| Effect of radioactive cobalt on characters of some
wheat varieties Hosni A. MOHAMED, A. M. OMAR and Mosa El BARAHAMTOUSHY Bahtim Exp. Station and Faculty of Agriculture, Ain Shams University Cairo, U. A. R. In 1960, dry seeds of Tosson, Giza 144. Giza 150 (Triticum vulgare), Baladi Bahtim (T. durum), Baladi 116 (T. pyramidale) and Einkorn (T. monococcum) were exposed to Co60 at the Exhibition of the American Atomic Energy Establishment in Cairo. Doses were 5000 r, 10000 r, 20000 r, and 30000 r. Treated seeds and untreated seeds were planted at the Bahtim Experiment Station both under greenhouse and field conditions. In the field studies, treatments were randomized and each treatment was replicated 4 times. Under greenhouse conditions, it was found that seedling emergence was delayed by radiation effect; differences between treatments were significant at 1% level. The delay was proportional with radiation dose. Also germination percentage, in general, decreased with the increase of the radiation dose. In studying plant height, lower doses of 5000 r and 10000 r generally activate seedling length while higher doses had a diminishing effect. In the field, studies were conducted during the growing seasons 1960 / 61 (R1) and 1961 / 62 (R2). Seedling emergence was delayed by radiation effect which agreed with results obtained in the greenhouse. None of the treated seeds of the two wheat varieties, Giza 144 and Baladi 116 germinated under field conditions while very few seeds of these two wheat varieties germinated under green house conditions. Further notes were recorded periodically each week in R1 only and indicated that percentage of seedling survival decreased with the increase in radiation dose. In case of Einkorn, seedling survival was favored by lower doses of radiation i. e. 5000 r and 10000 r. For adult plant characters, it was found that the increase of radiation dose was accompanied by an increase in the heading period, and consequently the heading was delayed. Also, radiation was found to affect number of ears per plant, number of spikelets per ear, number of grains per ear, seed set per spikelet and grain yield per plant. Infection with stem rust also increased with the increase of radiation dose, with the exception of the variety Einkorn in which it decreased. Characters such as plant height, number of tillers per plant, ear length and grain weight (weight of 100 seeds) were not affected by radiation both in R1 and R2. In R2 (season of 1961/62), some macromutations were observed and selected. These mutations were: 1. a tipped awned ear from Tosson (an awned wheat variety) isolated from the 30000 r treatment, 2. erected ears mutant from Tosson, selected from the 30000 r treatment, 3. slender straw from Tosson, isolated from the 20000 r treatment, 4. delayed ear emergence mutant from Tosson isolated from the 20000 r treatment, 5. long ear mutant from Baladi Bahtim isolated from the 20000 r treatment, 6. compacted ears from Giza 150 isolated from the 30000 r treatment and 7. short straw from Einkorn isolated from the 10000 r treatment. These mutants were studied during the seasons 1961/62, 62/63 and 63/64. Descendants of the tipped awned ear mutant from Tosson seemed to be of economic value as certain plants in the R4 were resistant to one or more of the 3 wheat rusts ( The parent Tosson is susceptible to the 3 wheat rusts). Few other plants were resistant to the 3 rusts. Most of these plants were awned. Some will be included in the wheat breeding program at the Bahtim Agricultural Experiment Station. |