Development of Botrytis cinerea Pers. ex Fr. on leaves of common poinsettia [Euphorbia pulcherrima Willd.]

The development of Botrytis cinerea was assessed on six cultivars of common poinsettia, differing in the colour of bracts, and being in great demand among buyers of these ornamental plants. Resistance to this pathogen differed in the investigated poinsettias. Cultivar ‘Malibu Red’ (red bracts) turned out to be most susceptible, while cv. ‘Marblestar’ (cream-pink) and cv. ‘Coco White’ (white) - relatively resistant to this fungus. After application of various inoculation methods (leaf discs, cut off leaves, whole plants) the differences in resistance to B. cinerea were confirmed for two extreme cultivars - susceptible (‘Malibu Red’) and resistant (‘Coco White’), which indicated genetic background of this polymorphism. The rate of disease development on poinsettia leaves was affected by the amount of spores used for inoculation (optimum density of 3.5·10⁵ B. cinerea conidia / ml suspension) and the addition of stimulants (0.1 M glucose with 0.05 M KH₂ PO₄), which facilitated germination and infection of the host tissue. The inoculated poinsettia leaves showed high stability of plasma membranes. In the susceptible cultivar, in spite of the development of necrotic spots, a significant increase in the membrane damage index (by 13%) was found only on day 7 of the disease development.Oceniano rozwój Botrytis cinerea na sześciu odmianach wilczomlecza pięknego, różniących się barwą przykwiatków, a cieszących się dużym zainteresowaniem u nabywców tych roślin ozdobnych. Stwierdzono zróżnicowanie stopnia odporności badanych odmian poinsecji na patogen. Odmiana ‘Malibu Red’ (czerwone przykwiatki) okazała się najbardziej podatna, a odmiany ‘Marblestar’ (kremowo-różowa) i ‘Coco White’ (biała) - względnie odporne na grzyb. Po zastosowaniu różnych sposobów inokulacji roślin (krążki liściowe, odcięte liście, całe rośliny) uzyskano potwierdzenie zróżnicowanej odporności na B. cinerea dla dwóch skrajnych odmian - podatnej (‘Malibu Red’) i odpornej (‘Coco White’), co wskazuje na podłoże genetyczne tego polimorfizmu. Na tempo rozwoju choroby na liściach poinsecji miała wpływ liczba zarodników wziętych do inokulacji (optymalna gęstość 3,5·10⁵ konidiów B. cinerea / ml zawiesiny) oraz dodatek stymulatorów (0,1 M glukoza z 0,05 M KH₂PO₄), które ułatwiały kiełkowanie i zasiedlanie tkanki gospodarza. Inokulowane liście poinsecji wykazywały wysoką stabilność błon cytoplazmatycznych. U odmiany podatnej, mimo rozwoju plam chorobowych, istotny wzrost indeksu uszkodzenia błon (o 13%) odnotowano dopiero w 7. dniu rozwoju choroby

The Effects of Pharmacological Carbonic Anhydrase Suppression on Defence Responses of Potato Leaves To Phytophthora Infestans

SUMMARY In this study we proposed carbonic anhydrase (CA) as an important element of basal resistance during the potato (Solanum tuberosum L.)-Phytophthora infestans interaction. We found a different β-CA expression pattern in incompatible vs. compatible systems correlated in time with CA enzyme activity. Resistant potato leaves supplied with dorzolamide (an inhibitor of carbonate CA activity) and challenged with the pathogen showed an elevated nitric oxide (NO) synthesis, which was the most evident during the early phase of NO burst (at 3 hpi) during hypersensitive response (HR). In vitro application of dorzolamide and effective inhibitors of NO synthesis confi rmed the implication of CA activity in NO metabolism during potato defense. To clarify how suppression of CA carbonate activity translates into the complexity of NO-related responses leading to potato resistance or susceptibility to an oomycete pathogen we analysed expression of NPR, PR1, and PAL. Taken together, pharmacological damping of CA activity revealed a functional link between CA and NOdependent signaling in potato defense against P. infestans manifested by accelerated NO formation and a modifi ed salicylic acid defense pathway. The dorzolamide-mediated effective responses for basal resistance also delayed symptoms of late blight in the susceptible potato cultivar, without overcoming HR formation in the resistant one