The Durability of Quantitative Host Resistance and Variability in Pathogen Virulence in the Interaction Between European Grapevine Cultivars and Plasmopara viticola

Abstract

European grapevine, Vitis vinifera, carries no major resistances against Plasmopara viticola, the causal agent of grapevine downy mildew. The introgression of quantitative trait loci conferring resistance to P. viticola (Rpv) from American and Asian donor species has resulted in a range of resistant cultivars. In light of the perennial nature of grapevine and the high evolutionary potential of P. viticola, the durability of this quantitative resistance is an important challenge. Durability of host resistance and variability in pathogen virulence may be evaluated by describing interactions between pathogen isolates and grapevine cultivars in terms of Rpv loci. A set of 16 cultivars carrying different combinations of Rpv loci, was challenged with five P. viticola isolates, obtained from susceptible or Rpv3.1+V. vinifera cultivars. Based on the severity of sporulation, different host and pathogen phenotypes might be distinguished, which could be related to the presence of different Rpv loci. The hormonal responses before and during some interactions were compared to assess the resistance mechanisms underlying Rpv3.1, Rpv10, and Rpv12 and the infection mechanisms of the different isolates. This paper reports on the strength of some of the commonly used Rpv loci, single or stacked. The isolates derived from Rpv3.1+ hosts, GREPv1 and GPHPv1, were able to sporulate intensely on cultivars carrying Rpv3.1, without triggering necrosis. Moreover, Rpv10 was not able to efficiently halt the development of the Rpv3.1-breaking isolate GPHPv1. Cultivars carrying Rpv12, however, were resistant to all five P. viticola isolates. Phytohormones might be implicated in the basal resistance against this pathogen, but during the early defense response, no significant hormonal responses to the isolates were observed. The isolate-specificity of the Rpv3- and Rpv10-mediated resistance suggests that these loci do not result in the most sustainable resistance. Furthermore, the isolate-specific behavior of the pathogen emphasizes the need for a characterization system for P. viticola. A standardized phenotyping assay may be used to determine P. viticola pathogen phenotypes or measure the durability, strength, and isolate-specificity of the host quantitative resistances. The characterization of both components of the pathosystem may lead to an increased understanding of the resistance mechanisms, beneficial for a durable deployment of resistance genes.

Phenotyping for QTL identification: A case study of resistance to Plasmopara viticola and Erysiphe necator in grapevine

“…Environmental conditions may cause host stress-induced resistance and reduced DM and PM infections. For instance, temperatures below 8°C (Moyer et al, 2010 ), nutrient deficiency (Keller et al, 2003 ), and drought (Heyman et al, 2021 ) reduce the development and susceptibility of grapevine organs to diseases, delaying epidemics (Moyer et al, 2016 ). In addition, cultural strategies (soil tillage and fertilization) and stimulated grapevine growth increase both leaf and berry susceptibility to pathogens (Fernandes de Oliveira et al, 2021 ).…”

“…Selective pressures, such as fungicide treatments (Frenkel et al, 2015 ; Delmas et al, 2017 ; Santos et al, 2020 ; Massi et al, 2021 ) and host resistance, are responsible for changes in population biology over time. In Europe, extensive asexual reproduction and mutation rates of P. viticola , despite little genetic differentiation, yield virulent isolates on Rpv3.1 (Peressotti et al, 2010 ; Venuti et al, 2013 ; Delmotte et al, 2014 ), Rpv10 (Heyman et al, 2021 ), and Rpv12 (Wingerter et al, 2021 ) grapevine genotypes. Similarly, phenotyping data in North America suggest the selection of natural virulent E. necator isolates on Ren2 (Cadle-Davidson et al, 2016 ) and Run1 (Feechan et al, 2015 ) grapevine genotypes.…”

Studies on the resistance of different developmental stages in susceptible and tolerant grapevine cultivars against the pathogen Plasmopara viticola

“…It is difficult to say whether these findings can be applied to other PIWI cultivars with the same Rpv loci combination, as certainly not all resistance loci have been fully identified in all PIWIs. Furthermore, there seem to be qualitative differences in one and the same resistance locus Heyman et al (2021). demonstrated for Rpv 3.1 that cultivars carrying this locus show a different strength of resistance response.…”

“…However, the resistance of PIWI cultivars cannot be attributed to stomata changes alone. Rather, defense responses, for example, through the formation of stilbenes or hypersensitive reactions, are crucial(Eisenmann et al, 2019;Gindro et al, 2012;Heyman et al, 2021).In addition, inflorescence and grape experiments have shown that PIWI cultivars have different levels of resistance at different stages of development. PIWI cultivars with two resistance loci have higher resistance than S. Girs, which carries only one resistance locus.…”

Transcriptional Profiling of Resistant and Susceptible Cultivars of Grapevine (Vitis L.) Reveals Hypersensitive Responses to Plasmopara viticola

“…The degree of symptoms mainly varies with the surrounding environment and the resistance of the host grapevine ( Atak et al, 2017 ; Frobel and Zyprian, 2019 ; Weitbrecht et al, 2021 ). Many studies demonstrated that different varieties of grapevine process different levels of resistance and susceptibility to downy mildew ( Gomez-Zeledon et al, 2013 ; Zhang et al, 2017 ; Zhao et al, 2019 ; Heyman et al, 2021 ). Therefore, cultivating high-quality disease-resistant Vitis varieties is the best choice for sustainable viticulture.…”