[The dynamics of abscisic acid and cytokinins content in the leaves of wheat-aegilops lines and their parental forms affected by powdery mildew]. / Dinamika abstsizovoi kisloty i tsitokininov v list'iakh pshenichno-égilopsnykh linii i ikh roditel'skikh form pri porazhenii muchnistoi rosoi.

We studied the dynamics of abscisic acid and cytokinins content in wheat-aegilops lines and their parental forms affected by powdery mildew. Lines 95/99i and 56/99i demonstrated the types of resistance untypical of the soft wheat Rodina and Aegilops speltoides k-389 but typical of Ae. speltoides Tausch from other natural habitats. A relative stability of the hormonal balance in the course of the infection was demonstrated for lines 95/99i and Ae. speltoides k-389 highly resistant to the pathogen penetration. Line 56/99i was sensitive to the penetration; however, a subsequent prolonged hypersensitive response eliminated pathogen colonies surrounded by necrotic areas. A correlation between disbalanced hormonal metabolism of cytokinins and low resistance to the infection has been revealed for 56/99i line and Rodina cultivar. Free form of abscisic acid was revealed in the intact plants of the parental forms. Bound form of this hormone was revealed in the infected plants of lines 95/99i and 56/99i as well as of Ae. speltoides k-389, which seems to be a marker of their different stress resistance according to the phenotypic manifestation of powdery mildew.

[Morphological variability of the wheat powdery mildew in the context of its parasitic adaptation to the lines of wheat Aegilops with different resistance]. / Morfologicheskaia izmenchivost' vozbuditelia muchnistoi rosy pshenitsy v cviazi s ego paraziticheskoi adaptatsiei k razlichnym po ustoichivosti pshenichno-égilopsnym liniiam.

We studied the interaction between the pathogen and wheat-Aegilops lines with different resistance as well as their parental forms in the course of powdery mildew infection using scanning electron microscopy. Line 51/99i proved to be similar to the parental form, Rodina variety, by the infection progress. The both genotypes featured pronounced adhesion of the primary infection structures to the surface of the plant epidermal cells in addition to formation of large developed colonies of the fungus, which indicates the partners compatibility. Development of powdery mildew on line 135/99i was similar to that on the parental form Aegilops speltoides K-389. The interaction between the partners featured decelerated incubation period. Rare parasite colonies formed from mycelial hyphae with multiple hyphal lobes and usually disturbed adhesion to the surface of the epidermal cells were observed. Such pattern of the pathogen development points to the resistance factors in these plant hosts, mostly, at the level of pathogen penetration. The types of resistance of lines 95/99i and 56/99i were not specific for the parental form Ae. speltoides K-389 but rather for Ae. speltoides specimens from other natural ranges (Ryabchenko et al., 2002). This suggests that Ae. speltoides has a polygenic immune potential with the elements inheritable by the hybrids irrespective of the used resistance donor.

[Influence of phytohormones on development of conidial inoculum of causative agents of the phlox and barley powdery mildew]. / Vliianie fitogormonov na razvitie konidial'nogo inokuliuma vozbuditelei muchnistoi rosy floksa i iachmenia.

We studied the role of phytohormones: zeatin, kinetin, and abscisic acid, in the regulation of development of the conidial inoculum of Erysiphe cichoracearum DC. f. phlogis Jacz. and E. graminis DC. f. hordei Marchal. When the pathogen conidia were in direct contact with phytohormones, the intensity of their germination significantly increased. In the presence of cytokinins, the amount of normal appressoria decreased and that of abnormal growth tubes increased. On the phlox leaves treated with cytokinins, the intensity of germination of the conidia increased, as compared to the control, while abscisic acid exerted the opposite effect. The treatment of barley leaves with cytokinins did not affect markedly the development of conidial inoculum, as compared to the control, while abscisic acid significantly decreased the intensity of germination of the conidia. On the leaves of different Phlox species, the degree of germination of the conidial negative correlated with their resistance against the powdery mildew. The role of cytokinins in pathogenesis of biotrophic fungi is discussed.

[Characteristics of halo formation during pathogenesis as a response of cereal epidermal cells to penetration of powdery mildew pathogens]. / Osobennosti formirovaniia galo v protsesse patogeneza kak otvetnaia reaktsiia épidermal'nykh kletok zlakov na proniknovenie vozbuditelei muchnistoi rosy.

A cytophysiological study was carried out of the functional status of a halo as a response of the host plant to contact with a powdery mildew pathogen. Interactions of the powdery mildew causative agents with barley, wheat, wheat-wheat-grass hybrids, wheat-aegilops lines, and aegilops with different genotypic resistance lead to the expression of haloes during pathogens, which are induced by infection pegs of the primary growth tubes appressoria, and hyphal lobes. Haloes are visualized using cytochemical reactions to proteins and scanning electron microscopy. The observed differences in the size of haloes and intensity of their staining (uniform or zonal) are related, to a great extent, to individual reactions of the plant cell at the penetration site and, to a lesser extent, to the level of genotypic resistance. An analysis of electron microscopy and cytochemistry studies suggests that the halo as a physiologically active zone is localized at the level of the plant cell plasmalemma. Active taxis of the cell organelles to the site of infection during the formation of a halo suggests that some kind of informational signals to changes in the cell metabolism are spread from the halo zone, which lead to compatible or incompatible interactions.

[Level of cytokines, abscisic and salicylic acids in the leafs of Phlox under the effect of invasion by conidia of phytopathogens]. / Uroven' éndogennykh tsitokinov, abstsizovoi i salitsilovoi kislot v list'iakh floksa metel'chatogo i shilovidnogo pod bliianiem zarazheniia konidiiami fitopatogenov.

We studied the effects of the invasion of Phlox paniculata L. and Ph. setacea L. by causative agents of the phlox powdery mildew (compatible combination) and lupine powdery mildew (incompatible combination) on the level of endogenous cytokinins and abscisic and salicylic acids. In all experimental variants, the level of zeatin-riboside and abscisic and salicylic acids in the leaves of invaded plants increased within 48 h. The highest level of phytohormones and salicylic acid was recorded in the absolutely resistant species Ph. setacea.