Reproductive characterization and preliminary studies on controlled breeding of Annatto (Bixa orellana L.)

• Published in: Plant systematics and evolution 2012-01, Vol.298 (1), p.239-250
• Main Authors: Joseph, Nisha, Siril, E. A, Nair, G. M
• Format: Article
• Language: English
• Subjects: Annatto; Anthers; Biomedical and Life Sciences; Bixa orellana; Cost allocation; cross pollination; crossing; dehiscence; Flower stigma; flowers; fruit set; Fruits; genetic improvement; germination; Life Sciences; Original Article; parents; Plant Anatomy/Development; Plant breeding; Plant Ecology; Plant Sciences; Plant Systematics/Taxonomy/Biogeography; Plants; Pollen; resource allocation; Seeds; stamens; sucrose; trees; tropics; Viability
• ISSN: 0378-2697; 1615-6110
• DOI: 10.1007/s00606-011-0541-0

Annatto (Bixa orellana L.) is an important dye-yielding medium-sized tree occurring in the tropics. Investigations aimed at elucidating the reproductive characters as well as establishing a set of breeding parameters for genetic improvement of B. orellana was carried out. Records on pollen/ovule ratios of annatto showed that this species is xenogamous. The acetolyzed pollen of B. orellana was tricolporate. The fluorochromatic test showed 95% pollen viability. The viability of the pollen grains decreased sharply after 4 h from anther dehiscence. The optimum time range for artificial pollination was standardized between 12:00 and 13:00 h. A high in vitro germination rate (92%) of freshly collected pollen was recorded in modified Brewbaker’s medium with 15% sucrose. Resource allocation studies showed that the construction of each flower cost 1.162 g. The floral vegetative cost was 75%. Of the total allocation, 21% was spent by the stamens. Based on identified reproductive characters, controlled pollination experiments were conducted by selecting four morphologically distinct parent plants: (1) green-fruited with reddish spines, (2) red-fruited, (3) brown large-fruited, and (4) with brown distorted fruits. In artificial cross-pollination experiments, wide variation ranges in fruit set (0–95%) and fruit maturation (0–85%) were observed in different crosses. The number of seeds per capsule also showed variation (0–40 per capsule). Germination studies of seeds raised from different crosses showed a maximum 93% germination. The present study proved that improvement in B. orellana could be achieved by adopting breeding techniques using specifically selected parents.