Fruit Set in Avocado: Pollen Limitation, Pollen Load Size, and Selective Fruit Abortion

Abstract

Avocado is a woody perennial fruit crop originating in Central America and Mexico domesticated and cultivated in the Americas since pre-Columbian times, currently cultivated in subtropical, tropical, and Mediterranean climates worldwide, with increasing importance in international trade. Avocado shows an exuberant flower production that, however, results in a very low fruit set reflected in a massive abscission of flowers and fruitlets. Several factors are involved in this behavior, and, in this work, we have focused on pollination limitation. The results obtained show that pollen deposition takes place at the female and male stages during the avocado flowering season and that the percentage of flowers with pollen on the stigma varies along the flowering season, probably due to changes in temperature that affect not only the floral behavior but also pollinator activity. However, no embryo or endosperm development took place when pollination occurred during the male flowering phase. Thus, the low number of pollen grains landing on the stigmas of female stage flowers observed under natural pollination conditions might not be enough to ensure a good yield. The production of an excess of flowers and subsequent flower drop of most of the flowers provides the opportunity of a selective fruitlet drop depending on the genotype of the embryo since fruits derived from outcrossing showed higher chances of reaching maturity. Moreover, an important competition for resources occurs among developing fruits and new vegetative growth, conferring importance to the time of flower fertilization for effective fruit set.

Macroscopic and microscopic study on floral biology and pollination of Cinnamomum verum Blume (Sri Lankan)

“…Flies are one of the most abundant insects detected in the pollinator profile of cinnamon. In avocado, which has a similar type of floral biology, it has been identified that the thrips (Frankliniella and Thrips palmi) play a key role in pollination [37][38][39]. They are common visitors of cinnamon flowers during bloom [40].…”

Canopy-cooling systems applied on avocado trees to mitigate heatwaves damages

“…Despite its abundant flowering, Hass yield is low because of excessive flower and fruit abscission 40 . This abscission has many causes; some are internal due to the nutritional and physiological status of the tree 41 , some are related to the source of the pollen (self vs. cross) 42 and some are related to external abiotic stresses 43 . Drought and heat are known to be major negative factors in this context, exacerbating immature fruit drop 43 .…”

Boron Effects on Fruit Set, Yield, Quality and Paternity of Macadamia

“…Tree crops contribute over 600 million tons of the 10,600 million tons of annual global food production [3][4][5], and fruit number and fruit size are key components of tree crop yield [6][7][8]. Tree yields can be constrained by the percentage of flowers that are pollinated and fertilised, the percentage of fruit that develop to maturity, and the mass of the fruit components that contribute to yield [9][10][11][12]. Mass-flowering trees, which include many of the world's tropical and subtropical tree crops, typically produce many more flowers than mature fruit [9,[13][14][15].…”