Screening methods for drought resistance in Rosa

Drought stress severely impacts plant production worldwide and is predicted to increasingly affect crop production due to climate change. The challenges presented hereby require solutions fitting in a sustainable and modern horticulture. One of the main strategies to cope with the changing environment is the development of new cultivars with an improved resistance against drought
stress. This study aims at applying polyploidy in this process, through the comparison of drought stress resistance in diploid Rosa genotypes, originating from a cross between R. ‘Yesterday’ x R. wichurana, and their mitotically induced tetraploid counterparts. The first step in this research is the development of adequate screening methods for the characterisation of the diploid segregating
rose population. After a first broad screening (69 F1-hybrids), based on ecophysiological parameters including relative water content and leaf water potential, we selected a drought tolerant and a drought sensitive diploid genotype. These genotypes were then subjected to two different irrigation
regimes, reducing the amount of water received by the drought stress group to less than 10% of the optimal amount given in the control group. Substrate volumetric water content, stomatal resistance and leaf water potential were monitored during the experiment. Biochemical analyses on leaf material
included osmotic potential, soluble sugar content, proline content, total antioxidant content, total protein content and enzyme (CAT, GPX, APX, SOD) activity. Results showed that both the drought sensitive and tolerant genotypes responded to drought stress with increased stomatal resistance, a more negative leaf water potential and accumulation of protein, soluble sugars and proline. In the control group we also noticed higher initial proline levels in the drought sensitive genotype. Sucrose and proline content and specific catalase activity during drought stress allowed a clear distinction between both levels of drought tolerance in this experiment. In further experiments, diploids and tetraploids will be compared.