Abnormal Development of Flower Bud and Fruit in Strawberry

—Factors Affecting Deformed or Malfunctioning Floral Organs and Fruit—

Abstract

Strawberries grown under low nitrogen during floral transition develop a normal dichasial cyme. However, in ‘Ai-Berry’, the shoot apical meristem flattens and develops into fasciated inflorescences when floral transition is suppressed by rich nitrogen and high temperatures in early autumn. In greenhouses, the fertility of pistils and pollen decreases for various reasons, but normal and well-shaped fruit production can be achieved by introducing pollinators. When a flower bud develops under excessive nitrogen, the number of rows (whorls) of pistils on the receptacle increases, so the occurrence of “catfaced berries” and “tip-green (white) berries” increases in ‘Ai-Berry’. In addition, if vegetative growth becomes too vigorous due to excessive fertilization or GA₃ treatment, boron and/or calcium translocation to the flower buds is suppressed, and “abnormal flowers” in ‘Hokowase’, “poorly fertilized berries” in ‘Tochiotome’, and “tip-shrunk berries” in ‘Sagahonoka’ develop along with tip burn of newly emerging leaves and sepals. The greening of pistils (“phyllody”) is caused by mycoplasma infection, similar to hydrangea, but another symptom of phyllody, transformation to sepal-like organs, is not caused by mycoplasma, but by high temperature during pistil differentiation. It is considered that “seedy” is caused by insufficient translocation of boron during fruit enlargement, and “tip softening” is caused by a lack of photosynthate during fruit ripening.