THE EFFECT OF PH GENE ALLELES ON SYNAPTONEMAL COMPLEX-FORMATION IN TRITICUM-AESTIVUMXT-KOTSCHYI HYBRIDS

Chromosome pairing at zygotene-pachytene was studied in Triticum aestivum .times. T. kotschyi hybrids (2n = 5x = 35, genomic constitution ABDCUSV) by electron microscopy of synaptonemal complexes in spread microsporocyte nuclei. Hybrids carrying either the Ph allele or the ph allele, which differ markedly in metaphase I pairing, are both capable of greater than 90% pachytene pairing, although pairing in the Ph hybrids appeared slower or less synchronised. In both genotypes branched synaptonemal complexes were formed by intra- and interchromosomal pairing. The Ph gene control on homoeologous pairing does not act on the ability to pair into synaptonemal complexes. It may act on the rate of pairing or the time of crossing over.