Temperatures after bloom affect plant growth and fruit quality of strawberry

Abstract

The influence of four day/night temperature combinations (18/12, 25/12, 25/22, 30/22) on plant growth and fruit quality of ‘Earliglow’ and ‘Kent’ strawberry ( Fragaria × ananassa Duch.) were studied. The optimum day/night temperatures for leaf and petiole growth was 25/12°C, while for roots and fruits it was at 18/12°C. For the growth of the whole plant, 25/12°C was also the optimum temperature. Fruit surface and flesh color became darker ( L* value decreased) and greater in pigment intensity (chroma value increased) as the day and night temperatures increased. Leaf color was brighter, greener and greater in pigment intensity as day and night temperatures decreased (18/12°C). Increased in growth temperatures resulted in decreased fruit quality including soluble solids (SSC), titratable acids (TA), SSC/TA ratio, and ascorbic acid (AA) content in the fruit. Plants grown at 18/12°C greatest amounts of fructose, glucose, and total carbohydrates in fruit and decreased with increasing temperature. The greatest fruit sucrose content occurred at 25/12°C and the lowest was at 30/22°C. Fruit from plants grown at 18/12°C also contained greater amounts of citric acid and ellagic acid, but lesser amounts of malic acid. As the day/night temperature increased, fruit malic acid content increased, while citric acid and ellagic acid content decreased. Temperatures of 30/22°C inhibited plant and fruit growth, and also reduced fruit quality. At higher day and night temperatures (25/22 and 30/22°C), leaves, petioles, and crowns had higher amounts of fructose and myo-inositol, whereas at cooler temperatures (18/12 and 25/12°C), greater amounts of sucrose were found. Plants grown at 25/12°C had the highest starch and total carbohydrate contents. Cooler day/night temperature (18/12°C) shifted biomass from leaves to roots.