Plant & Animal Genome IX Conference

Workshop: Cotton
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MAPPING THE GOSSYPIUM G GENOME AND THE FATE OF G. AUSTRALE CHROMOSOMES IN G. HIRSUTUM X G. AUSTRALE ALIEN CHROMOSOME ADDITION LINES II: THE FIDELITY AND FREQUENCY OF G. AUSTRALE CHROMOSOME TRANSMISSION IN BACKCROSS PROGENY

Centre for Plant Biodiversity Research, CSIRO Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia

Hexaploid bridging is a means of facilitating recombination between homoeologous chromosomes that otherwise reside in diploid and tetraploid genomes. As chromosomes of the donor diploid species are gradually shed through repeated backcrossing to the tetraploid species, homoeologous interchanges can occur when the donor chromosomes, which lack a homologue, are involved in allosyndetic bivalents or multivalents with the target chromosomes. The extent of homoeologous introgression recovered is a function of the frequency of homoeologous interchanges relative to the rate of donor chromosome loss in each generation. Although cytological observations can estimate the frequency of allosyndetic chromosome associations, the genetic consequences of these events are difficult to decipher. Here 570 chromosome-specific EcoRI-MseI AFLP alleles were used to track the fate of the 13 G. australe chromosomes in 18 BC₁ and 110 BC₂ aneuploids and identify recombinant individuals. The 18 BC₁ and the 110 BC₂ aneuploids inherited 46% and 45%, respectively, of the available chromosomes. The number of chromosomes per BC₁ individual ranged from 2 to 8 (mean 6); the number of chromosomes per BC₂ individual ranged from 1 to 6 (mean 2.7). The frequency of chromosome transmission ranged from 11% to 72% of the BC individuals for Chromosomes A through L. Chromosome M occurred in all the BC₁ and BC₂ individuals. Seven of the G. australe chromosomes were involved in 13 putative recombination events. The genomic extent of these events was estimated using a genetic linkage map. Chromosomes A and F carry genes for brown lint and pink flower color, respectively.