| "White scald" mutation in wheat A. T. PUGSLEY Agricultural Research Institute, Wagga Wagga, N.S.W., Australia Although huge seedling populations of wheat are under observation each year, very rarely are mutants reported. The occurrence of a recessive mutant in an F2 population from the cross Maguarovar 98 x Thew is of interest in that it has apparently not been recorded previously. Maguarovar 98 of Hungarian origin was obtained from the U. S. D. A. World Wheat Collection in 1952. Thew is a well known Australian variety. Both are resistant to mildew and the cross was made with a view to establish the identity of the gene for resistance in Maguarovar 98. No mildew susceptible segregates were detected in the F2 of 207 plants. However 5-6 days after germination a number of plants developtd unusual lesions on the first leaves. Ten days after germination there were 153 normal plants and 54 plants bearing lesions. The plants with lesions later grew quite normally and, with the unaffected plants, were grown on to produce, F3 seed. Progenies have been studied in F3, F4 and F5 and the evidence indicates that the "white scald" conditions is inherited as a simple recessive. Symptom expression of "white scald" varies considerably. Commonly the first leaves are affected although symptoms may not appear until the four leaf stage. In severe cases several leaves are scalded but on no occasion have affected plants been killed. Typically a transverse white scald-like band appears across the middle of the leaf, the distal portion bending over but remaining quite turgid and green. Sometimes two bands may appear on a single leaf and occasionally the lesion develops longitudinally. |