instruction: From the passage find the major production areas where Avocado is cultivated. Display the results in comma separated format.
context: The avocado (Persea americana) is a medium-sized, evergreen tree in the laurel family (Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for its large and unusually oily fruit. The tree likely originated in the highlands bridging south-central Mexico and Guatemala. Its fruit, sometimes also referred to as an alligator or avocado pear, is botanically a large berry containing a single large seed. Avocado trees are partly self-pollinating, and are often propagated through grafting to maintain consistent fruit output. Avocados are presently cultivated in the tropical and Mediterranean climates of many countries. Mexico is the world's leading producer of avocados as of 2020, supplying nearly 30% of the global harvest in that year.
  
  The fruit of domestic varieties have smooth, buttery, golden-green flesh when ripe. Depending on the cultivar, avocados have green, brown, purplish, or black skin, and may be pear-shaped, egg-shaped, or spherical. For commercial purposes the fruits are picked while unripe and ripened after harvesting. The nutrient density and extremely high fat content of avocado flesh are useful to a variety of cuisines and are often eaten to enrich vegetarian diets.
  
  In major production regions like Chile, Mexico and California the water demands of avocado farms place strain on local sources. Avocado production is also implicated in other externalities, including deforestation and human rights concerns associated with the partial control of their production in Mexico by organized crime. Global warming is expected to result in significant changes to the suitable growing zones for avocados, and place additional pressures on the locales in which they are produced due to heat waves and drought.
response: Chile, Mexico, California