Stem Rust Resistant Variants in Irradiated Populations Mutations or Field Hybrids?¹

Abstract

Synopsis The relatively large number of rust‐resistant mutants observed in the N2 coming from N1 plants not isolated in the Aberdeen nursery were not true Markton phenotype and it is suggested they are the result of field hybridization. There were no rust‐resistant mutants in the N2 population grown from isolated N1 plants.

Induction of mutations for rust resistance in wheat

“…It would hence be premature to classify the mutant as a dominant one. CALDECOTT et al (1959) have already shown that mutations for stem rust resistance in species of Avena and Triticum are rare in radiation experiments and that the high frequency of mutations reported by KONZAK (1956) is not realised when the M1 plants are grown in isolation. KONZAK (1959) as well as COOPER and GREGORY (1960) have, however, found in carefully planned experiments that mutations for disease resistance do occur in irradiated material but at a very low frequency.…”

Radiation‐Induced Mutations for Stem Rust Resistance in Oats1

“…Hence, this ratio which suggests dominance may not necessarily reflect the true genetic situation. 3 The offspring of this plant also varied considerably for a number of characters including growth habit, height, form, maturity, and seed type (too many for any possible hybrid). Such variation is probably due to unusual chromosomal recombinations or to duplications and deficiences associated with the induced sterility.…”

Mutations and Crop Improvement. V. Arachis Hypogaea L. (Leguminosae)

“…On the contrary, the yielding ability of some resistant mutants exceeds that of the control. COOPER and GREGORY also compared their resull s to those obtained by CALDECOTT et al (1959) in oats. The latter authors found no resistant mutant in 1740 N, plants.…”