Pathogenicity of Meloidogyne incognita and M. javanica on recombinant inbred lines from a crossing of Cucurbita pepo subsp. pepo × C. pepo subsp. ovifera

The response of recombinant inbred lines (RILs) from a cross of zucchini × scallop (Cucurbita pepo subsp. pepo ‘Murcia MU-CU-16’ × C. pepo subsp. ovifera ‘Scallop UPV-196’) to Meloidogyne incognita and M. javanica was determined after completion of a nematode reproduction cycle in experiments carried out in a growth chamber. The nematode differentiated the C. pepo genotypes at the subspecies level due to lower egg mass production on subspecies pepo than ovifera, and thus subspecies pepo was a poorer host than ovifera. In addition, Murcia MU-CU-16 discriminated M. incognita from M. javanica in terms of egg masses (EM), eggs per gram of root and reproduction factor (Rf), whereas Scallop UPV-196 did so in eggs per gram of root and Rf. The RILs differed in gall formation and EM production depending on the nematode × line combination. Comparisons between nematode isolates resulted in four significant combinations for pathogenic potential (galls/initial population (Pi) × 100), seven for parasitic success (egg masses/Pi × 100), and nine for host efficiency (egg masses/galls per root system × 100) which included all the lines tested against both isolates. Lines that restricted nematode development by at least 90% were considered as having intermediate resistance to M. incognita based on the definition of the International Seed Federation. They included lines 28-1, 35A, 107A, 110-3 and 153-2. All the RILs were susceptible hosts for M. javanica. The information presented here will be helpful for nematode management and also for plant breeders working on pathogen resistance on C. pepo.     

A new species of <Emphasis Type="Italic">Microterys</Emphasis> (Hymenoptera: Encyrtidae) from Northeast China,parasitoid of <Emphasis Type="Italic">Parthenolecanium corni</Emphasis> (Bouché) (Hemiptera: Coccidae)

A new species of Microterys Howard (Hymenoptera: Encyrtidae), M. angustus Zu, Li & Wang sp. nov., is described from China as a parasitoid of Parthenolecanium corni (Bouché) (Hemiptera: Coccidae) on Acer saccharum Marsh. and Sophora japonica Linn..     

A new species of <Emphasis Type="Italic">Anagyrus</Emphasis> (Hymenoptera: Encyrtidae) from China,parasitoid of <Emphasis Type="Italic">Phenacoccus solani</Emphasis> Ferris (Hemiptera: Pseudococcidae) on <Emphasis Type="Italic">Lycoris radiata</Emphasis> (L’Her.) Herb.

A new species of Anagyrus Howard (Hymenoptera: Encyrtidae), A. pseudofuscus Zu sp. nov., is described from China as a parasitoid of the mealybug, Phenacoccus solani Ferris (Hemiptera: Pseudococcidae).     

Functional response of <Emphasis Type="Italic">Geocoris ochropterus</Emphasis> Fieber (Hemiptera: Geocoridae) to different egg densities of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hübner) (Lepidoptera: Noctuidae)

The biology and predatory efficiency of Geocoris ochropterus Fieber (Hemiptera: Geocoridae) has been studied extensively against many insect pests, but information on functional response of different stages of G. ochropterus to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is lacking so far. The functional response of different stages of G. ochropterus to varying densities of eggs of H. armigera was investigated in the laboratory at 26?±?2°C, 65?±?2% RH and 12 L: 12D. Immature stages i.e. 3rd, 4th, 5th instar and adult predator exhibited type II functional response. Handling time decreased with increasing predator’s developmental stage. Adult G. ochropterus followed by fifth instar exhibited highest egg consumption and attack rate compared to other stages. Functional response parameters indicate that the adult and fifth instar of G. ochropterus were more voracious and efficient than other juveniles and might be useful as promising biocontrol agent against H. armigera.     

Scientific critique of the paper “Climatic distribution of citrus black spot caused by <Emphasis Type="Italic">Phyllosticta citricarpa</Emphasis>. A historical analysis of disease spread in South Africa” by Martínez-Minaya et al. (2015)

The global distribution of citrus black spot (CBS) disease, caused by Phyllosticta citricarpa, is climatically constrained, which is evident from its occurrence in citrus growing areas with warm, summer rainfall and its absence from areas with cooler, Mediterranean-type winter rainfall. Various epidemiological and modelling studies have supported this observation, predominantly estimating unsuitability for P. citricarpa in Mediterranean type climates, with no more than marginal suitability estimated at a few localities within some regions with Mediterranean type climates. The study by Martínez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015), describes an historic sequence of recorded CBS occurrence in parts of South Africa, conducts an autocorrelation analysis and a correlative analysis with Köppen-Geiger climate zones and makes observations about the occurrence of certain Köppen-Geiger climate zones in the European Union. The study suggests that significant portions of the European Union and the broader Mediterranean basin are climatically similar to warm, summer rainfall areas in South Africa where P. citricarpa persists and causes CBS disease and concludes that the potential distribution of P. citricarpa is less constrained by climatic factors than spatial contagion. However, in this critique we expose methodological shortcomings in the Martínez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015) study and conclude that the study grossly overestimated the extent of the geographical area that could support P. citricarpa, thereby rendering the findings scientifically unreliable.     

Lamb’s lettuce (Valerianella olitoria): new host of Fusarium oxysporum f. sp. conglutinans

Journal of Plant Diseases and Protection - A new wilt of lamb’s lettuce (Valerianella olitoria) was detected in northern Italy in 2003 and the causal agent of the disease was identified as...     

Structure of populations of wheat powdery mildew (Erysiphe graminis DC f.sp. tritici Marchal) in Central Europe in 1993–1996: I. Dynamics of virulence

In 1993–1996, the virulence of regional populations of the wheat powdery mildew pathogen (Erysiphe graminis DC f. sp. tritici Marchal) from the Czech Republic, Austria, Hungary and Slovakia against 13 resistance genes was investigated. The populations differed mainly at the regional level. Populations from the Czech Republic, mainly from the western regions, showed higher values of virulence against the Pm4b gene. Lower frequency of virulence against Pm4b was found in Austria, and the lowest value was observed in Hungary. The differences in frequencies of virulence against Pm4a and Pm4b showed a similar geographic pattern across the four countries: a continuous decline from west to east and from north to south. Virulence against Pm2 decreased in all countries considered; virulence to pm5, Pm6, Pm8 and Mli was high throughout. Genes and gene combinations that can ensure a relatively effective biological protection against this pathogen across Central Europe at present are Pm3b, Pm2+Mld and Pm1+2+9. Czech and Slovak populations were the most complex: virulence complexity reached a maximum in Slovakia in 1994. A similar evolution, though less significant, was observed in the Czech Republic. Data on complexity of isolates suggest that Central European populations of wheat powdery mildew tend to reach an intermediate level representing the optimal number of virulence genes. This process is probably a consequence of stabilizing selection.     

First report of the citrus leafhopper <Emphasis Type="Italic">Penthimiola bella</Emphasis> (Stål) (Hemiptera,Cicadellidae) in Europe

The presence of the citrus leafhopper, Penthimiola bella (Stål) (Hemiptera, Cicadellidae), was detected in citrus orchards in Portugal. This is the first report of this cicadellid in Europe. A survey was carried out in 30 citrus orchards in Algarve, in southern Portugal, based on both the beating method and visual observation of shoots, between July and December 2012. P. bella was detected in a total of 19 orchards distributed throughout the region. The occurrence of reproducing populations of P. bella and its dispersion over a relatively large area of at least 70 km in length within Algarve suggests that this species established and has been expanding its distribution in the region for several years since its arrival. The possible pathway of introduction and its pest status are discussed.     

Response to the letter on “Climatic distribution of citrus black spot caused by <Emphasis Type="Italic">Phyllosticta citricarpa.</Emphasis> A historical analysis of disease spread in South Africa” by Fourie et al. (2017)

In a previous study, Martínez-Minaya et al. (European Journal of Plant Pathology 143, 69–83, 2015) performed an analysis of climate-based distribution of citrus black spot (CBS) in South Africa. It was found that CBS was initially confined to humid areas with summer rainfall, but later spread to arid steppe and even desert climates. A strong spatial autocorrelation of CBS distribution was found. Fourie et al. (European Journal of Plant Pathology, 2017) take a critical view of our study, but without presenting any analysis of results to refute our findings. Furthermore, Fourie et al. (European Journal of Plant Pathology, 2017) appear to have misunderstood our work, since many of their criticisms relate to the potential distribution of CBS in Europe, which is beyond the scope of our original study. Fourie et al. (European Journal of Plant Pathology, 2017) highlight the limitations of climate classifications in species distribution modelling. However, this was made explicit in our study, indicating that it was a preparatory work and further advanced modelling studies, including spatial effects, will be needed. Fourie et al. (European Journal of Plant Pathology, 2017) incorrectly assume that we used all of South Africa as the background in the spatial autocorrelation analysis. However, only citrus areas were used and a strong spatial autocorrelation was detected at all distances evaluated. Contrary to what Fourie et al. (European Journal of Plant Pathology, 2017) suggest, similar climate distributions of CBS were obtained at 5′ and 30′ resolution, and also with the national land-cover map of South Africa. The figure comparison presented by Fourie et al. (European Journal of Plant Pathology, 2017) appears to ignore the fact that the maps we used were grid cells of 10 × 10 km and not the line polygons they suggest. Therefore, we consider the conclusions from the Martínez-Minaya et al. (European Journal of Plant Pathology 143, 69–83, 2015) remain entirely valid.     

Virulence structure of the <Emphasis Type="Italic">Blumeria graminis</Emphasis> DC.f. sp. <Emphasis Type="Italic">avenae</Emphasis> populations occurring in Poland across 2010–2013

The aim of the present study was to determine the virulence structure of powdery mildew of oats (Blumeria graminis DC.f. sp. avena) in Poland in the years 2010–2013. For this purpose, powdery mildew isolates were collected from three experimental stations in Poland. To assess the virulence of the isolates, eight oat varieties with different responses to the pathogen were used. The results showed that a significant proportion of powdery mildew isolates found in Poland overcame the resistance genes of varieties Bruno (Pm6), Jumbo (Pm1) and Mostyn (Pm3). In contrast, lines Av1860 (Pm4), Am27 (Pm5) and Cc3678 (Pm2) were completely resistant to all pathogen isolates involved in the experiment. Changes constantly occurring in the powdery mildew population perfectly reflect diversity indexes, which were the smallest in the first year of observation, where in the following years these parameters were significantly higher. It is worth noting that the presence of powdery mildew is seasonal and local, which is reflected in the prevalence of the disease in a defined area of the country.     

Margaritaella gracilis gen. n. et sp. n. (Eucestoda: Proteocephalidea), a parasite of Callichthys callichthys (Pisces: Siluriformes) from the Paraná River basin, Argentina

Margaritaella gracilis gen. n. et sp. n. (Proteocephalidea: Proteocephalinae) found in the intestine of Callichthys callichthys (Linnaeus) from the Paraná River basin is described. The new genus is placed in the Proteocephalinae because of the medullary position of the genital organs. It differs from all known genera included in the Proteocephalinae by the following combination of characters: 1) scolex with a conspicuous cluster of drop-shaped gland cells posterior to suckers; 2) strobila with a low number of proglottides, all much longer than wide; 3) testes arranged in one field, composed of two parallel rows of testes separated by the uterus; 4) ovary delicate, H-shaped, with branches slender and deeply folliculate at the edges, located at 25-35% from the posterior end; 5) uterus largely extended posterior to the ovary but not reaching the end of proglottis; and 6) vitelline follicles in two narrow lateral bands, largely extended posterior to the ovary. Scanning electron microscopy revealed three types of microtriches on the tegument surface: acicular and capiliform filitriches and gladiate spinitriches. The relative size of the ovary, a character recently used in the systematics of the proteocephalidean cestodes, was calculated for the new species and compared with other species of the group. M. gracilis is the first record of a proteocephalidean cestode parasitizing a callichthyid catfish.     

Colonization of rose by Sphaerotheca pannosa (Wallr.) Lév. var. rosae Wor.

Colonization of rose by powdery mildew (Sphaerotheca pannosa) is described in terms of mycelium growth, conidiophore production and sporulation in time. The data used are gathered during different years, put together and treated by means of graphic models. Colonies could be separated into fast and slow growing colonies. Colonies initiated on leaves of increasing age showed a decreasing growth rate. Production of conidiophores and conidia started on the same day, and the relative activity of conidiophore production reached its maximum 6 days after the end of the latency period, followed 1 day later by the maximum activity of conidium production. Both conidiophore and conidium production continued for a long time at a low level. The effect of leaf age on conidiophore production found expression in differences in production rate during the first days of colony development and in final production levels. Observations on naturally infected leaves in an outdoor experiment showed a rapid decrease of sporulation on leaves of 10 days and older. Highest percentages of sporulating leaf area were observed on leaves between 7 and 10 days old.     

Bois noir affects the yield and wine quality of <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. cv. ‘Chardonnay’

The Bois noir (BN) disease induced by ‘Candidatus Phytoplasma solani’ (CPs) is common in European vineyards. Its damage has not been fully investigated, especially with regards to wine attributes. The impact of BN on yield, berry composition and wine characteristics of Vitis vinifera L. cv. ‘Chardonnay’ was therefore comprehensively characterized in a 3-year field experiment in Hungary, Eger winegrowing region. Additionally, the bindweed-related tuf-b1 genotype was identified to be involved in the BN pathosystem in the experimental vineyard. Infection of CPs tuf-b1 genotype resulted in severe yield loss, the average decrease in number of bunches and total yield per vine was 56.7% and 68.4%, respectively. Analyses of wines produced from grapes of BN infected vines revealed decreased alcohol, epicatechin and iron contents; and increased organic acids, titratable acidity, catechin and calcium contents. Sensory evaluation of these wines confirmed unfavourable characteristics, i.e. higher acidity, bitterness, and usually pinkish discolouration. Negative impact on berry composition and wine quality were pronounced in the vintage with favourable weather conditions for grapevine production, whereas the negative effects of BN infection were less prominent, even masked, in the vintages with unfavourable weather (wet and cool). To reduce BN-caused damage, the need for improved preventative and curative measures for BN disease is highlighted.     

Phoma stem canker (<Emphasis Type="Italic">Leptosphaeria maculans/L. biglobosa</Emphasis>) of oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis>): is the G<Subscript>2</Subscript> Disease Index a good indicator of the distribution of observed canker severities?

Several disease indices (DI) have been proposed to assess the severity of phoma stem canker at late growth stages. The DI commonly used in France (called G₂ DI) consists of integrating the distribution of the proportions of plants observed within six canker severity classes into a single index. This index uses arbitrarily chosen coefficients associated to each class of canker severity. A given value of this DI can therefore be obtained with different distributions among the canker severity classes. Consequently, it is important to assess to what extent the G₂ DI is representative of the distribution of plants in canker severity classes. We show in this study that the G₂ DI is a good indicator of the distribution of the observed canker severities, using a dataset from different years, sites and cultivars; this illustrates the robustness of the G₂ DI.     

梭梭(Haloxylon ammodend rom(C.A.Mey)Bunge)光合枝细胞组织学观察及其抗逆性特征

通过细胞组织学解剖方法 ,观察研究梭梭幼嫩光合枝显微结构的抗逆性特征 ,并结合 H2 O2 酶活性的测定 ,得出梭梭光合枝显微结构中有 3点与相关文献报道不同。 1是具有一层海棉组织 ,富含叶绿体 ,细胞体积相对较小 ,为不规则圆球状细胞层 ;2是退化的鳞片状叶表皮层下仍有一层细胞体积小 ,圆形 ,具有明显的细胞核 ,无叶绿体 ,排列紧密的细胞层 ;3是栅栏组织细胞具泌盐的功能 ,并有发育较好的盐结晶存在于细胞之间 ,显示出较强的抗逆特征。     

B.t.杀虫剂的发展、问题及对策(续)

二.B.t.杀虫剂的问题和对策B.t.作为一种生物杀虫剂,与传统的化学杀虫剂相比,有其独特的优点,也有其弱点。主要优点表现为(1)选择性极强,对哺乳动物和非目标生物安全,对生态环境影响小;(2)B.t.具有相当大的开发潜力(如高活性或不同寄主谱的新菌株);(3)成本低。其缺点有(1)寄主谱窄,没有化学杀虫剂那样广谱的杀虫活性;(2)有些天然菌株的杀虫活力低或发酵特性差;(3)田间药效不稳定,作用速度慢,持效期短,药效受环境因素影响较大;(4)抗性问题不容忽视。