Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 6/1/2005
Citation: Li, Y.H., Windham, M.T., Trigiano, R.N., Fare, D.C., Spiers, J.M., Copes, W.E. 2005. Components of resistance to powdery mildew in flowering dogwood. Phytopathology. 95:S60.
Technical Abstract: Spore germination, infection structure formation, and colony development of Erysiphe pulchra, the causal agent of powdery mildew of dogwood, were examined on glass slides and leaf disks of a susceptible flowering dogwood line using light and scanning electron microscopy. On both glass slides and leaf disks, conidia germinated within 2 h after inoculation (hai). One to four germ tubes grew from two poles of a conidium, one or two of the germ tubes formed initial appressoria, and only one of the germ tubes with initial appressoria formed secondary appressoria. However, formation of initial and secondary appressoria was delayed on glass slides (48 and 72 hai, respectively) compared to that on dogwood leaf disks (3 and 24 hai, respectively). Branched hyphae did not grow from germinated conidia on glass slides. However, on dogwood leaf disks, branched hyphae were observed 48 hai. In epidermal cells, the fungus formed compact and globose haustoria. Conidia formation on conidiophores started on leaf disks 7 days after inoculation. Conidia germinated and formed initial and secondary appressoria on glass slides without establishing a parasitic relationship, but food sources in conidia could not provide enough energy and nutrition for growth of branched hyphae.