HIGH ROOT-ZONE TEMPERATURES INHIBIT GROWTH AND DEVELOPMENT OF FRAGARIA SPECIES

The influence of root-zone temperature on strawberry species has not b een thoroughly studied. Two experiments were conducted to determine th e effect of root-zone temperature on vegetative growth, runner number, runner plant development, and water relations in Fragaria chiloensis Duch., F. virginia Duch., and F. viridis Duch. In Experiment I, clones of F. chiloensis 'FRA 366' that originated in California, F. chiloens is 'FRA 606' (Alaska) F. virginiana 'FRA 67' (Maryland), and F. virgin iana 'FRA 104' (Wyoming) were grown hydroponically for 21 days with ro ot zones at 23, 29, or 35 degrees C. All clones with roots held at 35 degrees C had less fresh mass gain over time, fewer runners, fewer run ner plants, less leaf area on mother and runner plants, and less root dry mass than plants at 23 or 29 degrees C. Plants at 29 degrees C had less runner plant leaf area than plants at 23 degrees C. F. virginian a exhibited greater vegetative growth and produced mere runners and ru nner plants than F. chiloensis, but there were no species-temperature interactions. In Experiment II, F. chiloensis 'FRA 366' (mother plants originating in California) and F. viridis 'FRA 333' (Germany) were gr own hydroponically for 56 days with root zones at 23, 29, 35, 20/26 (n ight/day), 26/32, or 32/38 degrees C. F. viridis was more sensitive to high root-zone temperature than F. chiloensis, and most growth reduct ions were with reduced transpiration and leaf water potential. A low t emperature (23 degrees C) promoted maximum growth of F. viridis, where as exposure to root-zone temperatures as high as 32 degrees C fostered maximum growth of F. chiloensis.