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Pathogenicity and ultrastructural studies of mode of penetration by Phoma strasseri in peppermint stems and rhizomes

100%

Zimowska B.

nr 4

Pathogenicity and ultrastructural investigation of the inoculation of peppermint stems and rhizomes with Phoma strasseri conidia was undertaken using scanning and transmission electron microscopy to examine the host-parasite relationship. Pathogenicity experiments demonstrated that all tested P. strasseri isolates had infected the stems and rhizomes of peppermint. Of all inoculation methods, direct placement of colonized agar plugs on damaged epidermis and soaking stems and rhizomes in conidial suspension were the most e#ective. !e behavior of the conidia deposited on the stems and rhizomes was investigated at different time intervals after inoculation: 6, 16, 24, 36 and 48 h. Conidia produced an appressorium directly at the end of a short germ tube. Appressoria were formed over the cuticle, but never over stomata. Direct penetration to host tissue through the cuticle was observed. The spore and hyphae were covered with a mucilaginous sheath.

Effect of abscisic acid and ontogenic phases of the host alga on the infection process in the pathosystem Scenedesmus acutus - Phlyctidium scenedesmi

100%

Pouneva I. D.

nr 5

The parasite contamination make difficult laboratory cultivation of green algae and decrease significantly the production of microalgal biomass during industrial cultivation. In the present study the influence of the endogenous abscisic acid content (determinate by gas chromatography) on the host-parasite relationship in different ontogenetic phases of the host Scenedesmus as well as resistance induction after treatment of synchronous algal culture with ABA were studied. Synchronization of algae was carried out by alteration of light and dark periods. The age groups under study were: autospores (at the beginning of the light period), growing cells, mature cells (belonging to in the end of the light period) and mature cells, starting to release autospore at the beginning of dark phases. The higher levels of endogenous ABA during the algal autospore formation as well as exogenous ABA supply of (10-5 M) inhibited the infection process in the pathosystem green microalga Scenedesmus acutus and unicellular fungal parasite Phlyctidium scenedesmi. The treatment with fluridone 10-7 M (an inhibitor ofABA biosynthesis) increased the host susceptibiltty during all ontogenetic phases. The susceptibiltty of S. acutus to the chytridial infection depended on the endogenous ABA level during different ontogenetic stages of the alga.

Pathogenicity and ultrastructural studies of the mode of penetration by Phyllosticta plantaginis in ribwort leaves

88%

Zimowska B.

tom 13

nr 3

Pathogenicity and ultrastructural investigation of the ribwort leaves inoculated with Phyllosticta plantaginis conidia was undertaken using scanning electron microscopy to examine the host-parasite relationship. Pathogenicity experiments demonstrated that all tested P. plantaginis isolates had infected leaves of ribwort. Of all inoculation methods, direct placement of colonized agar plugs on damaged epidermis and soaking leaves in conidial suspension were the most effective. The behavior of the conidia deposited on the leaves was investigated at different time intervals after inoculation: 7, 18, 25, 48 and 72 h. An appressorium appeared directly at the end of a short germ tube grown from conidia. Appressoria were formed over the cuticle in some distance from the stomata. Penetration through the stomata was observed.

W pracy podjęto badania nad spełnieniem postulatów Kocha dla pięciu izolatów Phyllosticta plantaginis oraz ultrastrukturą inokulowanych liści babki w celu wyjaśnienia powinowactwa pomiędzy P. plantaginis a rośliną żywicielską. Badania wykazały, że wszystkie testowane izolaty spowodowały infekcję na inokulowanych liściach babki. Z trzech uwzględnianych w badaniach metod inokulacji, najbardziej efektywnymi okazały się metoda polegająca na umieszczaniu krążków pożywki przerośniętej przez grzybnię na zranionej tkance liścia oraz metoda uwzględniająca zanurzenie liści w zawiesinie zarodników konidialnych. Obserwacje ultrastruktury inokulowanych liści babki prowadzono w mikroskopie skaningowym po 7, 18, 25, 48 oraz 72 godzinach. Wykazały one tworzenie się appresorium na końcu strzępki kiełkowej oraz wnikanie patogenu przez aparaty szparkowe.