Avocado is one of the most nutritious fruits that has originated in Central America. Avocado is now grown in most of the tropical and subtropical countries. The pulp of Avocado is buttery called as butter fruit, and the fruit has very high fat content and the sugar content is low.
Avocado starts bearing at 5-6 years after planting and has a marked tendency to biennial bearing which is prevalent in a number of other fruit trees.
But there is a specific problem with the fruit set as far as avocado is concerned. Avocados exhibit unique flowering behaviour that is influenced by temperature, particularly cold conditions affecting the extent of the fruit set.
In avocado, the inflorescence is a compound panicle. The individual flowers are morphologically bisexual having fertile male and female organs. But they exhibit dichogamy i.e. the male and female reproductive organs matured at different times thereby avoiding self pollination in individual flowers. In dichogamy, they are protogynous i.e. female reproductive organs come in maturity earlier than the male. The type of dichogamy in avocado is a complicated one unique to avocado – the diurnally synchronous dichogamy.
The flowers open and close twice over a two day period and each opening lasts for only half a day. The female parts of all flowers that open at a time in a particular tree will mature simultaneously and behave functionally as female flowers and similar goes with the male parts of all the flowers when the flowers open next time. Typically, all the open flowers on a single tree will be synchronized, it means they will all be either functionally male or female at the same time.
Furthermore, all the trees of a particular group will be exhibiting the same sex phase at a particular time and the opposite sex phase during the next opening of the same flower. So if the trees of a single group are planting, they would not set the fruit. Trees of two groups that are compatible with each other are required for the fruit setting.
Based on this unique flower behaviour, avocado cultivars are divided into two groups A and B.
In type A flowering sequence, the first opening of flower takes place in the morning and behaves as functionally female, closes and the second opening takes place during the afternoon the following day and behaves functionally male.
In type B flowering sequence, first they open in the afternoon, behave as functionally female and then second opening in the next morning, behave as functionally male.
Flower type | Day 1 (Morning) | Day 1 (Afternoon) | Day 2 (Morning) | Day 2 (Afternoon) |
A | female | closes | closes | male |
B | male | female | male | closes |
In the morning, the pistils of cultivar A are fertilized by Pollen of Type B cultivar, while during afternoon B-pistils are ready to receive A-pollen. 2-3 cultivars of avocado are planted in the same orchard in order to maintain sound pollination for fruiting in the avocado trees. A-type and B-type cultivars must be planted in the ratio 1:1 or 2:1 in an avocado orchard. Honeybee are the chief pollinating agents.
A-type cultivars : Hass, Gyun, Anaheim, Lab Dash Mexico, Pinkerton, Rincon
B-type cultivars : Fuerte, Bacon, Nabal, Novel, Shepard, Jutaune, Edranol, Ettinger