Этюды в области гибридизации, иммунитета и трансплантации растений

were put under glass covers, others—under two isolated layers of gauze (with intervals of 2—6 cm). , Besides, infection with Puccinia triticina and Puccinia gluma- rum was made by- simply .placing and fastening leaves with uredo­ spores into the leaves of the test plants. This latter means of infection is efficient, as a rule, since the mycelium of Puccinia hardly expand from the site of infection. If the plant is infected from top to bot­ tom, this should be explained by the great number of infection hearths. As control for Tr. fungicidum served in all the experiments: ^a) plants of the same kind without artificial infection, (b) plants of susceptible kinds, especially the wheat «Durable», belonging to Tr. vulgare (at early ages). The experiments were carried on for three years. The incuba­ tion period in the control plants differed greatly and derpended on the weather. We studied .microscopically the germination of uredospores on leaves, the formation of growth hyphae and the ari­ sing of appressories on the stomata. The hyphae, formed by the appres- sory cannot penetrate through the close stomata and especially through the cuticula. If the .epidermis is sectioned, infection takes place easily: The condition of the stomata on leaves and stems was verified seweral times during the day after the method of Busca- lioni, viz. the stomata were covered with a layer of collodium and served as document for microscopical examination. Early in the morning the stomata of all the wheat kinds are always open, infec­ tion is therefore made in the mornings, the time necessary for ger­ mination of the uredospores being taken into account besides. While the soft kinds of wheat (Durabl, Moscovskaia 2411, etc) showed breaks of epidermis and inset of reproduction 5—7— 12 days after infection, our new wheat species.Tr. fungicidum sho­ wed no signs of infection during three years of numerous experiments. This is so apparent and astonishing, that it is possible to regard this species of wheat as resistant to the three kinds of Puccinia. Infection with Ustilago tritici and Tilletia trijtici was carried on in another “series of experiments. The spores of these parasites were also placed in exciccators with calcium chloride. Dessicated chlamydospores preserve their germina­ tion capacity for several years.*At the season of infection we applied chilling of the spores, in order to raise their germination capacity. Dessicated spores of Ustilago tritici were blown by means of a small dry pipette onto the pollen of fertilized Tr. fungicidum flo­ rets by carefully moving asunder the paleas of the flowers. Not less than 20 flowers were infected, this operation was repeated on five parallel lots. The non-infected ears were removed. The grain obtained after infection was sown the following year into separate pots. All the grown plants gave a normal harvest and all the ears were healthy. This proves that when the florets were in ­ fected, the ovules did riot become infected and that the mycelium of Puccinia hardly expands from the infection site. For infection with T illetia tritici we prepared a soil extract in order to utilize the bios -■■42-».. Электронная Научная Сельскохозяйственная Библиотека