The 2012 ASHS Annual Conference

High-quality water supply is often limited to gardening and landscaping in many regions of the world. Soil salinity is exacerbated due to irrigation with low quality water. A greenhouse study was conducted to evaluate six garden rose cultivars (‘Caldwell Pink’, ‘Marie Pavie’, ‘New Dawn’, ‘The Fairy’, ‘Knock Out’, and ‘Carefree Delight’) in response to salt stress. Plants grown in 5.7-L containers with a peat-based substrate were subjected to three salinity levels, 1.5 (control), 4.0 and 8.0 dS∙m^-1 electrical conductivity (EC) (moderate and high salinity levels). The salt solutions were prepared by adding sodium chloride (NaCl) and calcium chloride (CaCl₂) at 2:1 molar ratio to nutrient solution containing 125 mg∙L^-1 15 N–2.2 P–12.4 K. At moderate and high salinity levels, shoot growth decreased in all cultivars with the exception of ‘New Dawn’, and with ‘Marie Pavie’ and ‘Caldwell Pink’ having the greatest growth reductions (69% and 68%, respectively) at 8.0 dS∙m^-1 EC. Flower numbers decreased at high and moderate salinity levels in all cultivars except ‘New Dawn’ and ‘Knock Out’. In ‘The Fairy’, ‘Marie Pavie’, and ‘Knock Out’, no differences were found in leaf conductance between 1.5 and 4.0 dS∙m^-1 EC, and it was reduced at 8.0 dS∙m^-1 EC in all cultivars. ‘Caldwell Pink’ and ‘The Fairy’ had greatest reductions in leaf conductance at 8.0 dS∙m^-1 EC, followed by ‘Marie Pavie’, ‘New Dawn’, ‘Carefree Delight’, and ‘Knock Out’. Chlorophyll fluorescence decreased as salt level increased, which was lowest in ‘Caldwell Pink’. The six rose cultivars responded differently to elevated salinity, and ‘New Dawn’ was considered to be more tolerant to salt stress compared to the other five cultivars with its least reductions in shoot growth and flower numbers and highest chlorophyll fluorescence.