Caracterização da variabilidade genética, sistema de cruzamento e parâmetros de germinação e emergência de euterpe precatoria martius em populações do Baixo Rio Solimões

Abstract

The assaí-da-mata (Euterpe precatoria Martius) is the most abundant and widely distributed Amazonian palm. It is economically, socially and environmentally relevant in the region because of its fruits and palm hearts used by traditional populations, and as a source of income, with growing demand for "Assai wine" beyond Amazonia that is attracting the interest of producers and entrepreneurs for its cultivation. Genetic improvement can contribute to increased fruit yield, using genetically selected seed plants directly in natural populations to maintain genetic variability, minimize inbreeding and prevent genetic erosion. Selection will be a key to the species’ cropping systems adopted by farmers, especially in the case of natural population enrichment. Despite the importance of assai for the State of Amazonas, little is known about the species. This species has no off-shoots and propagation occurs exclusively by seed. Due to restricted information and the importance of the species for the region, the objectives of this study were to: i) characterize the genetic diversity and spatial genetic structure; ii) determine outcrossing rates; iii) assess the percentage of germination and emergence, mean emergence time (MET), and emergence velocity index (EVI) and the relationship of the EVI with the observed heterozygosity (Ho). To achieve our goals ten microsatellite markers (transferred from E. edulis) were used to characterize the mating system, levels of genetic diversity and spatial genetic structure of populations of the municipalities of Codajás, Manacapuru and Manaquiri, along the lower Solimões River, State Amazonas, Brazil. Plant material was collected from 63 mature palms and 30 seed plants, from each of which 20 seedlings were analyzed. In the populations of Manacapuru and Manaquiri fruits were also collected from 30 progenies to determine germination rates. For germination, the experimental design was completely randomized, with four replications of 25 seeds and 30 treatments (progenies). For the mating system, the estimated outcrossing rates were high (tm = 0.96), although significantly less than one, indicating that some selfing occurred. The outcrossing rates among related individuals were substantial (tm - ts = 0.133), indicating that families have biparental inbreeding, as well as endogamy originated by selfing. Genetic diversity was high for adult palms and seedling progenies of all populations (Codajás: Â = 41 and 52, Ho = 0.48 and 0.47 and He = 0.49 and 0.51; Manacapuru: Â = 34 and 40, Ho = 0.49 and 0.42 and He = 0.49 and 0.45; Manaquiri: Â = 39 and 41, Ho = 0.48 and 0.50 and He = 0.51 and 0.48, respectively). The genetic differentiation between populations was moderate, estimated with Fst (0.143) and Gst (0.146). The analysis of coancestry between individuals by distance classes showed positive values for distance classes up to 53 km, suggesting that gene flow is restricted among the three populations due to isolation by distance. Great variability was found for all germination parameters, which was expected for a non-domesticated species, with germination percentages ranging between 8 and 98, with a mean of 69 %, percentage of emergency between 7 and 97, with a mean of 61 %, TEM between 29 and 100 days, with a mean of 69 days, and EVI from 0.11 to 1.80, with a mean of 0.93. The observed heterozygosity (Ho) showed a positive correlation with the seedling EVI in the Manaquiri population, but not the Manacapuru population. This study provides important genetic information for seed collection for breeding and conservation programs, as well as for the production of seedlings for planting.