Preliminary works on varietal selection for resistance to Xylella

Abstract

At the beginning of 2024, an outbreak of Xylella fastidiosa subsp. fastidiosa (Xff), ranked among the twenty priority pests, was intercepted on Vitis vinifera in Apulia (Cornara et al., 2025), well-known to be the causal agent of Pierce’s Disease (PD) of grapevine in California (Hopkins & Purcell, 2002). Given the high susceptibility of V. vinifera cultivars and the absence of genetic traits associated with theresistance to the bacterium, genetic improvement programmes should be activated at European level to develop resistant grape germplasm. The aim of this research is to analyse sources of resistance within the Vitis genus in order to plan a crossbreeding programme, supplemented by phenotypic selection protocols, for the introgression of resistance genes into V. vinifera plants.

Therefore, to address this aim, a systematic review of the literature publicly available, was carried out to identify American speciespotentially resistant to the pathogen. Indeed, the co-evolution with the pathogen has led native American species to develop resistance traits. Sources of resistance were found not only in V. arizonica, but also in V. berlandieri, V. × champinii, V. aestivalis, V. rotundifolia, V. vulpina, V. mustangensis, V. shuttleworthii, V. popenoei and V. nesbittiana (Dimaglie et al., 2025).

In 2024, a breeding programme was launched involving crosses between male plants obtained from Vitis arizonica seeds (by openpollination) and female-flowering of bunch grape cultivars Lambrusco di sorbara, Picolit, Moscato rosa and Kharistvala tetri. At the same time, the susceptibility of V. arizonica genotypes, used as parents, was investigated by artificially inoculating plants with bacterialsuspension and monitoring the progression of the infection. Preliminary data on the response to infection of V. arizonica genotypes indicate a variable and differential behaviour, spanning from plants with milder symptoms to ones completely dead over a 6-monthsobservation period.

The first filial generation (F1), resulting from the first crosses, comprises 256 hybrids and iscurrently undergone the phenotypic characterisation for selection for backcrossing. Future prospects include the evaluation of resistance to X. fastidiosa in the new obtained populations and the use of additional Vitis species in the breeding programme, in order to broaden the genetic base useful for the selection of resistant materials.

References

Cornara, D., Boscia, D., D’Attoma, G., Digiaro, M., Ligorio, A. M., Loconsole, G., … & Saponari, M. (2025). An integrated strategy for pathogen surveillance unveiled Xylella fastidiosa ST1 outbreak in hidden agricultural compartments in the Apulia region (Southern Italy). European Journal of Plant Pathology, 171(2), 277-285.

Hopkins, D. L., & Purcell, A. H. (2002). Xylella fastidiosa: cause of Pierce’s disease of grapevine and other emergent diseases. Plant disease, 86(10), 1056-1066.

Dimaglie, M., Ripa, C., Accogli, R. A., Di Sansebastiano, G.-P., Aprile, A., Rossetti, G., & Rustioni, L. (2025). Which American Wild Species Could Be Used in Grapevine Breeding Programs? AReview. Environments, 12(11), 402. https://doi.org/10.3390/environments12110402