Do ploidy levels play a role in (a)biotic stress resistance in roses?

Polyploidy is known to arise spontaneously in many plant species in nature. Frequently increased chromosome copies are associated with changes in plant anatomy and morphology. In addition, altered stress resistances in polyploids have been reported in ecological studies and in some agricultural crops. Nevertheless knowledge on the effect of polyploidy on stress resistance is limited. In our study rose is used as model crop to get better insight in the effects of chromosome doubling on both biotic(powdery mildew) and abiotic (drought) stress resistance. Mitotic polyploidisation of diploid roses isused to evaluate the influence of more genomic copies excluding the influence of
extra allelic diversity. A diploid population (90 genotypes) resulting from the hybridisation of ‘Yesterday’ x Rosa wichurana is used. In a first step the progeny was characterized for both drought and powdery mildew resistance. Subsequently, 19 F1-hybrids and both parents were selected for chromosome doubling. Genotypes were either susceptible or tolerant for drought and/or powdery mildew. Mitotic polyploidisation was obtained using an oryzalin(5 µM) treatment in liquid medium on nodal sections of tissue cultured plantlets.
Polyploidisation resulted in the first polyploid roses. Currently experiments to compare stress resistance at the diploid and tetraploid level are started. Preliminary results on the effect of ploidy level on plant morphology and on stress resistance in the selected rose genotypes will be given.