A Fresh Look at Avocado Pollination

Abstract

The synchronously dichogamous flowering behavior of avocado has historically been assumed to promote cross-pollination. Preliminary studies in southern California have revealed that self-pollination is more typical. The primary objective of the California research is to determine the paternity of individual fruit sampled during early and late fruit development using SSR markers. Cultivars included Hass as the primary cultivar and Bacon, Ettinger, Fuerte, Harvest, Lamb Hass, Marvel, Nobel, SirPrize, and Zutano serving as cross-pollinizing cultivars. We were able to: 1) estimate proportions of self- and cross-pollinated `Hass' fruit with cultivars planted in rows of varying proximity to the `Hass' rows; determine if the proportion of outcrossed fruit increased during maturity due to preferential abscission of self-pollinated fruit; and 2) determine if there is preferential retention of fruit cross-pollinated by a specific cultivar during maturation. On average, cross-pollination by any individual cultivar in 2004 was 6% or less in marble-sized fruit. Over 70% of the fruit were self-pollinated. This is greater than the proportion of self-pollination (about 30%) observed in near-mature fruit harvested in the previous year, 2003. Proportions of marble-sized fruit pollinated by each cultivar within each row were compared to the proportions of self or cross-pollinations in fruit harvested from the same trees at near-maturity. We observed about a 10% increase in proportion of self-pollinated fruit and a concomitant decrease in retained fruit derived from cross-pollination. Self-pollination appears to be the dominant mode of pollination. These preliminary results indicate that trees benefit from it, perhaps in preference over cross-pollination.