ABSTRACT. The use of efficient breeding methods depends on knowledge of genetic control of traits to be improved. We estimated genetic parameters, selection gain, and genetic diversity in physic nut half-sib families, in order to provide information for breeding programs of this important biofuel species. The progeny test included 20 halfsib families in 4 blocks and 10 plants per plot. The mean progeny heritability values were: 50% for number of bunches, 47% for number of fruits, 35% for number of seeds, 6% for stem diameter, 26% for number of primary branches, 14% for number of secondary branches, 66% for plant height, and 25% for survival of the plants, demonstrating good potential for early selection in plant height, number of branches, and number of fruits per plant. In the analysis of genetic diversity, genotypes were divided into 4 groups. Genotypes 18, 19, 20, and 8 clustered together and presented the highest means for the vegetative characters and production. Lower means were observed in the 17, 12, 13, and 9 genotypes from the same group. We detected genetic variability in this population, with high heritability estimates and accuracy, demonstrating the possibility of obtaining genetic gains for vegetative characters and production at 24 months after planting.

ABSTRACT. Castor bean (Ricinus communis L.) is a tropical plant of great commercial interest and a potential source of biodiesel. The development of genetically improved cultivars with high amounts of oil in the seeds and low ricin toxicity is crucial to increase the productivity of this crop. The use of TRAP (target region amplification polymorphism) markers to develop elite lineages and study genetic divergence is fundamental to advance the genetic improvement of this species. The goal of this study was to evaluate the genetic divergence among 40 elite lineages of R. communis, which belong to the NBIO-UFRB Genetic Improvement Program, using TRAP markers involved in the biosynthesis of oil and ricin. Total DNA was extracted and quantified from the leaf tissue of the castor bean plants, and 70 TRAP combinations (fixed and arbitrary primers) were used to genotype the 40 lineages. Of the 580 fragments amplified, 335 were polymorphic (58%). The genetic dissimilarity among the lineages was calculated by the Jaccard dissimilarity index using the UPGMA grouping method. A dendrogram was generated, and four groups formed, showing divergence among the elite lineages that favors selection. The TRAP 2 K.S. Simões et al. Genetics and Molecular Research 16 (3): gmr16039776 molecular markers were efficient at characterizing the genetic variability among the lineages and, because TRAP markers are functional markers involved in the biosynthesis of oil and ricin, they are important when studying the association between a marker and a candidate gene.