December 4, 2018

Enhancing Nature with a Little Nurture: A History of Avocado Breeding

Written by CTP Student Jessica Fostvedt

An ancient civilisation located in the south of what is now Mexico, the early Mesoamericans cultivated one of the most nutritious foods found on Earth.  The substantial value of this natural gift was not lost on them either.  In fact, avocados were a highly revered source of nourishment, thought to bestow strength and vitality.  It was only a small miracle that these early tribes were able to have such a wholesome fruit, since the giant ground sloths responsible for seed distribution went extinct thousands of years earlier.3

So, the early American tribes saved them from extinction, but how did avocados escape the New World and become a familiar addition to the modern diet worldwide?  For its introduction to Europe, the fruit was first described in a 1526 book by Martin Fernandez De Encisco.3  This was an important step in turning a tropical novelty into the modern commercial crop we recognise today, but the full process would take years of careful breeding…and some luck.

Tree breeding in general is a time consuming process, given the nature of the organism, but avocados in particular add an extra layer of challenge into the mix with their unique sexuality.  Like many plants, the avocado tree prevents self-pollination of its own flowers.  However, instead of simply separating male and female flowers, the avocado flowers have both sets of sexual organs, and expose them separately depending on the time of day.  For a ‘Type A’ tree, the female sexual organs open in the morning, while the male parts stay retracted and do not shed pollen.  The female parts then shrivel and die, while the male parts emerge the next afternoon and shed pollen.2  A ‘Type B’ tree opens its female parts in the afternoon and its male parts the next morning.  Performing cross pollinations by hand is naturally very difficult for this tree.  Breeders often just plant suitable trees within close proximity and hope for the best.

By sheer fortune, the best did come in the year 1926.  Rudolph Hass, a surname with which all avocado fans should be familiar, stumbled upon a chance product of the pollination lottery in a seed he purchased from an avocado nursery.  He intended to use the resulting tree to graft a Fuerte variety, but the new tree rejected his grafts and instead produced a strange new avocado.  In a few short decades the rich, nutty flavour of the Hass avocado outcompeted the once popular green-skinned Fuerte, and became the number one cultivar worldwide.1

The consistent flavour produced by grafting is great for consumers, but poses a challenge for the fate of avocados.  All commercial cultivars are genetically identical, and grafted onto disease-resistant rootstock when creating a new commercial tree.  To bring about real genetic change in the avocado industry, it will take more trials, many years, and some luck to take the next step forward.  Also, breeding must focus on more than just superior flavour and marketability.  A sustainable industry requires trees which use less water, hearty and disease resistant rootstock, and varieties that can face the more demanding climate challenges of our changing world.  The trend toward better environmental stewardship will ensure the most economical and highest quality fruit can be grown all over the world.  The expectations are high, but for a tree that emerged as a result of so many little miracles, it only needs a chance.

  1. “” Avocados From Mexico,
  2. “Growing Avocados: Flowering, Pollination and Fruit Set.” Agriculture and Food, Government of Western Australia,
  3. “The Origin Of Avocado: A Brief And Interesting History.” CureJoy, 13 Apr. 2018,