First report of a phytoplasma associated with an oilseed rape disease in Greece

Oilseed rape (Brassica napus L.) is one of the most important oilseed crops in China. It is widely cultivated in China, with winter oilseed rape in Yangtze River basin and in southern China, and spring oilseed rape in northern China. In August 2017, a survey for Leptosphaeria spp. on spring oilseed rape was conducted in Minle county, Zhangye city, Gansu Province, China. The symptoms typical of blackleg on basal stems of oilseed rape were observed in the field. A large number of black fruiting bodies (pycnidia) were present on the lesions (Fig. 1A). The disease incidence of basal stem infection in the surveyed field was 19%. A total of 19 diseased stems were collected to isolate the pathogen. After surface sterilizing (75% ethanol for 30 s, 5% NaOCl for 60 s, followed by rinsing in sterilized water three times), diseased tissues were cultured on acidified potato dextrose agar (PDA) plates at 20°C for 7 days. Twelve fungal isolates were obtained. All fungal isolates produced typical tan pigment on PDA medium, and produced pycnidia after two weeks (Fig. 1B). Colony morphological characteristics indicated that these isolates might belong to Leptosphaeria biglobosa. To confirm identification, multiple PCR was conducted using the species-specific primers LmacF, LbigF, LmacR (Liu et al. 2006). Genomic DNA of each isolate was extracted using the cetyltrimethylammonium bromide (CTAB) method. DNA samples of L. maculans isolate UK-1 and L. biglobosa isolate W10 (Cai et al. 2015) were used as references. Only a 444-bp DNA band was detected in all 12 isolates and W10, whereas a 333-bp DNA band was detected only in the UK-1 isolate (Fig. 1C). PCR results suggested that these 12 isolates all belong to L. biglobosa. In addition, the internal transcribed spacer (ITS) region of these 12 isolates was analyzed for subspecies identification (Vincenot et al. 2008). Phylogenetic analysis based on ITS sequence showed that five isolates (Lb1134, Lb1136, Lb1138, Lb1139 and Lb1143) belonged to L. biglobosa ‘brassicae’ (Lbb) with 78% bootstrap support, and the other seven isolates (Lb1135, Lb1137, Lb1140, Lb1141, Lb1142, Lb1144 and Lb1145) belonged to L. biglobosa ‘canadensis’ (Lbc) with 95% bootstrap support (Fig. 1D). Two Lbb isolates (Lb1134 and Lb1136) and two Lbc isolates (Lb1142 and Lb1144) were randomly selected for pathogenicity testing on B. napus cultivar Zhongshuang No. 9 (Wang et al. 2002). Conidial suspensions (10 μL, 1 × 107 conidia mL-1) of these four isolates were inoculated on needle-wounded cotyledons (14-day-old seedling), with 10 cotyledons (20 wounded sites) per isolate. A further 10 wounded cotyledons were inoculated with water and served as controls. Seedlings were maintained in a growth chamber at 20°C with 100% relative humidity and a 12-h photoperiod. After 7 days, cotyledons inoculated with the four isolates showed necrotic lesions in the inoculated wounds. Control cotyledons had no symptoms (Fig. 2). Fungi re-isolated from the infected cotyledons showed similar colony morphology as the original isolates. Therefore, L. biglobosa ‘brassicae’ and L. biglobosa ‘canadensis’ appear to be the pathogens causing the observed blackleg symptoms on spring oilseed rape in Gansu, China. In previous studies, L. biglobosa ‘brassicae’ has been found in many crops in China, including oilseed rape (Liu et al. 2014; Cai et al. 2015), Chinese radish (Raphanus sativus) (Cai et al. 2014a), B. campestris ssp. chinensis var. purpurea (Cai et al. 2014b), broccoli (B. oleracea var. italica) (Luo et al. 2018), ornamental kale (B. oleracea var. acephala) (Zhou et al. 2019a), B. juncea var. multiceps (Zhou et al. 2019b), B. juncea var. tumida (Deng et al. 2020) and Chinese cabbage (B. rapa subsp. pekinensis) (Yu et al. 2021 accepted). To the best of our knowledge, this is the first report of L. biglobosa ‘canadensis’ causing blackleg on B. napus in China.

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First Report of Branched Broomrape (Orobanche ramosa) on Oilseed Rape (Brassica napus), Wild Mustard (Sinapis arvensis), and Wild Vetch (Vicia spp.) in Northern Greece

Plant Disease ◽

10.1094/pdis-06-11-0462 ◽

2011 ◽

Vol 95 (10) ◽

pp. 1322-1322 ◽

Cited By ~ 7

Author(s):

J. T. Tsialtas ◽

I. G. Eleftherohorinos

Keyword(s):

Brassica Napus ◽

Sea Level ◽

Oilseed Rape ◽

Parasitic Plant ◽

Yield Losses ◽

Northern Greece ◽

First Report ◽

Sinapis Arvensis ◽

Wild Mustard ◽

Orobanche Ramosa

Branched broomrape (Orobanche ramosa L.) is a chlorophyll-lacking, root parasitic plant that infects many crops and wild species (2). Plants are densely hairy with minute, glandular hairs, particularly on flowers and upper stems. Stems are erect, often branched just above the ground, and brown to straw yellow. Leaves are sparse, triangular, dark brown or purple, and arranged alternately mainly near the base of the stem. Flowers are numerous, arranged along an upright spike with a lance-shaped bract beneath the flower (about a third of the length of the flower). Petals are pale blue to purple and united into a slender tube approximately 15 mm long with two lips, the upper divided into two lobes and the lower into three lobes. The flowers have two short and two long stamens. During 2010 and 2011, a severe broomrape infection was found in an oilseed rape (Brassica napus L., cvs. Nelson and W31) crop on light-textured soil in northern Greece (Paralimnio-Serres, 41°01′N, 23°32′E, 40 m above sea level), where oriental tobacco (Nicotiana tabacum L.), a susceptible host of branched broomrape, was grown 20 years ago. The field had been cultivated with oilseed rape for three consecutive seasons in rotation with sunflower (Helianthus annuus L.). The infestation of the oilseed rape crop was confirmed in April by digging in the soil (25 to 30 cm deep) to verify attachment of the broomrape to roots of the crop plants. Density of the broomrape ranged from 20 to 120 stems per m2 and broomrape stems were 15 to 30 cm tall. Yield losses were estimated at 30 to 60%. In 2011, branched broomrape was found parasitizing wild mustard (Sinapis arvensis L.) growing as a weed in the oilseed rape field. Attachment of the broomrape was verified on a lateral root of the wild mustard plant near the soil surface, 0.95 m from the main root of the weed. Additionally, branched broomrape was found in April 2010 and 2011 parasitizing wild vetch (Vicia spp.) growing in field margins at the Cotton and Industrial Plants Institute-National Agricultural Research Foundation (Sindos, 40°41′N, 22°48′E, 17 m above sea level). The parasitized vetch plants were growing on light-textured soil. Attachment of the broomrape to roots of the host plants was verified at a 5-cm soil depth. Stems of the parasite were short (7 to 10 cm). The monthly mean air temperature for February (7.3°C), March (9.6°C), and April (14.1°C) and mean soil temperature at a 10-cm depth for February (7.0°C), March (9.5°C), and April (13.4°C), before verification of the broomrape infestation at Sindos, were much lower than the temperature range reported (18 to 23°C) for branched broomrape infestations (1). To our knowledge, this is the first report of O. ramosa on oilseed rape, wild mustard, and wild vetch in northern Greece. Since branched broomrape could be a significant parasite for oilseed rape, which was introduced to Greece as a commercial crop 5 years ago, measures should be taken to avoid significant yield losses from this parasitic plant. References: (1) I. Faithfull and D. McLaren. Landcare Note LC0272. Department of Sustainability and Environment, State of Victoria, Melbourne, Australia, 2004. (2) C. Parker. Pest Manag. Sci. 65:453, 2009.

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First Report of White Leaf Spot Caused by Pseudocercosporella capsellae on Brassica juncea in Australia

Plant Disease ◽

10.1094/pd-89-1131b ◽

2005 ◽

Vol 89 (10) ◽

pp. 1131-1131 ◽

Cited By ~ 9

Author(s):

L. Eshraghi ◽

M. P. You ◽

M. J. Barbetti

Keyword(s):

Brassica Juncea ◽

Oilseed Rape ◽

Western Australia ◽

Leaf Spot ◽

Oilseed Crop ◽

Single Spore ◽

First Report ◽

White Leaf ◽

Humidity Chamber ◽

Stem Lesions

Brassica juncea (L.) Czern & Coss (mustard) has potential as a more drought-tolerant oilseed crop than the Brassica napus, and the first two canola-quality B. juncea cultivars will be sown as large strip trials across Australia in 2005. This will allow commercial evaluation of oil and meal quality and for seed multiplication for the commercial release Australia-wide in 2006. Inspection of experimental B. juncea field plantings at Beverley (32°6′30″S, 116°55′22″E), and Wongan Hills (30°50′32″S, 116°43′33″E), Western Australia in September 2004 indicated the occurrence of extensive leaf spotting during B. juncea flowering. Symptoms of this disease included as many as 15 or more grayish white-to-brownish spot lesions per leaf, often with a distinct brown margin. Some elongate grayish stem lesions were also observed as reported earlier for B. napus oilseed rape (1). When affected materials were incubated in moist chambers for 48 h, abundant conidia typical of Pseudocercosporella capsellae (Ellis & Everh.) Deighton were observed that matched the descriptions of conidia given by Deighton (2) and those on B. napus in Western Australia (1). Five single-spore cultures from lesions were grown on water agar (WA) where the colonies characteristically produced purple-pink pigment in the agar after 2 weeks growth in an incubator maintained at 20°C with a 12-h photoperiod (3). Since agar cultures of P. capsellae rarely produce conidia (3), this observation helped with the verification of the cultures. Mycelial inoculum from these cultures was used to inoculate cotyledons of 50 7-day-old plants of B. juncea to satisfy Koch's postulates. Small pieces of mycelia were teased out from the surface of the growing margin of potato dextrose agar (PDA) cultures and inoculated onto both lobes of each cotyledon and plants incubated in a 100% humidity chamber for 48 h within a controlled environment room maintained at 20/15°C (day/night) with a 12-h photoperiod. After 2 weeks, lesions 5 to 8 mm in diameter were observed on the cotyledons. There were no symptoms on control plants that were treated with water only. Lesions on infected cotyledons incubated on moist filter paper for 24 h produced abundant cylindrical conidia showing 2 to 3 septa measuring 42.9 to 71.4 μm long and 2.9 to 3.1 μm wide. Single-spore isolations from these conidia produced typical P. capsellae colonies showing purple-pink pigments in WA, and dark, compacted, and slow-growing colonies with a dentate margin on PDA. White leaf spot caused by P. capsellae is an important disease of crucifers worldwide, but to our knowledge, this is the first report of P. capsellae on B. juncea in Australia. In Western Australia, P. capsellae occurs on B. napus oilseed rape (1) and in 1956, 1984, and 1987, it was recorded on B. rapa, B. oleracea, and B. chinensis, respectively (4), and on the same range of Brassica hosts in other regions of Australia. References: (1) M. J. Barbetti and K. Sivasithamparam. Aust. Plant Pathol.10:43, 1981. (2) F. C. Deighton. Commonw. Mycol. Inst. Mycol. Pap. 133:42, 1973. (3) S. T. Koike. Plant Dis. 80:960, 1996. (4) R. G. Shivas. J. R. Soc. West. Aust. 72:1, 1989.

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The number of generations of Heterodera schachtii completed on oilseed rape (Brassica napus L.) during the UK growing season

Nematology ◽

10.1163/15685411-00002889 ◽

2015 ◽

Vol 17 (5) ◽

pp. 557-565 ◽

Cited By ~ 1

Author(s):

Stephen Kakaire ◽

Ivan G. Grove ◽

Patrick P.J. Haydock

Keyword(s):

Brassica Napus ◽

Plant Growth ◽

Oilseed Rape ◽

Growing Season ◽

Heterodera Schachtii ◽

Brassica Napus L ◽

First Report ◽

Two Generations ◽

Growth Differences ◽

The Uk

The number of generations completed by a UK field population of Heterodera schachtii on winter and spring oilseed rape (OSR; Brassica napus L.) during the growing season of 2010/2011 was investigated. The experiments were conducted in pots outdoor using UK OSR winter cultivars (cvs) Flash and Castille and spring cvs Belinda and Heros. The results indicated that temperature was crucial in determining the number of generations completed on OSR during the growing season. At least one generation was completed on cv. Castille, whilst two generations were completed on cvs Flash, Belinda and Heros during the growing season. Development of H. schachtii was faster on hybrid OSR cvs Flash and Belinda, suggesting that the hybrids were better hosts of H. schachtii than the conventional cvs Castille and Heros. Cultivar Flash was more susceptible to H. schachtii infection than cv. Castille, while cv. Belinda was more susceptible than cv. Heros. However, no major plant growth differences were observed between the cvs investigated. This is the first report on the number of generations of H. schachtii completed on current cultivars of OSR in the UK.

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Pythium polymastum pathogenic on oilseed rape and other crucifers

Canadian Journal of Botany ◽

10.1139/b74-154 ◽

1974 ◽

Vol 52 (6) ◽

pp. 1205-1208 ◽

Cited By ~ 4

Author(s):

T. C. Vanterpool

Keyword(s):

Oilseed Rape ◽

Root Rot ◽

Brassica Campestris ◽

Cultivated Plants ◽

Field Soil ◽

Alternative Hosts ◽

First Report

Pythium polymastum has been found in the roots of oilseed rape (Brassica campestris and B. napus), Capsella bursa-pastoris, and Lunaria annua, grown in field soil from widely separated localities in Saskatchewan. It is virulent on rape and 18 other crucifers, and avirulent or only slightly virulent on numerous cultivated plants belonging to other families. This is the first report of the fungus as a pathogen on crucifers. It is suggested that it may play a part in a root-rot complex, that it is indigenous, and that cruciferous weeds act as alternative hosts.

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First Report of ‘Candidatus Phytoplasma asteris’ Associated with Oilseed Rape Phyllody in Poland

Plant Disease ◽

10.1094/pdis-03-11-0177 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1475-1475 ◽

Cited By ~ 6

Author(s):

A. Zwolińska ◽

K. Krawczyk ◽

T. Klejdysz ◽

H. Pospieszny

Keyword(s):

Oilseed Rape ◽

Animal Feed ◽

Disease Incidence ◽

Polymorphism Analysis ◽

Winter Oilseed Rape ◽

Aster Yellows ◽

First Report ◽

Rdna Sequences ◽

Pcr Products ◽

Phytoplasma Infection

Winter oilseed rape (Brassica napus L.) is widely grown in Poland to produce vegetable oil for industrial processing of human and animal feed. In recent years, according to European Union directives on the use of biofuels (Directive 2003/30/EC), the area under oilseed rape cultivation in Poland has dramatically increased to 810,000 ha in 2009 and is still increasing. Morphological deformations of winter oilseed rape indicative of phytoplasma infection have been observed sporadically in Poland since 2000 (3). Plants exhibiting floral virescence, phyllody, as well as auxiliary bud proliferation, reduced leaves, and malformation of siliques were identified during surveys of research fields in Wielkopolska during May and June of 2009 and 2010. To confirm phytoplasma infection of these plants, inflorescence and leaf tissues were collected from nine diseased and three symptomless plants from three different field locations with 1 to 16% disease incidence. Total DNA was extracted from each plant tissue sample with a modified cetyltrimethylammoniumbromide method (2). Samples were analyzed for phytoplasma DNA with a nested PCR assay employing phytoplasma universal rRNA operon primer pair P1/P7 followed by R16F2n/R16R2, using previously described conditions (1). PCR products of 1.8 and 1.2 kb were obtained from all diseased plants only following PCRs with P1/P7 and nested primer pair R16F2n/R16R2, respectively. PCR products were not obtained from symptomless plants. Eight 1.2-kb amplicons were sequenced (GenBank Accession Nos. JN193475 to JN193482). Comparative analysis of the R16F2n/R16R2 rDNA sequences confirmed the phytoplasma origin of the rDNA sequences that shared 100 to 99% identity with Maize bushy stunt phytoplasma (GenBank Accession No. HQ530152), Alfalfa stunt phytoplasma (GenBank Accession No. GU289675), Primula green yellows phytoplasma (GenBank Accession No. HM590623), and other aster yellows group phytoplasmas. A 1.8-kb amplicon of isolate designated RzW14 was sequenced (GenBank Accession No. HM561990) and had 99% identity with Aster yellow group phytoplasmas from Lithuania (GenBank Accession Nos.GU223208 and AY744071). A virtual restriction fragment length polymorphism analysis of the 16S rDNA sequences from the R16F2n/R16R2 amplicons was performed with iPhyClassifier (4). Restriction profile comparisons identified all aster yellows group phytoplasmas as subgroup 16SrI-B strains. To our knowledge, this is the first report of a ‘Candidatus Phytoplasma asteris’-related strain infecting oilseed rape in Poland. References: (1) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) A. C. Padovan et al. Aust. J. Grape Wine Res. 1:25, 1995. (3) M. Starzycki and E. Starzycka. Oilseed Crops 21:399, 2000. (4) Y. Zhao et al. Int. J. Syst. Evol. Microbiol. 59:2582, 2009.

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First Report of Oilseed Rape Stem Rot Caused by Sclerotinia sclerotiorum in Greece

Plant Disease ◽

10.1094/pdis-92-10-1473c ◽

2008 ◽

Vol 92 (10) ◽

pp. 1473-1473 ◽

Cited By ~ 1

Author(s):

G. T. Tziros ◽

G. A. Bardas ◽

J. T. Tsialtas ◽

G. S. Karaoglanidis

Keyword(s):

Oilseed Rape ◽

Sclerotinia Sclerotiorum ◽

Morphological Characteristics ◽

The United States ◽

Stem Rot ◽

Sclerotinia Stem Rot ◽

Brassica Napus L ◽

First Report ◽

Plastic Bag ◽

Pathogenicity Tests

Oilseed rape (Brassica napus L.) was recently introduced into Greece for the production of biofuels. During May of 2007, symptoms typical of stem rot were observed on oilseed rape plants in three commercial fields in the area of Galatades-Pella, Central Macedonia, Greece. Approximately 30% of the plants were affected. Symptoms began as a chlorotic wilt on the foliage and developed into necrosis of basal stems. In the advanced stages of the disease, stems and branches became bleached and eventually died. White, as well as black, mycelium and irregularly shaped sclerotia (2 to 5 mm in diameter) were produced abundantly on and inside the affected stems. To isolate the pathogen, 20 symptomatic 6-month-old plants were collected from each field. Sclerotia were dipped in 70% ethanol, surface sterilized in 1% sodium hypochlorite for 1 min, and rinsed in sterile water. Sclerotia placed on potato dextrose agar (PDA) were incubated in the dark at 25°C for 10 days. Sclerotinia sclerotiorum (Lib.) de Bary was identified on the basis of morphological characteristics (2). To conduct pathogenicity tests, 10 6-week-old oilseed rape plants (cv. Titan) were each inoculated with a 5-mm-diameter colonized PDA disk placed in wounds made in the basal stem with a sterile scalpel. Five control plants were treated similarly except that the agar disk did not contain mycelium. Plants were then covered with a plastic bag to maintain high humidity. After 72 h, the bags were removed and the plants were maintained in a growth chamber at 23 to 25°C with a 12-h photoperiod and 75% relative humidity. Pathogenicity tests were repeated three times. Symptoms identical to those observed in the field developed within 12 days after inoculation; control plants remained healthy. The fungus was reisolated from all inoculated plants, confirming Koch's postulates. S. sclerotiorum has been reported on oilseed rape in Argentina, Australia, Brazil, Canada, the United States, and New Zealand (1). To our knowledge, this is the first report of Sclerotinia stem rot of oilseed rape in Greece. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2008. (2) L. M. Kohn. Phytopathology 69:881, 1979.

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First Report of Dimethachlon Resistance in Field Isolates of Sclerotinia sclerotiorum on Oilseed Rape in Shaanxi Province of Northwestern China

Plant Disease ◽

10.1094/pdis-07-13-0730-pdn ◽

2014 ◽

Vol 98 (4) ◽

pp. 568-568 ◽

Cited By ~ 15

Author(s):

F. Zhou ◽

F. X. Zhu ◽

X. L. Zhang ◽

A. S. Zhang

Keyword(s):

Oilseed Rape ◽

Sclerotinia Sclerotiorum ◽

The United States ◽

Northwestern China ◽

Shaanxi Province ◽

Resistant Isolate ◽

Economic Losses ◽

First Report ◽

Field Isolates ◽

Wide Range

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen causing diseases in a wide range of plants, including oilseed rape (3). Substantial economic losses caused by S. sclerotiorum have been reported in the United States, Canada, Brazil, South Africa, Hungary, India, Nepal, and Japan (1). Application of fungicides is the principal tool for controlling S. sclerotiorum because of lack of high level of host resistance. Dicarboximide fungicides such as dimethachlon have been widely used to control S. sclerotiorum in recent years in China and field isolates with reduced sensitivity to dimethachlon have been reported in Jiangsu Province of eastern China (2). In order to understand the current status of dimethachlon resistance in S. sclerotiorum isolates of northwestern China, 196 and 344 isolates of S. sclerotiorum collected from oilseed rape fields in 10 counties throughout Shaanxi Province in 2011 and 2012, respectively, were assayed for sensitivity to dimethachlon using 5 μg ml–1 dimethachlon as a discriminatory dose. Mycelial plugs (6 mm in diameter) cut from the margin of a 48-h-old colony were placed in the center of petri dishes containing potato dextrose agar (PDA) amended with 5 μg ml–1 dimethachlon; PDA without fungicide served as the control. Cultures were incubated at 26°C and colony growth was measured after 72 h of incubation. Isolates that showed growth on PDA amended with fungicide were tentatively considered resistant to dimethachlon, whereas the completely inhibited isolates were considered sensitive. Results showed that 1.02% or 2 isolates of the 196 isolates collected in 2011 and 3.78% or 13 isolates of the 344 isolates collected in 2012 were resistant to dimethachlon. For all the isolates considered resistant and 42 randomly selected sensitive isolates, 50% effective concentrations (EC50) were determined on PDA amended with a series of dimethachlon concentrations. The average EC50 value of dimethachlon for sensitive isolates was 0.29 ± 0.02 μg ml–1 Resistance ratios (EC50 of resistant isolate / average EC50 of sensitive isolates) for the two resistant isolates detected in 2011 were 10.28 and 23.83, respectively, whereas resistance ratios for the 13 resistant isolates detected in 2012 ranged from 24.90 to 101.97. The average EC50 value of dimethachlon for the 13 resistant isolates detected in 2012 was 19.05 μg ml–1, and EC50 values for the two resistant isolates detected in 2011 were 2.98 and 6.91 μg ml–1, respectively. These results indicated that both resistance frequency and resistance level increased from 2011 to 2012. Bioassay results of three resistant isolates indicated that there was positive cross-resistance between dimethachlon and other dicarboximide fungicides such as iprodione and procymidone. To our knowledge, this is the first report of dimethachlon resistance in S. sclerotiorum in Shaanxi Province of northwestern China. The molecular mechanism of dimethachlon resistance in field isolates of S. sclerotiorum remains to be studied. Although resistance frequency is low at present, dimethachlon resistance should be kept in mind and fungicide resistance management tactics such as use of biological control agents, fungicide tank-mixing, or alternating dimethachlon with other fungicides having different modes of action is recommended in controlling S. sclerotiorum. References: (1) M. D. Bolton et al. Mol Plant Pathol. 7:1, 2006. (2) H. X. Ma et al. Plant Dis. 93:36, 2009. (3) L. H. Prudy. Phytopathology 69:875, 1979.

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