Abstract
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. The characterization of the vmp1 gene revealed six different vmp types in grapevines (V1, V4, V9, V11, V12, V24), three in weeds (V4, V9, V11), and four in insects (V4, V9, V11, V24). Notably, V4, V9, appear both in hosts and vectors, with V9 predominant. Virtual restriction fragment length polymorphism (RFLP) analysis based on the nucleotide sequences supported the data of the conventional RFLP. Connections between the molecular data recorded in the vineyard ecosystems and the application of innovative tools based on the geostatistical analysis will contribute to further clarification of the specific ecological and epidemiological aspects of ‘Ca. P. solani’ in Sicily.
Highlights
Bois noir (BN) is caused by ‘Candidatus Phytoplasma solani’ 16SrXII-A ribosomal subgroup [1].This pathogen has a large host spectrum and its main vectors for transfer to grapevine are the polyphagous cixids Hyalesthes obsoletus and Reptalus panzeri (Loew) [2,3].Pathogens 2020, 9, 918; doi:10.3390/pathogens9110918 www.mdpi.com/journal/pathogensRecently, in grapevine-growing areas of northern Italy where the presence of the main vector is low, Quaglino et al [4] claimed that the occurrence of BN suggests the involvement of alternative vectors
Grapevine is considered a dead-end host for ‘Ca. P. solani’, and the spatial spread of BN most likely is not based on the spreading of ‘Ca. P. solani’ from grapevine to grapevine, but through other plant species, as both spontaneous and cultivated
Symptoms of grapevine yellows were observed in both years of the survey (2014, 2015)
Summary
Bois noir (BN) is caused by ‘Candidatus Phytoplasma solani’ 16SrXII-A ribosomal subgroup [1].This pathogen has a large host spectrum and its main vectors for transfer to grapevine are the polyphagous cixids Hyalesthes obsoletus and Reptalus panzeri (Loew) [2,3].Pathogens 2020, 9, 918; doi:10.3390/pathogens9110918 www.mdpi.com/journal/pathogensRecently, in grapevine-growing areas of northern Italy where the presence of the main vector is low, Quaglino et al [4] claimed that the occurrence of BN suggests the involvement of alternative vectors. Bois noir (BN) is caused by ‘Candidatus Phytoplasma solani’ 16SrXII-A ribosomal subgroup [1] This pathogen has a large host spectrum and its main vectors for transfer to grapevine are the polyphagous cixids Hyalesthes obsoletus and Reptalus panzeri (Loew) [2,3]. Grapevine is considered a dead-end host for ‘Ca. P. solani’, and the spatial spread of BN most likely is not based on the spreading of ‘Ca. P. solani’ from grapevine to grapevine, but through other plant species, as both spontaneous and cultivated. Spatial pattern analysis has shown that BN incidence can be higher near vineyard borders This strongly suggests inward movement of the vectors from spontaneous plants growing nearby, as well as within vineyard associations between spontaneous plants, H. obsoletus, and diseased grapevines [5,8,9,10,11]
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