Divergência genética, adaptabilidade e estabilidade e ganhos de seleção para caracteres agroindustriais de genótipos de guaranazeiro

Abstract

Guarana is an Amazon plant that has great economic potential due their antioxidant, energy and medicinal properties attributed to methylxanthines and polyphenols, being used as functional foods, cosmetics, soft drinks, food and energy industries. The knowledge of the behavior of guaraná genotypes in different environments aim to assist the breeding programs in the search for genotypes with higher contents of methylxanthines and phenolics compounds, associated with productivity. This study aimed to estimate the genetic relationships to select guaraná genotypes with desirable attributes in relation to agroindustrial characters in three locations in the State of Amazonas. Nine characters were evaluated in 8 genotypes established in three different sites along two years. The theobromine, caffeine, theophylline, catechin and epicatechin contents were quantified in extracts of mature seeds of guarana by High Performance Liquid Chromatography (HPLC). Each metabolite yield was calculated in function of dry seeds mass. Genetic variability was assessed by analysis of variance and Tukey's mean test, the dissimilarity by Mean Euclidean Distance, the dendrogram by Mean Linkage between Groups (UPGMA) and genetic correlation. Were evaluated analysis of variance, genotype x environment interaction, phenotypic correlations, the REML / BLUP analysis, the mean and variance components, adaptability and stability, classification of guaraná contents and typology, genetic values and selection index of Mulamba- Rank. Mature seeds have high levels of catechin, epicatechin, caffeine, lower theobromine values. Caffeine metabolism appears to be more stable in guarana than in other species. More productive plants tend to have higher caffeine and catechin contents. In the dendrogram there were two groups and six subgroups. Methylxanthines and phenolics can be used as descriptors for diversity studies in guaraná. The genotypes were classified into three commercial groups: "energetic and antioxidant" (CIR815, CIR904, CMA498), "antioxidant" (BRS Maués, CMU874) and "energetic" (CMA831 and CMU952, BRS-CG372). The genotypes CIR815 and CIR904 are potential future commercial cultivars of guaraná. The crosses with interesting characteristics to be explored in the genetic improvement program of guaraná, such as variability, in the search for higher levels of methylxanthines and phenolics are proposed, such as: CIR815 x BRS Maués, BRS Maués x CIR904, BRS-CG372 x CIR815, BRS-CG372 x CIR904 and BRS Maués x BRS-CG372. The genotypes with high adaptability and stability and greater gains were the cultivar BRS Maués, CIR815, CIR904, and CMU874 that being potential commercial cultivars. The caffeine, catechin, epicatechin, seed productivity and caffeine, catechin and epicatechin productivities are highly influenced by the environment. The accumulation of caffeine is higher at high temperatures and thermal amplitude, catechin and epicatechin vary according to annual precipitation, theobromine has very low environmental influence and high genetic influence. The productivities of dried seeds, caffeine, catechin and epicatechin are parameters that can be used for the selection of guaranazeiros genotypes.