Abstract
ABSTRACT: Annatto (Bixa orellana L.) is an arboreal species domesticated in Amazonia from its wild ancestor (B. orellana var. urucurana). Bixin extracted from its orthodox seeds is a natural dye widely used in the food industry. This study evaluated methods to overcome seed dormancy and determine the germination potential, comparing domesticated and wild annatto populations. Seeds from two domesticated-type populations and two families of a wild-type population, stored for two years after field collection, were submitted to five treatments to overcome dormancy: T1 - control; T2 - mechanical scarification (with sandpaper); T3 - mechanical scarification (with sandpaper) + immersion in water at 36 ºC overnight (12 hours); T4 - immersion in water at room temperature (23 ºC, on average) for 24 h; T5 - immersion in concentrated sulfuric acid (95 - 98%) for 15 min + running water for 3 min. Highly significant differences (P < 0.001) were observed in the germination percentage of annatto seeds between wild and domesticated types, and among the treatments tested. Domesticated types showed higher germination percentage (10 - 58%) over all treatments when compared to the wild type (0 - 44%). The best treatments were those performed with mechanical scarification. Given the simplicity, we concluded that mechanical scarification with sandpaper is a good alternative to overcome dormancy of annatto seeds.
Highlights
Potencial de germinação e métodos de superação da dormência de sementes para populações domesticadas e selvagens de urucum após dois anos de armazenamento
No information is provided for annatto seeds in the Rules for Seed Analysis (BRASIL, 2009), the Instructions for Seed Analysis of Forest Species (BRASIL, 2013) provides information regarding B. orellana seed germination, where paper substrate is recommended, as well as a wide range of temperatures, from 20 to 35 oC
Several factors may explain the differences in germination between individuals and populations; considering that W1 and W2 came from the same wild population, we suggested an intrapopulational genetic difference in the germination of wild annatto seeds
Summary
Potencial de germinação e métodos de superação da dormência de sementes para populações domesticadas e selvagens de urucum após dois anos de armazenamento. To elucidate the dormancy mechanism of annatto seeds and evaluate the effect of different methods for overcoming dormancy, allied with different temperatures for germination, PICOLOTTO et al (2013) showed that scarification with sandpaper or sulfuric acid for five minutes, and temperatures of 25 oC or 20 - 30 oC are recommended for this species.
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