Severe infestations of Daktulosphaeria vitifoliae on the hybrid rootstock 1103 Paulsen in Apulia Region (Italy)

Abstract

In the last four years, despite repeated fertilization and irrigation applications from the farmer, a progressive vegetative decline and yield decrease have been observed in a large (5 ha) 10-year-old table grapes vineyard of the cv. Autumn Pearl grafted on 1103 Paulsen and located nearby the Ionian Sea in Taranto province (Apulia, Italy). In autumn 2024, during a survey for verifying the status of the plants, an evident stunted vegetative growth, yellowing of the foliage and premature leaf fall were observed on about 80 % of the vines.

Preliminary sampling and nematological analyses were performed on the soil and on representative roots with galls resembling to root-knot nematodes. No nematodes were detected, both in the soil and on the roots.

Subsequent observation and analyses revealed the presence within the nodules of aphids. Individuals have been characterized both considering the morphological characters and using molecular markers at mitochondrial level by sequencing the gene COI (Cytochrome Oxidase Subunit I). The results of the analysis gave 100 % similarity with the Daktulosphaeria vitifoliae confirming the identification made on morphological bases.

To assess the extent and severity of the infestation on the roots, eight plants randomly distributed in the field were sampled and completely uprooted. Tuberosities were observed on 50 % of the observed roots. Nodosities and radicicolae forms occurred on all collected, prevalently secondary, grapevine roots. Mycological analysis was carried out and occasionally from the rotting roots infested by Phylloxera were isolated fungi pathogens, such as: Cylindrocarpon spp, Fusarium spp., Macrophomina sp., and Rhizoctonia solani.

In conclusion, the finding of severe knots on the roots of the hybris 1103 Paulsen was probably the main factor leading the vegetative and productive decline observed in the aerial parts of the plants, until to the final decision to uproot, during last winter, all the plants of the young vineyard affected by the problem. Further investigation is required in the area, to assess the extent and severity of the phenomenon, the factors that favoured this serious damage detected on the roots of the 1103 Paulsen, one of the most widespread rootstock in the southern European countries considered highly resistant to Phylloxera, the eventual presence of new aggressive Phylloxera biotypes, the starting of a surveillance program to prevent potential future dangerous scenarios for Mediterranean viticulture.