Fenologia, viabilidade do pólen, emergência de semente e conteúdo de DNA nuclear de açaizeiros (Euterpe spp.)

Abstract

Açaizeiros, Euterpe precatoria and Euterpe oleracea, are species of the Arecaceae family, distributed throughout the Amazon region. These palms have great socioeconomic value in the regions where they occur and are used for different purposes, such as food, cosmetics, oils and fibers. The characterization of its germplasm in terms of phenology, pollen viability and the establishment of seedlings will allow the advancement of breeding programs in Euterpe. The objectives of the research were to study the phenological events and the pollen viability of E. precatoria; the emergence of seedlings and the DNA content of E. precatoria, E. oleracea and their interspecific hybrids. The phenological events of E. precatoria were followed in 20 genotypes over a period of 12 months. For the study of pollen viability, pollen was collected in inflorescences from individuals of E. precatoria from the Experimental Station of Embrapa Amazônia Ocidental in Manaus. The ideal culture medium for the germination of pollen grains was determined and the percentage of germination was evaluated. Three dye solutions were also tested to determine pollen viability: Tetrazolium (0.1%), Cotton Blue (0.05%) and Trypan Blue (0.2%) and pollen viability was evaluated for 180 days. Seedling emergence and nuclear DNA content of E. precatoria and E. oleracea and their interspecific hybrids were also evaluated. Flowering was verified every month, with the peak occurring fom August to December. The fruiting period was recorded throughout the evaluation period, being more intense between September and May. The highest percentage of pollen germination occurred in the culture medium with 100 g L⁻¹ of sucrose and 300 mg L⁻¹ of Ca (NO₃) ₂ 4H₂O. With the use of the three dyes, the average viable pollen values were considered high (above 70%), facilitating the use of staining methods in the genetic improvement of the species. The pollen grains stored in the refrigerator (5°C), in the freezer (-20°C) and in the ultrafreezer (-80°C), remained viable until the 180 days were evaluated. It was observed that the seedlings of E. oleracea showed an Emergency Speed Index (ESI) ranging from 2.14 to 3.18, compared to E. precatoria that ranged from 0.62 to 1.03 and to interspecific hybrids that presented intermediate ESI, between 0.74 to 1.80. In general, the average DNA content of E. precatoria, E. oleracea and the interspecific hybrids were 7.52 pg, 6.17 pg and 6.95 pg, respectively. The best time to collect pollen from E. precatoria is between August and December. The pollen of this species has high viability (above 70%), even when stored for 180 days allowing for artificial hybridization for controlled crosses.