The value of gametoclonal variation in breeding for quantitative traits in flue-cured tobacco (Nicotiana tabacum L.)

Summary In tobacco (Nicotiana tabacum L.), anther-derived doubled haploid populations have been shown to exhibit large amounts of unexpected genetic variation and a severe depression in cured leaf yield when compared to conventionally inbred genotypes from comparable sources. A previous study had predicted that the yield depression observed in a doubled haploid population-derived from a near homozygous cultivar, NC95, might be overcome through a recurrent selection program. In the current study, progress from three cycles of full-sib family selection for improved yield in an anther-culture derived population of NC95 was measured, as well as the remaining genetic variation within the population. A design II experiment was conducted in the population following three cycles of selection. Results indicate that the NC95 yield level has been recovered in the third selection cycle population. Although most of the genetic variation in the population appears to be exhausted, the additive genetic variance among maternal half-sib families for yield is significant, and it appears that continued yield improvement can be made through recurrent selection. Significant additive-genetic variance for yield was found among maternal half-sib families but was essentially zero among the paternal half-sib families, suggesting that remaining genetic variation is not being transmitted through pollen. One possible explanation results from the phenomenon of DNA amplification that can occur during the anther culture process, and that may enable extraordinary recombinational events and reduce the viability of male gametes.