnytskyi district, Berehomet village), which reached 25—33 and 21.0—23.0%, respectively. In the plain zone of Chernivtsi region (Hertsaiv district, Bukivka village; Novoselytsia district, UkrNDSKR IZR) a significantly lower percentage of tuber lesions with a latent form of the disease was observed. The minimum rates of tuber damage, both latent form of phomosis and with existing external signs, were observed in the variety Slovyanka and were in the plain zone 4.5—5.5% and 7.0—8.0 in the mountain. When treating tubers with biofungicides, the least pathogen tuber damage was observed in the variants using Trichodermin-Bio, PhytodoDoctor and Planriz, where the number of infected tubers was 10.0, 11.0 and 12.5%, respectively. In the control variant, the percentage of affected tubers with latent form of phomosis was 2.1—3.2 times higher than in the experimental ones. The effectiveness of biofungicides was greatest when using Trichodermin-Bio and PhytoDoctor and was 68.3 and 65.1%, respectively. Less effective drug against the latent form of phomosis, compared with other options was Hetomic, where its technical efficiency was 52.4%.
 Conclusions. The causative agent of phomotic rot of potatoes (Phoma exigua var. Exigua) in latent form is a widespread pathogen in the western part of the Forest-Steppe zone. To limit the spread of latent infection of phomos, biological drugs Hetomik (0.4 kg/ha) were used, Gaupbsin (5 l/t), Planriz (2 l/t), Trichodermin-Bio (2 l/t), PhytoDoctor (0.3 l/t), which helped to reduce the damage to the tubers by a latent form of the disease by 2.1—3.2 times compared to the control.

Use of cumin and lavender essential oils to control phoma exigua var. foveata on potato during storage

The antifungal activity of essential oils against Phoma exigua var foveata, was investigated by analyzing its inhibitory effect on the gangrene of potato tubers. The results showed that mycelium growth and spore germination of Phoma was suppressed by treatment with essential oils, and the inhibitory effect strongly correlated with the concentration of essential oils used in this study. The effectiveness of post-harvest treatment with essential oils was studied for induced resistance to Phoma rot in tubers of two potato varieties (Kolobok and Sante). The results showed the fungicidal effect of cumin and lavender essential oils against phomosis at concentrations of 0.1, 0.2, and 0.4, significant inhibition of mycelium growth (18.1-100%), and viability of conidia (12.8-100%) compared to the control. Moreover, both oils at a concentration of 0.4% caused 100% inhibition of mycelium growth and spore germination. Treatment with oils at a concentration of 0.01-0.04 l/t significantly reduced the degree of damage to tubers infected with phomosis. However, cumin essential oil at a concentration of 0.04 l/t had the greatest effect 97.1% compared to lavender oil 95.4%.

First report of Boeremia exigua var. exigua causing Black Spot-like symptoms on commercially grown soybean in Germany.

Soybean (Glycine max [L.] Merr.) is economically the most important protein crop grown worldwide. However, Europe largely depends on soybean imported from the Americas (European Commission 2019; Haupt and Schmid 2020). In Germany, soybean production was not formally recorded before 2016, but since then a steady increase along with an expansion of the growing area from the south of Germany to northern states occurred. In 2019 an area of 29,000 hectares was under soybean cultivation (Federal Ministry of Food and Agriculture (Germany) 2019). In the state of North Rhine-Westphalia (NRW, western part of Germany) farmers have started in recent years to cultivate soybean, making it increasingly important to monitor pathogens associated with this new crop. At the beginning of October 2019, shortly before harvest, rows of black spots on pods and stems of soybean plants cv. Viola throughout a field site near Jülich (NRW) were observed. Close observation identified them as pycnidia with similarity to symptoms reported from soybean in Austria in 2015 (Hissek and Bedlan 2016). The collected samples were thoroughly surface sterilized (two washes with 70 % EtOH, a rinse in 0.5 % sodium hypochlorite solution and a final wash in sterile double distilled water) and placed on plates containing potato dextrose agar (PDA) at 22 °C in the dark. Fungal colonies were transferred to malt extract agar plates (MEA) and examined by microscopy. Thus, 34 of 41 isolates looked morphologically similar, producing colonies that appeared dark grey with white aerial mycelium and round to irregular margins. A single spore isolate was generated and designated IPP1903. Spores derived from IPP1903 were unicellular and mostly oblong to cylindrical with a mean width of 2.6±0.3 µm and a mean length of 5.9±0.8 µm (N=50, mean value ± standard deviation). Colonies on MEA were 5.4 to 5.8 cm in diameter after growth for seven days at 20 to 25°C with a photoperiod of 12 h and 3.3 to 3.7 cm in diameter after growth for seven days in the dark at 22°C. These morphological observations led to the conclusion that the isolate may belong to the genus Phoma. To test this hypothesis, we performed a drop test with 5 M NaOH which is used routinely to check for the presence of a genus-specific metabolite. We observed a change in color, indicating a positive test result. The color change was even more pronounced on the plates incubated in the light, further confirming the presence of "metabolite E" (Boerema et al. 2004; Kövics et al. 2014). Next, DNA was extracted and PCR was performed with primers specific for ITS regions (GenBank MT397284), LSU (MT397285), rbb2 (MT414713) or tub2 (MT414712). Sequencing results of PCR products were used to create a combined phylogenetic tree, including sequences published previously (Chen et al. 2015). Our sequencing results together with the morphological observations clearly identified the fungal isolate to be Boeremia exigua var. exigua. The isolate is publicly available in the CBS collection of the Westerdijk Fungal Biodiversity Institute with the accession no. CBS 146730. Koch's postulates were fulfilled by inoculating a spore suspension of the isolate IPP1903 (5x105 ml-1 in 0.05% Tween 20 solution in distilled water) onto healthy primary leaves of twenty 14 days old soybean plants of the cultivar Abelina. While the mock-inoculated plants (inoculated with 0.05% Tween 20 solution in distilled water) stayed healthy, the inoculated plants developed lesions on the leaves after seven days. Six weeks after inoculation the fungus could be reisolated from cuttings of the infected leaves after surface-sterilization. Fungal colonies were confirmed to be B. exigua var. exigua by morphological examination and via NaOH drop test. To our knowledge, this is the first report of B. exigua var. exigua causing disease on commercially grown soybean in Germany.

First report of Boeremia exigua var. exigua as a pathogen of Cycas circinalis in India

In late summer 2016, necrotic lesions on leaves were observed on Cycas circinalis L. plants, in the Agri-Horticultural Society of India, Alipore Road, Kolkata (located at 22˚53'N; 88°33' E), West Bengal. Based on morphology, DNA sequencing and pathogenicity testing the causal pathogen was identified as Boeremia exigua var. exigua, which is the first report on C. circinalis in India.

The use of chitosan against potato gangrene during storage

Potato gangrene is a very dangerous disease developing during storage and can lead to serious crop losses. The main control of this pathogen is reported by the post-harvest use of fungicides. However, the pathogen resistance to fungicides and public concerns about food safety require the search for new alternatives to fungicides, potentially less harmful to human health and the environment. The antifungal influence of chitosan against Phoma exigua var foveata and analyzing its inhibitory effect on the gangrene of potato tubers were investigated. The results showed that the growth of the mycelium and the germination of Phoma spores were suppressed by chitosan treatment, and the inhibitory effect was strongly correlated with the chitosan concentration. The effectiveness of post-harvest chitosan treatment has been studied for induced resistance to Phoma rot in tubers of two potato varieties (Kolobok and Santa). In vivo studies have shown that chitosan treatment at a concentration of 0.5 or 1% effectively combated gangrene potato tubers inoculated with a suspension of Phoma spores. However, treatment with chitosan at a concentration of 1% caused phytotoxicity of potato tubers. Chitosan increased the activity of peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase in tubers. This study suggests that the influence of chitosan may be related to the induced resistance of potato Phoma rot, and the use of chitosan may be a promising agent as a natural fungicide for partial replacement of synthetic fungicides to protect potato tubers during storage.

Standards to be withdrawn

EPPO BulletinVolume 48, Issue 3 p. 538-539 CorrigendumFree Access Standards to be withdrawn This article corrects the following: PM 3/22 (2) Phytophthora fragariae: inspection Volume 43Issue 3EPPO Bulletin pages: 395-395 First Published online: November 19, 2013 First published: 07 December 2018 https://doi.org/10.1111/epp.12540AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat The following Standards from the Series PM 3 are withdrawn: PM 3/22(2) Phytophthora fragariae: Inspection PM 3/23(1) Phoma exigua var. foveata. Inspection and test methods PM 3/24(2) Chrysanthemum stunt viroid. Inspection methods PM 3/31(1) Rubus viruses. Inspection and test methods PM 3/36(1) Phaeoisariopsis griseola. Inspection and test methods for bean seeds PM 3/37(2) Tilletia indica. Inspection methods for wheat seeds PM 3/46 (1) Methyl bromide fumigation of citrus and other hosts plants to control Aleurocanthus woglumi PM 3/47 and PM 3/50 have been revised to withdraw the schedule with methyl bromide. These are moved to series PM 10 and published in this issue of the EPPO Bulletin). The following Standard from the Series PP1 is withdrawn: PP 1/277 Insecticide co-formulated mixtures withdrawn as replaced by PP 1/306 (1) General principles for the development of co-formulated mixtures of plant protection products All the PP3 Standards Environmental risk assessment scheme for plant protection products are withdrawn: Decision-making scheme for the environmental risk assessment of plant protection products Chapter 1: Introduction Chapter 2: Guidance on identifying aspects of environmental concern Chapter 3: Soil Chapter 4: Ground water Chapter 5: Surface water Chapter 6: Aquatic organisms Chapter 7: Soil microflora Chapter 8: Earthworms Chapter 9: Arthropod natural enemies Chapter 10: Honeybees Chapter 11: Terrestrial vertebrates References PM3 Standards EPPO (2013) PM 3/22 (2) Phytophthora fragariae: inspection. EPPO Bulletin 43(3), 395– 395. Wiley Online LibraryGoogle Scholar EPPO (1989) PM 2/23 (1) Phoma exigua var. foveata. EPPO Bulletin 19(1), 157– 160. Wiley Online LibraryGoogle Scholar EPPO (2013) PM 3/24 (2) Chrysanthemum stunt viroid: inspection. EPPO Bulletin 43(3), 396– 396. Wiley Online LibraryGoogle Scholar EPPO (1991) PM 3/31 (1) Rubus viruses. Inspection and test methods. EPPO Bulletin 21(2), 241– 244. Google Scholar EPPO (1991) PM 3/36 (1) Phaeoisariopsis griseola. Inspection and test methods for bean seeds. EPPO Bulletin 21(2), 263– 264. Google Scholar EPPO (2013) PM 3/37 (2) Tilletia indica. Inspection methods for wheat seeds. EPPO Bulletin 43(3), 398– 398. Wiley Online LibraryGoogle Scholar EPPO (1994) PM 3/46 (1) Methyl bromide fumigation of citrus and other host plants to control Aleurocanthus woglumi. EPPO Bulletin 24(2), 315– 315. Wiley Online LibraryGoogle Scholar PP1 Standards EPPO (2012) PP 1/277 (1) Insecticide co-formulated mixtures. EPPO Bulletin 42(3), 353– 357. Wiley Online LibraryGoogle Scholar PP3 Standards EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products - Chapter 1: Introduction. EPPO Bulletin 23(1), 3– 17. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 2: Guidance on identifying aspects of environmental concern. EPPO Bulletin 23(1), 19– 26. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 3: Soil. EPPO Bulletin 23(1), 27– 49. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 4: Ground water. EPPO Bulletin 23(1), 51– 71. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 5: Surface water. EPPO Bulletin 23(1), 73– 98. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 6: Aquatic organisms. EPPO Bulletin 23(1), 99– 130. Wiley Online LibraryGoogle Scholar EPPO (1994) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 7: Soil microflora. EPPO Bulletin 24(1), 1– 16. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 8: Earthworms. EPPO Bulletin 23(1), 131– 149. Wiley Online LibraryGoogle Scholar EPPO (1994) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 9: Arthropod natural enemies. EPPO Bulletin 24(1), 17– 36. Wiley Online LibraryGoogle Scholar EPPO (1993) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 10: Honeybees. EPPO Bulletin 23(1), 151– 165. Wiley Online LibraryGoogle Scholar EPPO (1994) Decision-making scheme for the environmental risk assessment of plant protection products – Chapter 11: Terrestrial vertebrates. EPPO Bulletin 24(1), 37– 88. Wiley Online LibraryGoogle Scholar Volume48, Issue3December 2018Pages 538-539 ReferencesRelatedInformation

Contribution to the flora of the Maltese Islands: Euphorbia subg. Chamaesyce and Euphorbia exigua s. l. (Euphorbiaceae)

The identity and the taxonomic treatment of the species belonging to Euphorbia subg. Chamaesyce occurring on the Maltese Islands were not adequately studied both in historical and recent literature. Apart from the native sand dune species Euphorbia peplis, all records have been previously attributed to the cosmopolitan weedy species E. maculata and E. chamaesyce. This work provides the first taxonomic synopsis based on the examination of 53 specimens collected from Malta and Gozo between 2014 and 2017. The study ascertained the occurrence of six species, of which E. serpens, E. prostrata and E. hypericifolia are first reported from the Maltese Islands. Discussion on the taxonomy, origin, ecology and invasiveness of these species is provided, together with photos and an identification key. Moreover, taxonomic studies on E. exigua s. l., belonging to subg. Esula, sect. Exiguae, have been carried out on Maltese material and discussed. E. exigua var. pycnophylla, originally described as endemic of the Maltese Archipelago and recorded afterwards on the Sicilian island of Lampedusa, bears no significant morphological trait which allows to clearly distinguish it from the nominal variety. No differences in fruit and seed morphology resulted when the two varieties were compared and the slight differences present in the habit of the plant and the arrangement of leaves has been judged to be of ecotypic origin, hence justifying the lumping of this variety into the single and variable taxon E. exigua.

First Report of a Leaf Spot Caused by Boeremia exigua var. exigua on Hydrangea paniculata in Italy

Panicle hydrangea (Hydrangea paniculata) is a perennial ornamental plant belonging to the Saxifragaceae commonly used in gardens, characterized by massive upright flowers from midsummer to autumn. Starting from the end of August 2017, a previously unknown leaf spot was observed on 2- to 3-year-old plants of H. paniculata grown in borders in a garden located in Valle Cervo near Biella, northern Italy (45°36′00″N, 8°03′00″E). Ten out of 20 plants grown in this garden were affected, with 30 to 40% of leaves showing symptoms, consisting initially of circular necrotic spots, with diameter ranging between 20 and 80 mm, well defined by a brown margin. Severely infected leaves became chlorotic and abscised. The disease started from basal leaves on plants grown in shadow, at high relative humidity. In several isolations carried out from infected tissues on potato dextrose agar amended with 25 mg/liter of streptomycin sulfate a fungus was consistently isolated. After 15 days of incubation, black pycnidia, 127 to 255 μm diameter, developed, releasing hyaline, elliptical, nonseptate conidia, measuring 4.3 to 10.3 μm (average 6.9 μm) × 1.9 to 4.1 μm (average 2.7 μm). On the basis of its morphological characteristics, the fungus was identified as Phoma sp. (Boerema et al. 1976). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis of the 517 bp obtained showed 100% homology with Boeremia exigua (formerly Phoma exigua) (GenBank accession nos. MF039478, MF599109, and MF599108). The nucleotide sequence has been assigned the GenBank accession number MG766873. Because ITS analysis was not able to identify the varietas of this species, additional genes (elongation factor 1 alpha gene [EF1α] and β-tubulin [BTUB]) were amplified with primers EF1-728F/EF2 and Bt2a/Bt2b, respectively, and sequenced. BLAST analysis of the EF1α 449-bp sequence (GenBank accession no. MG970366) and the BTUB 372-bp sequence (GenBank accession no. MG970365) showed 100 and 99% similarity with the sequences of B. exigua var. exigua (GenBank accession nos. KY550228 and KR010463, respectively). Pathogenicity tests were performed by spraying leaves of healthy 24-month-old H. paniculata plants grown in pots at temperatures between 16 and 22°C with a spore and mycelial suspension (10⁶ CFU/ml). After artificial inoculation, leaves were covered with transparent plastic bags for 5 days. Plants sprayed only with sterile water served as a control. Three plants were used for each treatment. Lesions similar to those seen in naturally infected leaves developed on leaves 7 to 10 days after inoculation in all three inoculated plants, whereas control plants remained healthy. The same fungus was consistently reisolated from the lesions. The pathogenicity test was carried out twice. To our knowledge, this is the first report of B. exigua var. exigua on H. paniculata in Italy. The pathogen has been previously reported on H. macrophylla in Italy and the United States (Farr and Rossman 2017; Garibaldi et al. 2006). The disease is at present limited to a few gardens in the mountain region where it was observed.

Recombinant Promoter (MUASCsV8CP) Driven Totiviral Killer Protein 4 (KP4) Imparts Resistance Against Fungal Pathogens in Transgenic Tobacco.

Development of disease-resistant plant varieties achieved by engineering anti-microbial transgenes under the control of strong promoters can suffice the inhibition of pathogen growth and simultaneously ensure enhanced crop production. For evaluating the prospect of such strong promoters, we comprehensively characterized the full-length transcript promoter of Cassava Vein Mosaic Virus (CsVMV; -565 to +166) and identified CsVMV8 (-215 to +166) as the highest expressing fragment in both transient and transgenic assays. Further, we designed a new chimeric promoter ‘MUASCsV8CP’ through inter-molecular hybridization among the upstream activation sequence (UAS) of Mirabilis Mosaic Virus (MMV; -297 to -38) and CsVMV8, as the core promoter (CP). The MUASCsV8CP was found to be ∼2.2 and ∼2.4 times stronger than the CsVMV8 and CaMV35S promoters, respectively, while its activity was found to be equivalent to that of the CaMV35S2 promoter. Furthermore, we generated transgenic tobacco plants expressing the totiviral ‘Killer protein KP4’ (KP4) under the control of the MUASCsV8CP promoter. Recombinant KP4 was found to accumulate both in the cytoplasm and apoplast of plant cells. The agar-based killing zone assays revealed enhanced resistance of plant-derived KP4 against two deuteromycetous foliar pathogenic fungi viz. Alternaria alternata and Phoma exigua var. exigua. Also, transgenic plants expressing KP4 inhibited the growth progression of these fungi and conferred significant fungal resistance in detached-leaf and whole plant assays. Taken together, we establish the potential of engineering “in-built” fungal stress-tolerance in plants by expressing KP4 under a novel chimeric caulimoviral promoter in a transgenic approach.

Genotypic Response of Dry Bean (Phaseolus vulgaris L.) to Natural Field Infection of Ascochyta Blight (Phoma exigua var. diversispora (Bubak) Boerema) under Diverse Environmental Conditions in Rwanda

Ascochyta blight, caused by Phoma exigua var. diversispora (Bubak) Boerema, is a serious constraint in the cultivation of the common bean (Phaseolus vulgaris L.) in Rwanda, particularly in the cool and wet highland production areas. In order to identify resistant genotypes, a germplasm evaluation study was conducted to quantify the impact of the disease on phenotypic and agronomic traits under natural conditions. Field screening trials of 39 bush (Types I, II and III) and 36 climbing (Type IV) genotypes from different accessions within and outside the country were conducted at three sites, namely, Rwerere, Nyamagabe and Musanze Research Stations, for two seasons. The relative area under the disease progress curve (RAUDPC) based on evaluations of the disease severity (percentage leaf area infected), was used to evaluate the genotypes. Thirteen genotypes were identified with some level of ascochyta resistance. The study revealed Rwandan genotypes G 2333 and SMC 18 as new sources of resistance to Ascochyta blight. Additional results showed a negative relationship (r = −0.42 and −0.51 for Seasons A and B, respectively) between ascochyta infection and yield. Further relationships were identified between the plant flower colour and seed size to ascochyta resistance. Some of the identified resistant genotypes can be used to introgress ascochyta resistance into susceptible Rwandan market classes of common bean genotypes.

First Report ofBoeremia exigua var. exiguaCausing Stem and Leaf Spot on Common Speedwell in Switzerland

Common speedwell (Veronica officinalis) is grown in Switzerland for the production of herbal candies. The above-ground plant parts are harvested and dried for further use. Since 2013, a general yield decline was observed in the Emmental region, the main speedwell growing area of Switzerland. In August 2014, a survey to determine the cause was conducted in this region. In all five surveyed fields, plants with strongly reduced growth vigor were observed and from each field plant samples were taken for further investigation. On all these plants, brown necrotic lesions, with a size varying from 2-3 mm to 2 cm, and containing black pycnidia occurred on leaves and stems. After one week of incubation in a humid chamber, white spore masses were ejected from the pycnidia. The spores were translucent, biguttulate, strait to slightly curved, ellipsoid-shaped with a size of 4-7 x 1.5-3 µm and tentatively identified as a Phoma species (Sutton, 1980). The morphology and molecular phylogeny of a monospore isolate, obtai...

Interactions of arbuscular mycorrhizal and endophytic fungi improve seedling survival and growth in post-mining waste

The impact of fungal endophytes and the modulating role of arbuscular mycorrhizal fungi (AMF) on the vitality of Verbascum lychnitis, grown in the laboratory in a substratum from a post-mining waste dump was investigated. We report that inoculation with a single endophyte negatively affected the survival rate and biomass production of most of the plant-endophyte consortia examined. The introduction of arbuscular mycorrhiza fungi into this setup (dual inoculation) had a beneficial effect on both biomass yield and survivability. V. lychnitis co-inoculated with AMF and Cochliobolus sativus, Diaporthe sp., and Phoma exigua var. exigua yielded the highest biomass, exceeding the growth rate of both non-inoculated and AMF plants. AMF significantly improved the photosynthesis rates of the plant-endophyte consortia, which were negatively affected by inoculation with single endophytes. The abundance of PsbC, a photosystem II core protein previously shown to be upregulated in plants colonized by Epichloe typhina, exhibited a significant increase when the negative effect of the fungal endophyte was attenuated by AMF.

Diatom communities in thermo-mineral springs of Galicia (NW Spain)

The species composition of diatom assemblages was studied in five unpolluted thermo-mineral springs in Galicia (NW Spain). Three are considered hot and two cold, and some contain hydrogen sulphide. A total of 68 taxa (24 genera) have been recorded. The Shannon–Wiener diversity index (H′) ranged between 0.63 and 2.01. The nMDS ordination showed that diatom assemblage composition was influenced mostly by conductivity, temperature and hydrogen sulphide concentration. Diatom assemblages found in the Galician springs differed from those in springs of other geographical locations with similar physical and chemical characteristics. The most species-rich genera were Nitzschia and Achnanthidium with 10 and 8 species, respectively. Achnanthidium exiguum and Achnanthidium saprophilum had the widest distribution. Denticula thermalis and Achnanthidium caledonicum were found in environments with relatively low mineralization and low temperature, whereas Rhopalodia gibberula, Rhopalodia operculata and Fragilaria crotonensis were found in mineral-rich springs with high temperatures. Achnanthidium exiguum, A. saprophilum, Achnanthes coarctata, Achnanthes exigua var. elliptica, Mayamaea atomus, Eunotia implicata, Gomphonema minusculum, Gomphonema minutum and Cosmioneis pusilla were present in the spring with high H2S content.