Volume 56 Number 1 Article 9 Pages: 57-62
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
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 Ámol m-2 s-1 and
day lengths were held at 14 hours.
At 20/15░C, F. virginiana had significantly lower A (10.4 Ámol CO2 m-2s-1) than either F. xananassa (11.6 Ámol CO2 m-2 s-1)or F. chiloensis (11.7 Ámol 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 Ámol CO2 m-2 s-1 and 10.4 Ámol 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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