Pathogenicity of the root-knot nematode Meloidogyne javanica on potato

Host–parasite relationships and pathogenicity of Meloidogyne javanica on potatoes (newly recorded from Malta) were studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to M. javanica under natural and artificial infections, respectively. In potato tubers, M. javanica induced feeding sites that consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P ) [0–64 eggs + second-stage juveniles (J2s) per cm 3 soil] and growth of cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m + (1 − m ) z ( P − T ) ] was fitted to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits ( T ) for fresh shoot weight and shoot height of cv. Spunta plants infected with M. javanica were 0·50 and 0·64 eggs + J2s per cm 3 soil, respectively. The m parameter in that model (i.e. the minimum possible y -values) for fresh shoot weight and shoot height were 0·60 and 0·20, respectively, at P = 64 eggs + J2s per cm 3 soil. Root galling was proportional to the initial nematode population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density ( P = 4 eggs + J2s per cm 3 soil).peer-reviewe

A survey of potential insect vectors of the plant pathogenic bacterium Xylella fastidiosa in three regions of Spain

The emergence of a rapid-spreading olive disease associated with Xylella fastidiosa in southern Italy represents a high risk to susceptible crops in other countries of the Mediterranean basin, if insect vectors occur in the region. The goal of this study was to identify xylem-feeding Auchenorrhyncha that could potentially act as vectors of X. fastidiosa in three regions of Spain (Andalucía, Murcia and Madrid). Samplings with sweep net and stem tap were carried out in October/2004 on grapevines and adjacent crops (olives, nectarine, citrus, Prunus spp.), ornamental trees and herbaceous weeds. Yellow sticky cards were placed in ten vineyards located across 100 km in Andalucía and in three vineyards distant 10-15 km apart in Murcia. Specimens of frequently-trapped species were tested by nested- or multiplex-PCR for the presence of X. fastidiosa. The Typhlocybinae leafhopper, Austroasca (Jacobiasca) lybica (Hemiptera: Cicadellidae) was the most abundant species in vineyards and citrus orchards. Planthoppers (Hemiptera: Fulgoroidea) and psyllids (Hemiptera: Psylloidea) were prevalent on olives. Cicadellinae leafhoppers (known as sharpshooters), which are major vectors of X. fastidiosa in the Americas, were not found in the samples. The only potential vectors were spittlebugs (Hemiptera: Cercopoidea) collected on Populus sp., herbaceous and on conifer trees (Pinus halepense); the spittlebug Neophileanus sp. was common on conifer trees adjacent to a vineyard in Jumilla. None of the insect samples tested positive for X. fastidiosa by PCR assays. However, spittlebugs already associated with susceptible crops in Spain may allow fast spread of X. fastidiosa in case this pathogen is introduced.We also acknowledge financial support from the CNPq-CSIC bilateral grant no. 2004BR0004 and EU grant ICA4-CT-2001-10005.Peer Reviewe

Método para la detección, identificación y cuantificación de Peronospora arborescens por PCR cuantitativa en tiempo real

Método para la detección, identificación y cuantificación de Peronospora arborescens por PCR cuantitativa en tiempo real. El método para la cuantificación de Peronospora arborescens por PCR cuantitativa (qPCR) en una muestra biológica, comprende extraer el ADN contenido en dicha muestra biológica y amplificarlo mediante qPCR. De aplicación en la cuantificación de P. arborescens.Peer reviewedConsejo Superior de Investigaciones Científicas (España), ALCALIBER SA, Universidad de CórdobaA1 Solicitud de patentes con informe sobre el estado de la técnic

Combined use of a new SNP-based assay and multilocus SSR markers to assess genetic diversity of Xylella fastidiosa subsp. pauca infecting citrus and coffee plants

Two haplotypes of Xylella fastidiosa subsp. pauca (Xfp) that correlated with their host of origin were identified in a collection of 90 isolates infecting citrus and coffee plants in Brazil, based on a single-nucleotide polymorphism in the gyrB sequence. A new single-nucleotide primer extension (SNuPE) protocol was designed for rapid identification of Xfp according to the host source. The protocol proved to be robust for the prediction of the Xfp host source in blind tests using DNA from cultures of the bacterium, infected plants, and insect vectors allowed to feed on Xfp-infected citrus plants. AMOVA and STRUCTURE analyses of microsatellite data separated most Xfp populations on the basis of their host source, indicating that they were genetically distinct. The combined use of the SNaPshot protocol and three previously developed multilocus SSR markers showed that two haplotypes and distinct isolates of Xfp infect citrus and coffee in Brazil and that multiple, genetically different isolates can be present in a single orchard or infect a single tree. This combined approach will be very useful in studies of the epidemiology of Xfp-induced diseases, host specificity of bacterial genotypes, the occurrence of Xfp host jumping, vector feeding habits, etc., in economically important cultivated plants or weed host reservoirs of Xfp in Brazil and elsewhere [Int Microbiol 2015; 18(1):13-24]Keywords: Citrus variegated chlorosis · coffee leaf scorch · vector transmission· xylem-limited bacteria · haplotype characterization · host-plant associatio

Combined use of a new SNP-based assay and multilocus SSR markers to assess genetic diversity of Xylella fastidiosa subsp. pauca infecting citrus and coffee plants

Two haplotypes of Xylella fastidiosa subsp. pauca (Xfp) that correlated with their host of origin were identified in a collection of 90 isolates infecting citrus and coffee plants in Brazil, based on a single-nucleotide polymorphism in the gyrB sequence. A new single-nucleotide primer extension (SNuPE) protocol was designed for rapid identification of Xfp according to the host source. The protocol proved to be robust for the prediction of the Xfp host source in blind tests using DNA from cultures of the bacterium, infected plants, and insect vectors allowed to feed on Xfp- infected citrus plants. AMOVA and STRUCTURE analyses of microsatellite data separated most Xfp populations on the basis of their host source, indicating that they were genetically distinct. The combined use of the SNaPshot protocol and three previously developed multilocus SSR markers showed that two haplotypes and distinct isolates of Xfp infect citrus and coffee in Brazil and that multiple, genetically different isolates can be present in a single orchard or infect a single tree. This combined approach will be very useful in studies of the epidemiology of Xfp- induced diseases, host specificity of bacterial genotypes, the occurrence of Xfp host jumping, vector feeding habits, etc., in economically important cultivated plants or weed host reservoirs of Xfp in Brazil and elsewhere [Int Microbiol 2015; 18(1):13-24].We acknowledge financial support from the EU grant ICA4-CT-2001-10005 and an ‘Intramural Project’ to B. B. Landa from the Spanish National Research Council (CSIC), as well as CNPq for a scholarship to J. R. S. Lopes in Brazil.Peer reviewe

First report of root-knot nematode Meloidogyne hispanica infecting grapevines in southern Spain

Artículo open access.Some commercial vineyards producing the ‘Condado de Huelva’ wine denomination of origin in Almonte, Bonares, and Rociana (Huelva Province), southern Spain, showed general decline in sandy soils in 2009. Disease surveys revealed severe infections of grapevine rootstock Richter 110 feeder roots and heavy soil infestations by a root-knot nematode (Meloidogyne sp.).Peer Reviewe

Consideraciones sobre la situación de Xylella fastidiosa en la Unión Europea y en España. Conclusiones y perspectivas

La primera reflexión que surge es que, desgraciadamente, se ha cumplido la premonición que A. H. Purcell escribió hace ahora veinte años (Purcell, 1997). El mayor experto norteamericano en X. fastidiosa y sus vectores argumentaba que, aunque esta bacteria solo se había encontrado en países americanos y en Taiwán, el hecho de que se hubiera detectado en la década de 1990 en cítricos y en adelfa, causando nuevas enfermedades que se extendían con gran rapidez, sugería que fuera de América se debían mantener medidas de vigilancia fitosanitaria, para evitar su introdución: Previously unrecorded plant diseases in citrus and oleander caused by Xylella fastidiosa have rapidly spread, suggesting that vigilant phytosanitary measures outside America, should be maintained against its introduction. Y él se hacía las preguntas clave: ¿es esta bacteria una amenaza potencial para otros continentes? ¿Es un problema regional o una amenaza global? Ahora es fácil responder, tras las detecciones europeas en Italia, Alemania, Francia y España: se trata de una amenaza global, por tratarse de una bacteria con mucha más capacidad de afectar a múltiples especies vegetales y que está causando muchas más pérdidas, al menos en Italia, de lo que se podía sospechar en 1997. La advertencia de Purcell no tuvo suficiente eco, ya que los países de la UE parecían más interesados en aprovechar las ventajas del comercio global que en protegerse de las graves enfermedades y de las plagas que podían ser introducidas con los productos importados. Así debió introducirse X. fastidiosa en la UE, siendo transportada en avión o en barco con plantas ornamentales u otros tipos de material vegetal infectado, procedente de países del continente americano

Rethinking the Xylella fastidiosa scenario in the Balearic Islands: what epidemiological, phylogenetic and dendrochronological data tell us

Trabajo presentado en la 2nd European conference on Xylella fastidiosa (how research can support solutions), celebrada en Ajaccio el 29 y 30 de octubre de 2019.The emergence of Xylella fastidiosa(Xf) in Europe has been dealt as relatively recent introductions from the American continent. While this seems accurate for highly virulent genotypes such as thestrain currently causing the quick olive decline syndrome in Apulia since ca. 2013, less virulent Xf genotypes might have gone undetected for a long time, being confused with drought or fungal disease symptoms under Mediterranean climatic conditions. Indeed, the current widespread incidence and severity of the Pierce’s disease (PD) and Almond Leaf Scorch Disease (ALSD) in Mallorca Island can only be understood in this context of a 20-year introduction scenario. Our current epidemiological, phylogenetic anddendrochronological data onXf strains belonging to subsp. fastidiosaST1, and Xf subsp. multiplexST81, causing Pierce’s disease (PD) and ALSD, respectively, strongly suggest that they were overlooked for decades. Both subspecies were very likely transported from California to Mallorca with infected almond scions around 1995 and subsequently spread throughout the island by the local vector Philaenus spumarius. Our phylogenetic analysis based on WGS of isolates of both subspecies from Mallorca supports their Californian origin. Congruent with this, Xf DNA was consistently detected in the growing rings of infected almond trees from 2006 to the present and occasionally as far back as 1998. In the main focus in Son Carrió more than 50% of the almond trees diedand 90% of trees showed symptoms compatible with ALSD in 2012, but the aetiology of this problem was attributed to fungal trunk diseases, drought or field abandonment. We hypothesise that during the last 20 years, Xf subsp. multiplexST81 isolates have adapted to wild olive trees, widespread on the island, causing a mild dieback, and later on reaching the island of Menorca very likely on infected P. spumariustransported as a hitchhiker on ships moving between the islands.This research was funded by project E-RTA2017-00004-C06 from AEI-INIA Spain and FEDER and received financial support from the Ministry of Agriculture, Fishery and Food (Dirección General de la Sanidad de la Producción Agrària) of Spain and from ‘Govern de les Illes Balears’

Correlation of banana productivity levels and soil morphological properties using regularized optimal scaling regression

Soil morphological properties described in the field, such as texture, consistence or structure, provide a valuable tool for the evaluation of soil productivity potential. In this study, we developed a regression model between the soil morphological variables of banana plantations and a crop Productivity Index (PI) previously developed for the same areas in Venezuela. For this, we implemented categorical regression, an optimal scaling procedure in which the morphological variables are transformed into a numerical scale, and can thus be entered in a multiple regression analysis. The model was developed from data from six plantations growing “Gran Nain” bananas, each with two productivity levels (high and low), in two 4-ha experimental plots, one for each productivity level. Sixty-three A horizons in thirty-six soils were described using 15 field morphological variables on a nominal scale for structure type, texture and hue, and an ordinal scale for the rest (structure grade, structure size, wet and dry consistence, stickiness, plasticity, moist value, chroma, root abundance, root size, biological activity and reaction to HCl). The optimum model selected included biological activity, texture, dry consistence, reaction to HCl and structure type variables. These variables explained the PI with an R2 of 0.599, an expected prediction error (EPE) of 0.645 and a standard error (SE) of 0.135 using bootstrapping, and EPE of 0.662 with a SE of 0.236 using 10-fold cross validation. Our study showed how soil quality is clearly related to productivity on commercial banana plantations, and developed a way to correlate soil quality indicators to yield by using indicators based on easily measured soil morphological parameters. The methodology used in this study might be further expanded to other banana-producing areas to help identify the soils most suitable for its cultivation, thereby enhancing its environmental sustainability and profitability