Volume 56 Number 1 Article 9
Year 2002 Month 1
Title: High Temperature Effects on CO2 Assimilation Rate in Genotypes of Fragaria xananassa, F. chiloensis, and F. virginiana
Authors: S. Serce, P.W. Callow, H.-J. Ho, and J.F. Hancock
Abstract:
CO2 assimilation rates (A) in two Fragaria xananassa cultivars, ten native F. chiloensis genotypes,
and nine native F. virginiana genotypes were compared in growth chambers held at two day/night temperature regimes: 20/15°C and 30/25°C. Light intensity (PAR) was maintained at 500 µmol m-2 s-1 and
day lengths were held at 14 hours.
At 20/15°C, F. virginiana had significantly lower A (10.4 µmol CO2 m-2s-1) than either F. xananassa (11.6 µmol CO2 m-2 s-1)or F. chiloensis (11.7 µmol CO2 m-2 s-1). All
species showed a significant reduction in A at 30/25°C; however, F. virginiana dropped the least at 24%,
while F. xananassa fell 42% and F. chiloensis dropped 54%. 'Seascape' and 'Tribute' had intermediate
levels of A under cool temperatures (12.8 µmol CO2 m-2 s-1 and 10.4 µmol CO2 m-2 s-1) and their CO2
assimilation rates were reduced by 39-44% by high temperatures.
Several F. chiloensis genotypes had
higher A than the F. xananassa genotypes under cool temperatures, but they were more negatively effected by high temperatures.
In F. virginiana, LH 50-4 and RH 18 had A values comparable to 'Seascape'
and 'Tribute', and they showed more modest reduction in A at high temperatures (< 5%). These two
genotypes may be good parents to improve heat tolerance in cultivated day-neutral germplasm.
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