Production of wheat varieties resistant to rusts with the use of radioactive cobalt

Hosni A. MOHAMED and Mouaa N. El BARHAMTOUSHY

Bahtim Experiment Station Cairo, U.A.R.

In earlier studies (1, 2), some mutants were observed in a wheat field raised from the seeds exposed to different doses of radioactive cobalt. Mutants were selected on basis of their morphological characters. The most interesting of these mutants was a tipped awned mutant from Tosson. This mutant was observed in the R₂ during the growing season 1961/62 in one of the seed plots previously exposed to 30,000r. Tosson was till last year a commercial wheat variety, it is an awned wheat variety susceptible to the three wheat rusts, namely the black stem rust, the orange rust and the yellow rust. Seeds of this plant were sown in the growing season of 1962/63 and each plant was harvested separately ; ten plants were selected and sown in the growing season 1963/64. Further selection was practiced during the next seasons. Planting was in the rust nursery and notes were recorded for the three rusts and agronomic characters. During the growing season, resistant plants were labelled.

Characters studied were the presence of awns and rust reaction. The tipped awned ear character was dominant and segregtion occurred in some of the progenies during the growing seasons but not thoroughly studied as a number of plants for each line was not enough to draw a decessive conclusion. Calculating the number in some of the plots during the 1963/64 growing season, it was 294 tipped awned plants and 90 awned plants which account to 3 : 1 ratio or one gene may be responsible for this character. X² value was 0.510 and the P value was 0.50-0.20.

The most interesting was segregation in rust reaction. As previously mentioned, the original wheat variety is susceptible to the three wheat rusts. Descendants of the grown plants were resistant to one or more of the three rusts and susceptible to the others. Certain of these progienies were only resistant to the stem rust, others resistant to the orange rust, still others resistant to the yellow rust and susceptible to the other two rusts. Also, other lines were resistant to two of the three rusts. In the third group, lines were segregating in their reaction to one or more of the three rusts. Selection in the field was confined to resistane to rusts, and some of the plants possess high resistance to the three rusts. Further studies on the selected plants were usually carried out in the laboratory. In this growing season (1967/68), four lines were included in a preliminary yield trial. Plants of these lines resemble the original parent with respect to all mophologic characters. However, they were all highly resistant to the three rusts.

References

( 1 ) MOHAMED, Hosni A., Abdel Aziz M. OMAR and Mousa N. El-BARHAMTOUSHY 1965 Effect of radioactive cobalt on wheat II. Induced mutations. Bahtim Experiment Station Tech. Bull. 79.

( 2 ) MOHAMED, Hosni A., Abdel Aziz M. OMAR and Mousa N. El-BARHAMTOUSHY 1965 Effect of radioactive cobalt on characters of some wheat varieties. Wheat Information Service Nos. 19-20 : 16-17.

(Received Jan. 15, 1968)