Re-consideration of Peronospora farinosa infecting Spinacia oleracea as distinct species, Peronospora effusa

Downy mildew is probably the most widespread and potentially destructive global disease of spinach (Spinacia oleracea). The causal agent of downy mildew disease on various plants of Chenopodiaceae, including spinach, is regarded as a single species, Peronospora farinosa. In the present study, the ITS rDNA sequence and morphological data demonstrated that P. farinosa from S. oleracea is distinct from downy mildew of other chenopodiaceous hosts. Fifty-eight spinach specimens were collected or loaned from 17 countries of Asia, Europe, Oceania, North and South America, which all formed a distinct monophyletic group. No intercontinental genetic variation of the ITS rDNA within Peronospora accessions causing spinach downy mildew disease was found. Phylogenetic trees supported recognition of Peronospora from spinach as a separate species. Microscopic examination also revealed morphological differences between Peronospora specimens from Spinacia and P. farinosa s. lat. specimens from Atriplex, Bassia, Beta, and Chenopodium. Consequently, the name Peronospora effusa should be reinstated for the downy mildew fungus found on spinach. Here, a specimen of the original collections of Peronospora effusa is designated as lectotype.     

Identity of the downy mildew pathogens of basil, coleus, and sage with implications for quarantine measures

The downy mildew pathogen of basil (Ocimum spp.) has caused considerable damage throughout the past five years, and an end to the epidemics is not in sight. The downy mildew of coleus (Solenostemon spp.) is just emerging and here we report that it was very recently introduced into Germany. Although it has been recognised that these pathogens are a major threat, the identity of the pathogens is still unresolved, and so it is difficult to devise quarantine measures against them. Using morphological comparison and molecular phylogenetic reconstructions we confirmed in this study that the downy mildews of basil and coleus are unrelated to Peronospora lamii, which is a common pathogen of the weed Lamium purpureum. In addition, we conclude by the investigation of the type specimen of P. swingleii and downy mildew specimens on Salvia officinalis that the newly occurring pathogens are not identical to P. swingleii on Salvia reflexa. The taxonomy of the downy mildew pathogens of hosts from the Lamiaceae and, in particular, from the tribes Mentheae and Elsholtzieae, is discussed, and a new species is described to accommodate the downy mildew pathogen of basil and coleus, which is the first downy mildew pathogen known to be parasitic to hosts of the tribe Ocimeae.     

Morphological and Molecular Characterization of the Causal Agent of Downy Mildew on Quinoa (<Emphasis Type="Italic">Chenopodium quinoa</Emphasis>)

Downy mildew is an economically important and widespread disease in quinoa (Chenopodium quinoa) growing areas. Although in many studies Peronospora farinosa is most commonly regarded as the causal agent of the disease, identification and classification of the pathogen remain still uncertain due to its taxonomic confusion. Thirty-six Peronospora isolates from quinoa with different geographic origins including Argentina, Bolivia, Denmark, Ecuador, and Peru were morphologically and molecularly compared with Peronospora species from other Chenopodium species. The morphology of three herbarium specimens was similar to that of P. variabilis, which originated from C. album, characterized by flexuous to curved ultimate branchlets and pedicellated conidia. Phylogenetic analysis based on ITS rDNA sequences also placed the quinoa pathogen within the same clade as P. variabilis. Within the ITS rDNA sequences of the quinoa pathogens, two base substitutions were found, which separated the majority of the Danish isolates from isolates from South America, but no sequence difference was found among the isolates from different cultivars of quinoa. The present results indicate that the pathogen responsible for the quinoa downy mildew is identical to Peronospora variabilis and that it should not be lumped with P. farinosa as claimed previously by most studies.     

Bird pollination in South African Salvia species

Approximately one-fourth of the more than 900 world-wide distributed Salvia species (Lamiaceae) is ornithophilous. With few exceptions they occur in the New World, being predominantly pollinated by hummingbirds. In the Old World only Salvia africana-lutea and the recently described Salvia thermarum, both from the Cape Province of South Africa, were observed to be pollinated by sunbirds and white-eyes. Among the 23 South African Salvia species Salvia lanceolata is a further candidate for being bird pollinated. For the first time we describe and illustrate its pollination by Nectarinia chalybea and Zosterops pallidus. We compare the ornithophilous syndrome of the three mentioned Salvia species and relate them to the morphological fitting of the most common nectarivorous birds of the Southwestern Cape (Cape peninsula to Worcester). We conclude that each of the birds could act as a pollinator and that the three co-occurring Salvia species are not mechanically isolated from each other. The degree of specialisation towards bird pollination, possible hybridisation events and evolution of bird pollination in South African Salvia species are discussed.     

Morphological and molecular analyses support the existence of host-specific Peronospora species infecting Chenopodium

About 20 species of Peronospora have been reported to cause downy mildew on Chenopodium, but, particularly in plant pathology literature, only one species, P. farinosa, is considered to be involved. We performed sequence analysis of the ITS rDNA to reveal the phylogenetic relationships of Peronospora specimens from five species of Chenopodium, viz. C. album, C. ambrosioides, C. bonus-henricus, C. hybridum, and C. polyspermum. The five clades corresponded to particular Chenopodium species, and showed a high level of sequence divergence. Differences in the morphology of the conidia and ultimate branchlets also supported the separation of the five groups at the host species level. These results suggest that the names P. variabilis, P. boni-henrici, P. chenopodii, and P. chenopodii-polyspermi should be used for the four downy mildew pathogens specific to C. album, C. bonus-henricus, C. hybridum, and C. polyspermum, respectively. The Peronospora on C. ambrosioides was found to be an independent species.     

Diversity and species boundaries in floricolous downy mildews

Floricolous downy mildews are a monophyletic group of members of the genus Peronospora (Oomycota, Peronosporales). These downy mildews can be found on a variety of families of the Asteridae, including Asteraceae, Campanulaceae, Dipsacaceae, Lamiaceae, and Orobanchaceae. With the exception of Peronospora radii, which can also cause economically relevant losses, sporulation usually takes place only on floral parts of their hosts. However, only very few specimens of these mostly inconspicuous downy mildews have so far been included in molecular phylogenies. Focusing on Lamiaceae, we have investigated multiple specimens of floricolous downy mildews for elucidating species boundaries and host specificity in this group. Based on both mitochondrial and nuclear loci, it became apparent that phylogenetic lineages in the Lamiaceae seem to be host genus specific and significant sequence diversity could be found between lineages. Based on distinctiveness in both phylogenetic reconstructions and morphology, the downy mildew on flowers of Stachys palustris is introduced as a new species, Peronospora jagei sp. nov., which can be morphologically distinguished from Peronospora stigmaticola by broader and shorter conidiospores. The diversity of the floricolous down mildews might be higher than previously assumed, although specimens from a much broader set of samples will be needed to confirm this view.     

Reclassification of Two <Emphasis Type="Italic">Peronospora</Emphasis> Species Parasitic on <Emphasis Type="Italic">Draba</Emphasis> in <Emphasis Type="Italic">Hyaloperonospora</Emphasis> Based on Morphological and Molecular Phylogenetic Data

On the family Brassicaceae, the causal agent responsible for downy mildew disease was originally regarded as a single species, Peronospora parasitica (now under Hyaloperonospora), but it was recently reconsidered to consist of many distinct species. In this study, 11 specimens of Peronospora drabae and P. norvegica parasitic on the genus Draba were investigated morphologically and molecularly. Pronounced differences in conidial sizes (P. drabae: 14–20 × 12.5–15.5 μm; P. norvegica: 20–29 × 15.5–22 μm) and 7.8% sequence distance between their ITS1-5.8S-ITS2 rDNA sequences confirmed their status as distinct species. Based on ITS phylogeny and morphology (monopodially branching conidiophores, flexuous to sigmoid ultimate branchlets, hyaline conidia and lobate haustoria), the two species unequivocally belong to the genus Hyaloperonospora and not to Peronospora to which they were previously assigned. Therefore, two new combinations, Hyaloperonospora drabae and H. norvegica, are proposed. The two taxa are illustrated and compared using the type specimen for H. norvegica and authentic specimens for H. drabae, which is lectotypified.     

南美蟛蜞菊霜霉病病原鉴定及系统发育分析

[目的]为从天敌病原生物方面探索外来入侵植物南美蟛蜞菊的生物防治,对新发现的南美蟛蜞菊霜霉病进行病原鉴定和系统发育分析。[方法]在广东省广州市对南美蟛蜞菊霜霉病的发生及危害情况进行调查,并通过病害症状识别、病原显微形态记录与比较、病原菌及其近似种ITS序列结构比较、LSU序列和ITS序列系统发育分析,对南美蟛蜞菊霜霉病病原进行鉴定和系统发育分析。[结果]南美蟛蜞菊霜霉病在广州零星发生,但该病害在华南农业大学校园内发生较严重,发病率达50%~70%,病情指数为30~35。经鉴定,其病原菌为南美蟛蜞菊单轴霉,是国内一新记录种。基于病原菌LSU序列和ITS序列的系统发育分析显示,侵染菊科植物的单轴霉属菌种聚在一个分枝,亲缘关系密切,与侵染其他不同科寄主植物的单轴霉亲缘关系较远。ITS序列结构比较显示,寄生于菊科向日葵族植物的单轴霉属菌种的ITS2区包含多个重复序列,不同菌种间的ITS2区重复序列相似度不同,说明侵染菊科向日葵簇植物的单轴霉属菌物可细分成多个种,而不是只有向日葵单轴霉。[结论]广州发生的南美蟛蜞菊霜霉病是该寄主上首次正式报道的病害,鉴定的病原菌也是国内一新记录种;寄生在菊科植物上的单轴霉属种类不尽相同,但亲缘关系紧密。     

A revision of Salvia sect. Ekmania (Lamiaceae)

A taxonomic treatment ofSalvia sect.Ekmania, a group of tall shrubs endemic to the Caribbean island of Hispaniola, is provided. Morphology, phenology, pollination biology, habitats, and distributions are discussed. Species boundaries are examined using phenetic analysis of morphological data. Eight species are here accepted as belonging to the section. Two recently described species,S. lavendula andS. paryskii, are considered for inclusion in the section, but only the latter appears to be a member.Salvia lachnaiclada andS. ottoschulzii are treated as conspecific.Salvia bahorucona is recognized as a distinct species.     

Speciation process of <Emphasis Type="Italic">Salvia isensis</Emphasis> (Lamiaceae), a species endemic to serpentine areas in the Ise-Tokai district,Japan, from the viewpoint of the contradictory phylogenetic trees generated from chloroplast and nuclear DNA

To understand the speciation process of Salvia isensis (Lamiaceae), a species endemic to a special environment (serpentine areas in the Ise-Tokai district, central Honshu, Japan), chloroplast DNA (cpDNA) and nuclear ribosomal DNA (nrDNA) were employed to analyze the phylogenetic relationships of S. isensis with related species in Japan. Allozymic polymorphisms were also used to analyze genetic relationships among Salvia species. A contradiction in the phylogenetic positions of species studied was detected when phylogenetic trees were constructed using cpDNA or nrDNA, i.e., S. isensis was a sister to the other species in phylogenetic trees generated from cpDNA, while S. japonica was a sister to the other species in the case of nrDNA. Genetic relationships between Salvia species estimated from allozymic polymorphisms did not contradict to the topology for nrDNA. Using the present results, the speciation process of S. isensis is discussed with regard to introgressive gene exchanges between related species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genotyping by sequencing suggests overwintering of Peronospora destructor in southwestern Québec,Canada

Several Peronospora species are carried by wind over short and long distances, from warmer climates where they survive on living plants to cooler climates. In eastern Canada, this annual flow of sporangia was thought to be the main source of Peronospora destructor responsible for onion downy mildew. However, the results of a recent study showed that the increasing frequency of onion downy mildew epidemics in eastern Canada is associated with warmer autumns, milder winters, and previous year disease severity, suggesting overwintering of the inoculum in an area where the pathogen is not known to be endogenous. In this study, genotyping by sequencing was used to investigate the population structure of P. destructor at the landscape scale. The study focused on a particular region of southwestern Québec—Les Jardins de Napierville—to determine if the populations were clonal and regionally differentiated. The data were characterized by a high level of linkage disequilibrium, characteristic of clonal organisms. Consequently, the null hypothesis of random mating was rejected when tested on predefined or nonpredefined populations, indicating that linkage disequilibrium was not a function of population structure and suggesting a mixed reproduction mode. Discriminant analysis of principal components performed with predefined population assignment allowed grouping P. destructor isolates by geographical regions, while analysis of molecular variance confirmed that this genetic differentiation was significant at the regional level. Without using a priori population assignment, isolates were clustered into four genetic clusters. These results represent a baseline estimate of the genetic diversity and population structure of P. destructor.     

Comparison of Chemical Profile and Antioxidant Capacity of Seeds and Oils from Salvia sclarea and Salvia officinalis

Composition of tocopherols, tocotrienols, carotenoids, fatty acids, as well as hydrophilic and lipophilic antioxidant activities, were determined in seeds of two Salvia species and oils obtained from them. Both seeds contained a large amount of oil (around 20%) rich in polyunsaturated fatty acids. While Salvia officinalis seed oil can be classified as oleic‐linoleic oil, the predominant fatty acid in Salvia sclarea was α‐linolenic acid (around 54%). Among tocols, the main isomers in both seeds and oils were γ‐tocopherol, followed by α‐tocopherol. Concerning carotenoids, their concentration was around 0.75 mg/100 g of seeds and 0.16 mg/100 g of oils, with a predominance of lutein. Oil and seeds of S. officinalis exhibited higher antioxidant potential compared to S. sclarea investigated samples which could be attributed to higher content of total vitamin E and carotenoids. This study provides results that enables use of two Salvia species as new alternative sources of vegetable oils.     

Sources of resistance to downy mildew (<Emphasis Type="Italic">Peronospora parasitica</Emphasis> (Pers. (ex Fr.) Fr.) in Sicilian germplasm of cauliflower and broccoli

Downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) is a serious disease of brassicas in several countries. Seedlings are very susceptible to this pathogen and crops require frequent fungicide treatments to reach a good marketable yield. The use of resistant cultivars can be the most economical, reliable and environmental friendly method for managing this disease. In this work 32 Sicilian landraces and 16 commercial cultivars of cauliflower and broccoli (B. oleracea) were screened for downy mildew resistance at the cotyledon stage using one P. parasitica strain from Portugal and one from Sicily (Italy). Seven-day old seedlings were inoculated by deposing a droplet of a spore suspension on the cotyledons, incubated under controlled environment and scored 7 days later using a seven-class scale of interaction phenotype (IP), which took into consideration host response and pathogen sporulation. There were no differences in virulence between the two P. parasitica isolates. Accessions ranged from very susceptible to highly resistant to downy mildew showing a variable number of resistant individuals per accession. Forty accessions were very susceptible to downy mildew and are of no interest as sources of resistance, since most of the seedlings were scored in the most susceptible IP classes. Seven accessions had intermediate resistance and included individuals that expressed some degree of resistance. Accession Cv 90 (Cavolfiore Torino) and Br 63 (Sparaceddu) showed the majority of seedlings in the resistant IP classes and may constitute valuable sources of resistance to downy mildew to be used in breeding programs.     

钟冠报春苣苔(苦苣苔科)的分类鉴定

原唇柱苣苔属(Chirita Buch.-Ham. ex D. Don)为一个人为界定的属, 2011年在分子系统学研究的基础上对该属及其近缘属开展了系统发育重建工作,其中绝大部分的原唇柱苣苔属唇柱苣苔组(Sect. Gibbosaccus C. B. Clark)的物种被并入了广义报春苣苔属(Primulina Hance)。然而,由于历史原因和早期经典分类学在研究方法上的局限性以及对现报春苣苔属部分物种的营养器官与生殖器官的认知不够,该属下一些物种的分类仍存在一些问题,亟待深入研究。比如,在对中国和越南分布的苦苣苔科植物开展研究的过程中,作者发现两个报春苣苔属的物种——广布于中国西南和华南直至中南半岛中部的钟冠报春苣苔[Primulina swinglei(Merr.)Mich. Möller & A. Weber]命名人和原被认为是中国与广西特有种的疏花报春苣苔[P. laxiflora(W. T. Wang)Yin. Z. Wang]之间的鉴定存在分类学问题,需要进一步厘清两者之间的关系。该文对这两个物种进行了形态比较,同时通过对这两种植物的原始描述对比、植物标本检查、栽培观察以及野外实地观察,确定疏花报春苣苔是钟冠报春苣苔的异名。此外,还明确了钟冠报春苣苔的后选指定模式标本。     

Development of transgenic pearl millet (Pennisetum glaucum (L.) R. Br.) plants resistant to downy mildew

Transgenic pearl millet lines expressing pin gene—exhibiting high resistance to downy mildew pathogen, Sclerospora graminicola—were produced using particle-inflow-gun (PIG) method. Shoot-tip-derived embryogenic calli were co-bombarded with plasmids containing pin and bar genes driven by CaMV 35S promoter. Bombarded calli were cultured on MS medium with phosphinothricin as a selection agent. Primary transformants 1T₀, 2T₀, and 3T₀ showed the presence of both bar and pin coding sequences as evidenced by PCR and Southern blot analysis, respectively. T₁ progenies of three primary transformants, when evaluated for downy mildew resistance, segregated into resistant and susceptible phenotypes. T₁ plants resistant to downy mildew invariably exhibited tolerance to Basta suggesting co-segregation of pin and bar genes. Further, the downy mildew resistant 1T₁ plants were found positive for pin gene in Southern and Northern analyses thereby confirming stable integration, expression, and transmission of pin gene. 1T₂ progenies of 1T₀ conformed to dihybrid segregation of 15 resistant:1 susceptible plants.     

Effect of the environmental conditions on essential oil profile in two Dinaric Salvia species: S. brachyodon Vandas and S. officinalis L.

Two species belonging to the genus Salvia (Salvia brachyodon Vandas and Salvia officinalis L.) from Dalmatian region were studied for their essential oil composition, genome size and base composition. These species showed the same chromosome number (2n = 14), similar genome size (0.95 and 0.97 pg/2C) and base composition (38.52 and 38.55 GC%), respectively. This is the first estimation of DNA content and base composition for both species.     

高山物种栗色鼠尾草(Salvia castanea Diels)访花昆虫多样性与传粉行为变化

唇形科鼠尾草属是世界性分布、物种多样性丰富的大类群,具有独特的传粉模式和多样化的生态类型及繁殖策略,以往对鼠尾草属的花结构和雄蕊杠杆的生态功能、雄蕊杠杆机制对传粉者空间变异的进化响应和表型选择等方面已有较深入的研究,但至今对分布于不同区系代表性物种的传粉者组成、访花行为和繁育系统特征仍知之甚少。对分布于喜马拉雅东段至横断山高海拔地区栗色鼠尾草的传粉生态、交配系统和繁殖特性进行了研究,分析了2014年至2016年的年际间、2014年晴天和阴雨天的传粉者组成和传粉行为变化,探讨了这些变化对繁殖成功的影响。研究结果表明：3年共发现栗色鼠尾草有9种访花昆虫,传粉者组成及其行为变化较为明显。2014年有桔尾熊蜂Bombus friseanus、灰熊蜂B.grahami、圣熊蜂B.religiosus和中华蜜蜂Apis cerana 4种有效传昆虫,2015年仅有桔尾熊蜂是有效传粉者,而2016年的有效传粉昆虫改变为灰熊蜂和圣熊蜂。栗色鼠尾草的盗蜜现象较为普遍,主要盗蜜昆虫为灰熊蜂和桔尾熊蜂。桔尾熊蜂访花行为的年际变化较大,受天气条件的影响明显,同时其有效传粉行为可能显著影响了灰熊蜂的盗蜜行为。栗色鼠尾草的繁育系统为专性异交,主要依靠传粉者进行授粉,缺少传粉者时低程度的主动自花授粉可为其提供繁殖保障,且没有花粉限制和近交衰退。研究揭示了在高海拔地区,多变的天气条件可能显著影响着鼠尾草属植物的传粉者种类组成、访花行为和传粉效率,进而影响植物的繁殖成效和种群稳定。有效传粉频率是保证栗色鼠尾草较高自然结实率的主要因素,在一定程度上,盗蜜强度对繁殖成功具有中性的影响。本研究结果为阐明高山鼠尾草物种的繁殖如何受气候环境变化的影响,以及保证繁殖成功的可能策略奠定基础。     

Effect of aromatic plant species on vesicular-arbuscular mycorrhizal establishment in Pistacia terebinthus

The inoculation of Pistacia terebinthus with vesicular-arbuscular mycorrhizal (VAM) fungi and the spread of the infection were studied using a mixed cropping system, under glasshouse conditions, with Salvia officinalis, Lavandula officinalis and Thymus vulgaris colonized by Glomus mosseae as an inoculation method. This method was compared with soil inoculum placed under the seed or distributed evenly in the soil. Indirect inoculation with all the aromatic plants tested significantly increased VAM root colonization of P. terebinthus compared with the use of soil inoculum, although the effect on plant growth was different for each one of the aromatic species used as inoculum source. Inoculation with L. officinalis and T. vulgaris were the best treatments resulting in high VAM colonization and growth enhancement of P. terebinthus.     

Analysis of expressed sequence tags derived from pea leaves infected by Peronospora viciae f. sp. pisi

A cDNA library was constructed from field pea leaves infected by the downy mildew pathogen, Peronospora viciae f. sp. pisi, using a suppression subtractive hybridisation approach. The library consists of 399 expressed sequence tags, from which 207 unisequences were obtained after sequence assembly. Of the unisequences, six were shown to be of Peronospora viciae f. sp. pisi origin. The remaining unisequences were subjected to gene ontology analysis and their functions were predicted in silico. Eleven of these unisequences (representing 24 clones) shared significant sequence similarities with Arabidopsis genes known to be involved in downy mildew resistance, including the well‐characterised genes RPP5, RPP6 and RPP27. Expression analysis of five selected unisequences by real‐time PCR indicated that all five were up‐regulated during downy mildew pathogenesis, suggesting a significant role for these genes in the host response to downy mildew infection.