Hyperspectral mapping of the response of grapevine cultivars to Plasmopara viticola infection at the tissue scale

Abstract

Resistance of grapevine to Plasmopara viticola is associated to hypersensitive reaction, accumulation of stilbenoids, and formation of callose depositions. Spectral characterization of infected leaf tissue of cvs. ‘Regent’ and ‘Solaris’ with resistance genes Rpv 3-1 and Rpv 10 & Rpv 3-3, respectively, suggested that resistance is not depending on large-scale necrotization of host tissue. Reactions of the resistant cultivars and a reference susceptible to P. viticola were studied using hyperspectral imaging (range 400 to 1000 nm) at tissue level and microscopic techniques. Resistance of both cultivars was incomplete and allowed pathogen reproduction. Spectral vegetation indices characterized the host response to pathogen invasion; the vitality of infected and necrotic leaf tissue differed significantly. Resistance depended on local accumulation of polyphenols in response to haustorium formation and was more effective for cv. ‘Solaris’. Although hypersensitive reaction of some cells prevented colonization of palisade parenchyma, resistance was not associated with extensive necrotization of tissue and the biotrophic pathogen survived localized death of penetrated host cells. Hyperspectral imaging was suitable to characterize and differentiate the resistance reactions of grapevine cultivars by mapping of the cellular response to pathogen attack on tissue level and yields useful information on host-pathogen interactions.

Traditional and Emerging Approaches for Disease Management of Plasmopara viticola, Causal Agent of Downy Mildew of Grape

“…In resistant cultivars, which exhibit hypersensitive reactions, this results in a more rapid reduction of the photosynthetic rate than in susceptible cultivars, with susceptible cultivars exhibiting a reduction only after visible symptoms have appeared [37]. Resistant cultivars also exhibit stomatal closure and decreased transpiration as early as four days after inoculation [37], as well as increased production of anthocyanin-like compounds [38]. Increased production of H 2 O 2 has been observed within hours of inoculation and continuing for up to 3 days afterward in resistant cultivars [39,40]; this was correlated with earlier development of necrotic lesions [39].…”

“…Such lesions are the first visible indications of P. viticola infection and typically appear as pale green-to-yellow "oily" spots on the surfaces of the leaves (Figure 2a). These spots can expand to affect much of the surface of the leaves, particularly in cultivars that exhibit hypersensitive reactions [38], which can lead to premature defoliation in severely affected vines. Reduced photosynthetic rates and premature defoliation can negatively affect sugar accumulation in berries and overwintering buds, as well as delay berry ripening.…”

“…Many advances in modeling and detection technologies have occurred in recent years, giving growers options beyond traditional scouting. Some of these technologies utilize thermal imagining, hyperspectral imaging, and artificial intelligence [38,[48][49][50][51][52]. Such tools can support a more targeted approach to disease detections and fungicide application.…”