Biochemical and molecular analyses of potential markers for evaluating the competition for resources between mature fruit and open flowers in ‘Hass’ avocado trees

ABSTRACTAlternate bearing of ‘Hass’ avocado (Persea americana Mill.) trees is a phenomenon across avocado-growing regions around the world. In New Zealand, the cycle can be more complex as the fruit often remains on the trees for over 12 months, potentially resulting in competition for resources between fruit from the previous year and the flowers. This work looks at the impact of the presence of a 12-month-old heavy crop on the accumulation of boron and carbohydrates to flowers. By sequencing and measuring the expression of the avocado Trehalose Phosphate Synthesis (TPS1) gene, we report on the effects of cropping cycle on the delivery of carbohydrates to the flower. Differences in sugar delivery rate to the flower reflected by differences in TPS1 expression were not reflected in the carbohydrate and boron contents of open flowers, and it is suggested that flowers require a certain amount of sugars to accumulate to enable their development and to reach a stage where they are able to open as a female flower.