GENETICS SOCIETY OF CANADA AWARD OF EXCELLENCE LECTURE AN INDUCED MUTANT WITH HOMOEOLOGOUS PAIRING IN COMMON WHEAT

Abstract

An apparent deletion of Ph, the chromosome-5B suppressor of homoeologous pairing, was obtained by X-raying normal pollen and using it on plants monosomic for a 5B chromosome carrying the marker Hairy-Neck, previously transferred from rye. Of the 1278 M 1 offspring, 675 were eliminated without test, because they were either 1) hairy necked and therefore possessing a maternal 5B that would have hidden any deficiencies present in the X-rayed 5B; 2) nullisomic in appearance and thus likely to have a badly damaged 5B; or 3) completely or nearly male sterile, which precluded the recovery homozygous of any mutant that might have been present. A total of 438 M 1 plants were tested for pairing mutations, mostly by crossing to Triticum kotschyi and looking for increased pairing. Only one mutation was obtained that appears to be a deficiency of Ph. The homozygous mutant is somewhat reduced in vigor and fertility, and male transmission from the heterozygote was only 38.6%. A second mutation, which leads to an intermediate level of homoeologous pairing, is not located on chromosome 5B.