Brosimum alicastrum: sexing, flower, seed production and growth regulators

Abstract

Brosimum alicastrum Swarts (known locally as ramón) is a tropical forest species with importance for the food sector; therefore, studying its physio-technical characteristics is essential. The sex ratio was determined in three adult populations of the state of Yucatán, Mexico. The first plantation comprised a total of 312 individuals, 208 males and 104 females: the second, 45 male and 29 female trees (74 trees) and the third, 41 males and 29 females (70 trees). On average, 64% of the trees were male and 34% female. In a separate plantation (50 trees) established ad hoc, 30% of the trees began to produce flowers 7 years after transplantation, 38% did so after 8 years, 28% at nine years and 4% at 10 years, 33 (66%) of the trees were males and 17 (34%) females. The experiment lasted from 2009 to 2019 and no sex changes were recorded during this time. The average seed production of adult trees was 145.6 kg tree-1 year-1. A parallel experiment was conducted to monitor retention of leaves, they remained in the crown for more than 40 months (1 217 days). Additionally, the content of plant growth regulators that could be used as molecular markers to select females was measured. Female trees showed higher content of gibberellic acid and cytokinins than male trees. The difference in cytokinin content between the sexes reached 500%. The relevance of these results for the establishment of commercial plantations is discussed.