Bioestímulo da microalga Chlorella sp. na produção de mudas de Pitaya

Abstract

The production of pitaya seedlings by cuttings constitutes a fundamental step for achieving the quality standards recommended in commercial fruit growing, and in this crop one of the major challenges to be overcome is the lack of consolidated propagation protocols, in order to ensure quality in the material produced and enable the expansion of cultivation. This study aimed to evaluate the effects of Chlorella sp. extract on the formation and development of seedlings of three commercial pitaya varieties, seeking to contribute to more efficient and environmentally appropriate propagation protocols. The experiment was conducted between July and December 2022 in a nursery with 50% shading at the Federal University of Grande Dourados, Mato Grosso do Sul, using a randomized block design in a 3 × 5 factorial scheme with four replications. Three pitaya varieties were evaluated: Golden (interclonal hybrid with white pulp and yellow skin), Selenicereus costaricensis (purple pitaya), and S. undatus (red pitaya), subjected to five doses of Chlorella sp. extract (0.0, 0.2, 0.4, 0.6, and 0.8 mL plant⁻¹). Evaluations were performed weekly between 35 and 70 days for number, length, and diameter of shoots and, at 75 days, root length and the fresh and dry masses of roots and shoots were measured, allowing the characterization of the initial performance of the varieties in response to the biostimulant doses. The Golden variety showed earlier vegetative development, with greater shoot length (28.78 mm), maximum diameter (39.28 mm) at 53 days, and a higher number of shoots (4.50 shoots plant⁻¹) compared to the Red and Purple varieties. The doses of 0.32 and 0.21 mL plant⁻¹ provided the highest shoot dry mass (5.73 g plant⁻¹) and fresh mass (79.50 g plant⁻¹) in the Golden variety, while the Red and Purple varieties did not show a significant response to the biostimulant application. The extract of the microalga Chlorella sp. proved to be promising for the development of pitaya seedlings, especially for the Golden variety, and further studies exploring different methods and forms of application of the biostimulant are recommended.