Foliar Spray of Rice Rinsed Water to Tropical High Elevation Grown Strawberry (Fragaria ananassa Duch.) Increased Sugar Content of Ripe Fruits

Abstract

High air temperatures coupled with low light intensity, especially during the last two weeks of fruit ripening, may cause a low sugar content of ripe fruits of high altitude grown strawberry (Fragaria ananassa Duch.) in the tropics. An experiment in a plastic house was conducted to examine the effects of two week leaf spray, of rice rinsed water (RRW) containing carbohydrates on sugar content of ripe fruits. Preliminary investigation to measure the size of stomata opening in leaves of strawberry, the size of starch cells and the sugar and starch content in RRW of five varieties of rice, were also conducted. The main experiment in a plastic house, consisted of spraying to fruiting strawberry, five concentrations of RRW viz. 0, 5, 10, 15 and 20 ml l-1, once a day at 9.00 – 10.00 p.m. Treatments were replicated six times in a randomized complete block design. Rice rinsed water (1.0 g rice: 2.0 ml water) from C4 variety of rice contained 778.9 and 1494.7 μg ml-1sugars and starch, respectively. Stomata opening was 20.25 x 9.36 μm, was larger than starch cells size of   6.0 x 8.1 μm. Average minimum and maximum temperatures during the experiment were 15.0 and 25.8°C, respectively. No foliar disorder was observed resulting from the spray. Soluble solid content (SSC) of ripe fruits in plants receiving 10 ml l-1 leaf spray was 5.6%, increased (P = 0.05) 26.08% compared to control 4.6%, while sugars content increased 56.08% from 21135  to 32978 μg g-1 fresh weight. Further increased in concentration of RRW had no effect on SSC and sugar content of fruits. Relationships between concentrations of RRW with SSC and sugar content (μg g-1 fresh fruits) were quadratic.