Statistical modeling of long-term grapevine response to ‘Candidatus Phytoplasma solani’ infection in the field (original) (raw)
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Ecosphere, 2015
Insect-vectored plant diseases often create complex epidemiological systems that are challenging to understand, predict, and manage. An example is 'bois noir' (BN), a phytoplasma-associated grapevine disease commonly found in European vineyards. Although BN has the potential to cause substantial economic damage, the factors that contribute to BN prevalence in vineyards are still not well understood. We used Bayesian inference with generalized linear mixed-effect models to test the hypotheses that (1) grapevine varieties exhibit different BN susceptibility; (2) environment drivers influence prevalence of the disease and occurrence of the vector; and (3) the presence of the main vector is a major determinant of BN occurrence. We found that the presence of the vector Hyalesthes obsoletus increased with increasing isothermality, minimum temperatures during the coldest period, soil erosion, and natural vegetation in close proximity to the vineyards. Presence of the BN disease increased with presence of the vector as well as increasing altitudes and mean annual temperatures. After accounting for those factors, Chardonnay and Riesling showed higher disease prevalence than Mü ller-Thurgau, Silvaner, and Merlot. Although the vector had an overall positive effect on the disease prevalence, disease and vector occurrence show distinct spatial patterns. In conclusion, our analysis suggests that vector presence is not the only, and maybe not the most important factor for BN disease prevalence. Environment and grape cultivar also play important roles. Hence, area-wide predictions of both environmental disease risk and vector presence, together with information about the susceptibility of grape cultivars, will enable a more targeted disease management. Our modelling framework could easily be applied to other diseases of concern, such as apple proliferation or flavescence dorée.
Pathogens
Bois noir is caused by ‘Candidatus Phytoplasma solani’, and it is one of the most important and widespread diseases in the Euro-Mediterranean region. There are complex interactions between phytoplasma and grapevines, weeds, and vectors. These ecological relationships can be tracked according to molecular epidemiology. The aims of the 2-year study (2014–2015) were to describe incidence and spatial distribution of Bois noir in a vineyard with three grapevine varieties in Sicily, and to identify the molecular types of the tuf and vmp1 genes in these naturally infected grapevines, according to the potential reservoir plants and vectors. Disease incidence in 2015 was significantly higher in ‘Chardonnay’ (up to 35%) than for ‘Nero d’Avola’ and ‘Pinot noir’ (<5%). All grapevine, weed, and insect samples were infected by ‘Ca. P. solani’ tuf-type b. Most of the collected insects were strictly related to Vitis spp. and belonged to Neoaliturus fenestratus, Empoasca spp., and Zygina rhamni. ...
European Journal of Plant Pathology, 2015
Bois noir (BN), which is induced by 'Candidatus Phytoplasma solani' ('Ca. P. solani'), is an important grapevine yellows disease that causes severe damage in viticultural regions throughout the Euro-Mediterranean basin. An epidemiological survey to determine potential insect vectors and the primary reservoir plants of BN phytoplasma in Macedonian vineyards was undertaken between 2012 and 2013 in the southeastern part of the country. A study on the species diversity from the suborder Auchenorrhycha revealed the prevalence of the principal vector of 'Ca. P. solani', which is the planthopper Hyalesthes obsoletus. Reptalus panzeri, which is the second-most documented BN vector, was not recorded in Macedonian vineyards. Three leafhopper species, namely Psammotettix alienus, Artianus manderstjernii and Euscelis incisus, were also widespread in the BNaffected vineyards, but only H. obsoletus tested positive for 'Ca. P. solani'. Molecular characterizations were performed by the sequencing and/or RFLP typing of tuf, vmp1 and stamp genes, and the results were used to gain detailed insight into the molecular diversity of the 'Ca. P. solani' strains associated with grapevines, tentative reservoir plants (Urtica dioica and Convolvulus arvensis) and the H. obsoletus associated with these plants. Among the 91 'Ca. P. solani' strains detected in diverse plant and insect hosts, three tuf, five vmp1 and 11 distinct stamp genotypes were identified. Twelve comprehensive genotypes of 'Ca. P. solani' were detected according to the tuf/vmp1/stamp genotyping. The highest diversity of genotypes was detected among the strains from H. obsoletus individuals associated with U. dioica, of which the most frequent genotype was tuf-ab/V18/M1 (43 %). The tuf-b/V2-TA/STOL comprehensive genotype was found in 33 % of naturally infected grapevines. Two 'Ca. P. solani' genotypes were associated with U. dioica, namely (i) tuf-ab/V18/M1 (60 %) and tuf-a/V3/M4 (40 %), and only one genotype (tuf-b/V2-TA/Rqg50) was associated with C. arvensis.
Plants, 2021
Ripe rot caused by Colletotrichum spp. is a serious threat in many vineyards, and its control relies mainly on the repeated use of fungicides. A mechanistic, dynamic model for the prediction of grape ripe rot epidemics was developed by using information and data from a systematic literature review. The model accounts for (i) the production and maturation of the primary inoculum; (ii) the infection caused by the primary inoculum; (iii) the production of a secondary inoculum; and (iv) the infection caused by the secondary inoculum. The model was validated in 19 epidemics (vineyard × year combinations) between 1980 and 2014 in China, Japan, and the USA. The observed disease incidence was correlated with the number of infection events predicted by the model and their severity (ρ = 0.878 and 0.533, respectively, n = 37, p ≤ 0.001). The model also accurately predicted the disease severity progress during the season, with a concordance correlation coefficient of 0.975 between the observed ...
Infection, Genetics and Evolution, 2015
a b s t r a c t 'Candidatus Phytoplasma solani' is a phytoplasma of the stolbur group (16SrXII subgroup A) that is associated with 'Bois noir' and causes heavy damage to the quality and quantity of grapevine yields in several European countries, and particularly in the Mediterranean area. Analysis of 'Ca. P. solani' genetic diversity was carried out for strains infecting a cv. 'Chardonnay' vineyard, through multilocus sequence typing analysis for the vmp1, stamp and secY genes. Several types per gene were detected: seven out of 20 types for vmp1, six out of 17 for stamp, and four out of 16 for secY. High correlations were seen among the vmp1, stamp and secY typing with the tuf typing. However, no correlations were seen among the tuf and vmp1 types and the Bois noir severity in the surveyed grapevines. Grouping the 'Ca. P. solani' sequences on the basis of their origins (i.e., study vineyard, Italian regions, Euro-Mediterranean countries), dN/dS ratio analysis revealed overall positive selection for stamp (3.99, P = 0.019) and vmp1 (2.28, P = 0.001). For secY, the dN/dS ratio was 1.02 (P = 0.841), showing neutral selection across this gene. Using analysis of the nucleotide sequencing by a Bayesian approach, we determined the population structure of 'Ca. P. solani', which appears to be structured in 3, 5 and 6 subpopulations, according to the secY, stamp and vmp1 genes, respectively. The high genetic diversity of 'Ca. P. solani' from a single vineyard reflects the population structure across wider geographical scales. This information is useful to trace inoculum source and movement of pathogen strains at the local level and over long distances.
European Journal of Plant Pathology, 2014
The available knowledge on black-rot of grape was retrieved from literature, analyzed, and synthesized to develop a mechanistic model of the life cycle of the pathogen (Guignardia bidwelii) based on the systems analysis. Three life-cycle compartments were defined: (i) production and maturation of inoculum in overwintered sources (i.e., ascospores from pseudothecia and conidia from pycnidia in berry mummies and cane lesions); (ii) infection caused by ascospores and conidia; and (iii) disease onset and production of secondary inoculum. An analysis of published, quantitative information was conducted to develop a mechanistic model driven by weather and vine phenology; equations were developed for ascospore and conidial maturation in overwintered fruiting bodies, spore release and survival, infection occurrence and severity, incubation and latency periods, onset of lesions, production of pycnidia, and infectious periods. The model was then evaluated for its ability to represent the real system and its usefulness for understanding black-rot epidemics by using three typical epidemics. Finally, weaknesses in our knowledge are discussed. Additional research is needed concerning the influence of wetness duration and temperature on infection by ascospores, production dynamics of pycnidia and conidia in black-rot lesions, and the dynamics of conidia exudation from pycnidia.
Pathogens, 2020
Bois noir (BN), associated with ‘Candidatus Phytoplasma solani’ (CaPsol), is the most widespread disease of the grapevine yellows complex worldwide. In this work, BN epidemiology was investigated in a case study vineyard where an unusual CaPsol strain, previously detected only in other host plants, was found to be prevalent in grapevine. Experimental activities included: symptom observation; sampling of symptomatic vines, Auchenorrhyncha specimens, and weeds; molecular detection and typing of CaPsol strains; statistical analyses for determining possible relationships between CaPsol relative concentration, strain type, and symptom severity. Among insects, Reptalus quinquecostatus was the most abundant and was found to be highly infected by CaPsol, while Hyalesthes obsoletus, the main CaPsol vector, was not caught. Moreover, R. quinquecostatus harbored CaPsol strains carrying uniquely the stamp sequence variant St10, also identified as prevalent in vines and in the majority of weeds, ...
PLOS ONE, 2015
A mechanistic model for Botrytis cinerea on grapevine was developed. The model, which accounts for conidia production on various inoculum sources and for multiple infection pathways, considers two infection periods. During the first period ("inflorescences clearly visible" to "berries groat-sized"), the model calculates: i) infection severity on inflorescences and young clusters caused by conidia (SEV1). During the second period ("majority of berries touching" to "berries ripe for harvest"), the model calculates: ii) infection severity of ripening berries by conidia (SEV2); and iii) severity of berry-to-berry infection caused by mycelium (SEV3). The model was validated in 21 epidemics (vineyard × year combinations) between 2009 and 2014 in Italy and France. A discriminant function analysis (DFA) was used to: i) evaluate the ability of the model to predict mild, intermediate, and severe epidemics; and ii) assess how SEV1, SEV2, and SEV3 contribute to epidemics. The model correctly classified the severity of 17 of 21 epidemics. Results from DFA were also used to calculate the daily probabilities that an ongoing epidemic would be mild, intermediate, or severe. SEV1 was the most influential variable in discriminating between mild and intermediate epidemics, whereas SEV2 and SEV3 were relevant for discriminating between intermediate and severe epidemics. The model represents an improvement of previous B. cinerea models in viticulture and could be useful for making decisions about Botrytis bunch rot control.
European Journal of Plant Pathology, 2015
Bois noir is one of the most important diseases caused by 'Candidatus Phytoplasma solani' affecting grapevine in the Euro-Mediterranean area. 'Ca. P. solani' characterization plays a significant role in its diagnosis, control and understanding of its epidemiology. In the present study, two genes encoding membrane proteins, namely vmp1 and stamp, were used to assess the genetic variability of 18 'Ca. P. solani' grapevine isolates from the Herzegovina region (B&H), previously characterised as tuf-b type. Nested-PCR/RFLP and sequence analyses of vmp1 gene showed the presence of three profiles V17, V14 and V4 where V17 was highly prevalent. Phylogenetic analysis of stamp gene revealed the presence of four different genotypes, where Rqg50 was the most frequent. Finally, the combined results of tuf, vmp1 and stamp genes, reported three previously identified genotypes from Serbia, Austria and Montenegro, and two newly described ones (DB1 and DB2). Although performed only on 'Ca. P. solani' isolates from infected grapevines, this study provides useful molecular information to get better insight on BN epidemiology in B&H.
Annals of Applied Biology, 2014
A multidisciplinary approach, based on field surveys, molecular biology techniques, and spatial data analyses, was utilised to investigate the Bois noir (BN) epidemiology in northeastern Italian vineyards during the years 2010-12. Symptomatic grapevines, weeds and specimens of the insect vector Hyalesthes obsoletus were monitored and mapped. Leaf samples from symptomatic grapevines and weeds, and captured insect specimens were analyzed by real-time PCR to identify BN phytoplasma (BNp; 'Candidatus Phytoplasma solani' species), the etiological agent of BN. Data spatial distribution was analyzed using SADIE (Spatial Analysis by Distance IndicEs). Bois noir phytoplasma strains identified in weed candidates for an epidemiological role were characterised by RFLP-based analyses of tuf gene amplicons. Results highlighted that, in the examined areas, the host systems Convolvulus arvensis-H. obsoletus and Urtica dioica-H. obsoletus play the main role in BN diffusion. It was also evidenced that other weeds (i.e. Chenopodium album and Malva sylvestris) spatially associated with symptomatic grapevines and/or insect vectors and infected by the same tuf type identified in grapevines and insects, could play a role in BN diffusion. On the other hand, some weeds (i.e. Trifolium repens) were uninfected and not associated with symptomatic grapevines and/or insect vectors. The synergic application of our multidisciplinary approach improved the knowledge of BN epidemiology, and provided helpful indication for designing experimental plans to contain BN spreading in vineyards through weed management. The approach described in the present work could be used to investigate the complex epidemiology of other phytoplasma diseases.