Structure of chromosome 5A of wheat speltoid mutants induced by the gametocidal genes of Aegilops speltoides

Abstract

Speltoid spikes occur when the dose of Q, (suppressor of speltoidy) located on the long (q) arm of chromosome 5A, decreases from the normal two to one or none. In crossed or selfed progeny of wheat lines that carry the gametocidal genes, Gc1a or Gc1b, 35 speltoid mutants appeared independently. The nature of the mutants, whether due to gene mutation or due to chromosome deletion, including the Q gene, was investigated. The mutants in the M1 generation were self-pollinated and segregation of the character in the M2 was observed. Speltoid plants in the M2 were crossed with ditelosomic 5AL (20II + tII), and pairing between the telosome 5AL and the chromosome that caused speltoidy was observed. Of the 25 lines that were analyzed by the two methods, 22 had a chromosome deletion on the long arm of chromosome 5A, the length of which was variable. The chromosome with deletion could be classified into at least three groups by comparison with the length of telo-univalent 5AL. In the M3 generation, six homozygous deletion lines were selected. Chromosome breakage that resulted in the deletions could be due to the involvement of a transposable element or a restriction – modification system.Key words: Triticum aestivum, Aegilops speltoides, gametocidal gene, chromosome breakage, mutation.