Development of Spectral Disease Indices for ‘Flavescence Dorée’ Grapevine Disease Identification

Flavescence dorée phytoplasmas (FDp, 16SrV-C and -D) are plant pathogenic non-cultivable bacteria associated with a severe grapevine disease. The incidence of the two reference strains on cultivated grapevines is unbalanced, and mixed infections are rare. To investigate the interaction between the two strains, Catharanthus roseus plants were graft-infected with both strains, either simultaneously or sequentially. Different combinations of lateral and apical grafting were applied to avoid possible benefits due to graft position. The infection was monitored for four months through a new diagnostic protocol developed for differentiation and relative quantification of the two strains. Regardless of the temporal or spatial advantage at grafting, FD-C generally outcompeted FD-D. The prevalence of FD-C increased over time and, at the end of the experiment, FD-C was the unique strain detected in the aerial part and the roots of 74% and 90% of grafted plants, respectively. These data indicate that the interaction between the two strains results in competitive exclusion. Understanding the bases of the competition between FD-C and FD-D may contribute to explain the biology of the coexistence of different FDp strains under field conditions, aiming at identifying potential suppressor strains, which can provide alternative and environmentally sustainable solutions for FD control.

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Recovery from Grapevine Flavescence Dorée in Areas of High Infection Pressure

Agronomy ◽

10.3390/agronomy10101479 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1479

Author(s):

Matteo Ripamonti ◽

Davide Pacifico ◽

Chiara Roggia ◽

Sabrina Palmano ◽

Marika Rossi ◽

...

Keyword(s):

Management Strategies ◽

Spontaneous Remission ◽

Wine Quality ◽

Wine Production ◽

Flavescence Dorée ◽

Infection Pressure ◽

Scaphoideus Titanus ◽

High Infection ◽

Sensory Analyses ◽

Grapevine Disease

Flavescence dorée (FD) is a quarantine grapevine disease caused by a phytoplasma transmitted by the leafhopper Scaphoideus titanus Ball. FD management relies on compulsory insecticide treatments, roguing of infected plants, and substitution with certified material. Some grapevine cultivars show a spontaneous remission of symptoms (recovery). To determine if recovery is a suitable strategy to co-exist with disease in areas of strong infestation, the qualitative aspects of grapes, musts, and wines obtained from recovered Barbera and Chardonnay grapevines were investigated in two productive vineyards. Following field observations, about 1500 plants in each vineyard were divided into healthy (asymptomatic and negative in phytoplasma molecular diagnosis) and recovered (asymptomatic the year of observation but infected the year before). Maturation curves and microvinification tests followed by oenological and sensory analyses showed that maturation trends of recovered grapes were in line with those from healthy plants and the final qualities of wines were comparable. The spread of FD has strongly increased in Piedmont (Italy) in recent decades. Management strategies to cope with the disease are necessary to preserve traditional wine production. Despite the yield from recovered grapevines is quantitatively lower than that from healthy ones, we showed here that the wine quality is, however, preserved.

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