| Effects of radiation on the susceptibility of wheat
seedlings to leaf rust K. KATSUYA National Institute of Genetics, Misima, Japan In Triticum Spelta, T. vulgare and T. Timopheevi a batch of seedlings with 2 leaves was irradiated by X-rays and gamma-rays at 10, 30, 50 and 70 kr. The seedlings were inoculated 1 day and 7 days after irradiation by spraying with an aqueous uredospore suspension (Puccinia triticina 21 B) and the effects of radiation on the susceptibility to leaf rust were observed. In the remaining seedlings of the same age the first and second leaves were cut off and the amounts of amino-nitrogen and reducing sugar were measured. Effects of irradiation on leaf characters, namely stomata size, internal structure and viability, and sporulation capacity on irradiated leaves were examined. Rust susceptibility of irradiated plants (T. Spelta and T. vulgare) was increased, as compared with the normals. In T. Timopheevi that was inoculated 7 days after irradiation, the third leaf was susceptible, while the first and second leaves of the same plants were mostly resistant. In T. Timopheevi seedlings, the amount of amino-nitrogen increased in the seedlings 1 day after irradiation, as compared with that of the normals, while it decreased 7 days after irradiation. The amount of reducing sugar increased in seedlings 1 day and 7 days after irradiation in comparison with the normals. Stomata size and internal structure of irradiated plants (T. Spelta and T. vulgare) did not change noticeably, as compared with the normals. Effects of irradiation on the viability of leaves were tested ; when the growing point suffered radiation damage, the already developed leaves remained longer fresh than those of the normals. The redosori of leaf rust on irradiated T. vulgare were larger than on normal plants. Relationships between rust susceptibility and radiation await further experiments. |