CHARACTERIZATION OF AVOCADO NURSE SEED SIZE AND SEEDLING DEVELOPMENT IN CV. ESTHER

Abstract

Avocado (Persea americana Mill.) propagation by etiolation and layering requires nurse seeds that generate homogeneous plantlets, capable of attaining the minimum diameter required for grafting in the shortest time. Seed size is often used as selection criterion. This study characterized three groups of seeds sorted by fresh weight, in the cv. Esther; the correlation between fruit and seed fresh weights was determined; and the effect of seed fresh weight on seedling growth was evaluated. The research was conducted in the 2009 and 2013 seasons. In 2009, 120 randomly selected seeds were sorted into three classes: small (28 to 43 g), medium (44 to 59 g) and large (60 to 75 g), and their physical traits (diameter, perimeter and embryo axis fresh weight) were compared. In both seasons, 90 fruits and their seeds were weighed, and both fresh weights were correlated; also 45 seeds were separated by their weights in the above mentioned categories and sown in a heated greenhouse (mean temperature 28 ± 5 ºC). Periods required for plumule emergence and for the stems to reach 4.5 mm in diameter and 20 cm stem length were registered. Large seeds showed higher diameter, perimeter and embryo axis fresh weight than small seeds. In both seasons a positive correlation between fruit and seed sizes was determined, although no effect of seed fresh weight over seedling growth rate was found.