Table 2_Genetic and physiological mechanisms of grapevine resistance to Xylella fastidiosa infection: a progressive acquisition of knowledge.xlsx

From the 1950s onward, systematic screening and breeding programs identified multiple heritable resistance sources in native southeastern American grape species. Genetic studies indicated that resistance could depend on the inheritance of dominant alleles at multiple loci, explaining the low frequency of resistant progeny in some crosses. These findings prompted breeding programs aimed at introgressing resistance into elite bunch-grape backgrounds while retaining desirable fruit-quality traits.

The identification of the bacterium “Xylella fastidiosa” as the causal agent of PD further facilitated screening and phenotyping through microscopy, serological and molecular assays, standardized inoculation protocols, and the combined evaluation of bacterial population size and symptom severity. A major advance was the identification of resistance in V. arizonica. Genetic mapping led to the discovery of the major resistance locus PdR1 and associated molecular markers, enabling marker-assisted selection and accelerating the elimination of susceptible seedlings during breeding.

More recently, transgenic approaches have complemented conventional breeding strategies. Overall, the available literature confirms the general susceptibility of V. vinifera to PD while highlighting the progressive enhancement of resistance through the exploitation of wild grape germplasm, conventional breeding, marker-assisted selection, and genetic engineering.</p>