Carbohydrate and boron content of styles of 'Hass' avocado (Persea americana Mill.) flowers at anthesis can affect final fruit set

- New methods developed to quantify carbohydrate and boron in avocado styles.
- Carbohydrates were higher in avocado styles from ovaries that successfully set fruit.
- Boron content of styles was limiting for fruit set when soil boron content was low.

Avocado trees (Persea americana Mill.) invest heavily in flowering but fruit set percentage is unusually low, even after hand pollination. Our hypothesis was that the carbohydrate and boron content of avocado flowers at anthesis affected the potential of these flowers to set fruit. We hand pollinated 'Hass' avocado flowers in orchards in New Zealand and Spain, then 24 h later, after pollen tube growth had occurred, collected the styles from these flowers leaving the ovary intact. The excised styles were then analysed for starch, total and individual sugars and boron content. These data were later compared with the fate of the flower from which the style had been collected. Starch and all individual sugars were higher in the styles from flowers that went on to successful fruit set. Boron content was significantly higher in the styles from flowers that successfully set fruit in New Zealand but no significant difference was observed in the boron content of styles from Spain. These data support previous findings that suggest sink strength of flowers is predetermined at anthesis and influences the probability of fruit set for that flower.