Outcrossing Rates in Annatto Determined by Sequence‐Related Amplified Polymorphism

Several methodologies have been proposed to accelerate breeding programs in annatto (Bixa orellana L.). However, before implementing them it is important to understand the mating system in annatto, a tropical species that is highly commercial for its unique capability to produce bixin. This report focuses on estimating outcrossing rates in an open‐pollinated population of B. orellana by sequence‐related amplified polymorphism (SRAP). Eleven open‐pollinated progeny arrays of 10 individuals each were used for this determination. Sequence‐related amplified polymorphism data indicated a multilocus outcrossing rate (tm) of 0.748 and an average single‐locus outcrossing rate (ts) of 0.651. Outcrossing was predominant in the B. orelllana open‐pollinated population. The multilocus estimates differed from the single‐locus estimates (0.097), suggesting the existence of mating among relatives (biparental inbreeding). A Wright's fixation index (F) of 0.332, indicated high homozygosity in the progeny evaluated with random mating, suggesting low variability. Furthermore, we found that based on experimental analysis, a minimum of 40 markers was required to obtain tm estimates that stabilized at approximately 0.7, and did not change significantly with an increasing number of markers. The molecular markers SRAP detect adequate levels of polymorphism in B. orellana for evaluating the mating system of this species.