Abstract
Fire blight represents a widespread disease in Lilium spp. and is caused by the necrotrophic Ascomycete Botrytis elliptica. There are >100 Lilium species that fall into distinct phylogenetic groups and these have been used to generate the contemporary commercial genotypes. It is known among lily breeders and growers that different groups of lilies differ in susceptibility to fire blight, but the genetic basis and mechanisms of susceptibility to fire blight are unresolved. The aim of this study was to quantify differences in fire blight susceptibility between plant genotypes and differences in virulence between fungal isolates. To this end we inoculated, in four biological replicates over 2 years, a set of 12 B. elliptica isolates on a panel of 18 lily genotypes representing seven Lilium hybrid groups. A wide spectrum of variation in symptom severity was observed in different isolate-genotype combinations. There was a good correlation between the lesion diameters on leaves and flowers of the Lilium genotypes, although the flowers generally showed faster expanding lesions. It was earlier postulated that B. elliptica pathogenicity on lily is conferred by secreted proteins that induce programmed cell death in lily cells. We selected two aggressive isolates and one mild isolate and collected culture filtrate (CF) samples to compare the cell death inducing activity of their secreted compounds in lily. After leaf infiltration of the CFs, variation was observed in cell death responses between the diverse lilies. The severity of cell death responses upon infiltration of the fungal CF observed among the diverse Lilium hybrid groups correlated well to their fire blight susceptibility. These results support the hypothesis that susceptibility to fire blight in lily is mediated by their sensitivity to B. elliptica effector proteins in a quantitative manner. Cell death-inducing proteins may provide an attractive tool to predict fire blight susceptibility in lily breeding programs.
Highlights
Since the dawn of time, lily (Lilium spp., Liliaceae, L.) represents one of the most prestigious ornamental flowering plants in the Occidental culture as it was considered the symbol of divine purity
To assess the susceptibility of lily genotypes to B. elliptica and the virulence of B. elliptica isolates in a quantitative manner, we inoculated 12 fungal isolates (Table 2) on leaves of 18 lily genotypes (Table 1) representing three hybrid groups (Asiatic, Longiflorum and Oriental) and four intersectional hybrid groups (LA, Longiflorum × Oriental (LO), Oriental × Asiatic (OA), Oriental × Trumpet (OT))
Genotypes belonging to the hybrid groups A, Longiflorum × Asiatic (LA), and OA showed significantly more severe symptoms than genotypes of hybrid groups L, O, LO, and OT upon inoculation with all B. elliptica isolates tested (Figures 1, 2, 4, 5)
Summary
Since the dawn of time, lily (Lilium spp., Liliaceae, L.) represents one of the most prestigious ornamental flowering plants in the Occidental culture as it was considered the symbol of divine purity. The genus Lilium consists of approximately 120 described species (Angiosperm Phylogeny Group (APG), 2020). The assortment of commercial lily genotypes includes thousands of hybrids that were generated via intrasectional crosses between different Lilium species and these have been divided into four hybrid groups: Asiatic (A), Longiflorum (L), Trumpet (T), and Oriental (O). To combine ornamental traits and obtain more vigorous plants, a variety of intersectional hybrids were subsequently generated using artificial pollination, embryo rescue and polyploidization techniques (van Tuyl et al, 1991; Lim et al, 2008; van Tuyl and Arens, 2011), resulting in the interspecific hybrid groups LA (Longiflorum-Asiatic), LO (LongiflorumOriental), OA (Oriental-Asiatic) and OT (Oriental-Trumpet). Breeding efforts have far predominantly focused on ornamental traits and to lesser extent on the resistance to pests and pathogens. Given the current challenges more focus on disease resistance is needed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
