REDUCTION OF CHROMOSOME PAIRING BY A SPONTANEOUS MUTATION ON CHROMOSOMAL ARM 5DL OF TRITICUM AESTIVUM

Abstract

In a plant of T, aestivum L. and Thell. cv. Chinese Spring which was disomic for a mutant isochromosome of the long arm of chromosome 5D (di-isosomic 5DLm), partial chromosome asynapsis was detected at meiosis. Chromosome pairing in F1 hybrids form crosses of T. aestivum plants carrying the mutant isochromosome with Secale cereale, an intermediate pairing line of T. longissimum and with T. sharonensis disclosed that 5DLm carried a gene that reduced homoeologous chromosome pairing. This gene, designated Ph3 is less potent than its assumed homoeoallele on chromosomal arm 5BL, i.e., Phl. The possibility of Phl being transferred from 5BL to 5DL through homoeologous chromosome pairing and recombination was discarded. Rather, it seems more likely that this allele resulted from a spontaneous mutation of the pairing-promoter allele known to be located on 5DL.