Author: Michael T. Clegg, Vanessa E. T. M. Ashworth, Haofeng Chen

Avocado breeding is challenged by the inability to perform controlled pollination, the long juvenility period of the trees (4–7 years) and their considerable size. Because of these difficulties, varietal improvement has long relied on multi-year field trials during which large numbers of seedlings are grown to maturity and screened for desirable (phenotypic) characteristics. Inferior trees are culled as their deficiencies become apparent, leaving only the most promising genotypes. Clearly, the time, land resource, and labor costs associated with growing trees to the appropriate stage of development are huge. This financial burden is further compounded by conventional breeding approaches that use open-pollination, which results in a complete reshuffling of genes—good and bad—in the hope of coming across a superior seedling. This approach happened to work well for Rudolph Hass who discovered such a chance seedling in his back yard, but Mr. Hass was a very lucky man indeed.

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