Primavera otoño 2020 (Año LXIII Núms. 122-123)

horizontes@pucpr.edu Año LXIV Núm. 124-125 horizontes PRIMAVERA / OTOÑO 2021 PUCPR 77 Main Analysis Plant material Citrus fruits propagate asexually by copying the genetics of an extracted part of the plant, known as an explant. In vitro propagation guarantees an identical copy of the characteristics to be multiplied (Vibhute et al., 2016). Studies have shown that nodal segments are the best explant to use because their tissue is constantly differentiating. Besides the nodal segments, meristematic tissues such as stems, epicotyl, roots, and leaves are suitable explants in citrus micropropagation, achieving organ development (Bulbarela-Marini et al., 2019). When cloned, the organism’s genetic makeup passes to its clone, including the maturation rate. Tzatzani et al. (2018) explored in vitro organogenesis using epicotyls and internodal segments. In woody plants such as citrus, the organism’s age copied during cloning; if the tissue was young, it delayed growth, and the mature tissue showed little proliferation of shoots. The main disadvantage of mature tissue is that it takes years to reach the desired age. It can speed up in vitro the slow growth that the nodal segments present in the field (Pandey & Tamta, 2016). Researchers grew 1.5 cm cotyledonary nodes from seeds sown in a Murashige and Skoog growth medium supplemented with the phytohormone N6- benzylaminopurine for 45 days. The explant showed up to a maximum of 4 shoots per sample, good organogenesis, vigorous growth, and free of pathogens. The same in vitro growth took 0.5 cm pieces of leaves and planted them in a Murashige, and Skoog culture medium combined with 2,4-D dichlorophenoxy acetic acid to create calluses to extract biological compounds. The selection of the explant with the sterilization process was the first step in micropropagation that influenced the finished product. Sterilization In vitro propagation has the persistence of pathogenic microorganisms in the explant selected from the plant. In sterilization processes, the concentration of the chemical agent and the type of explant must be considered because prolonged exposure to high concentrations damages tissue (Lazo-Javalera et al., 2016). To sterilize, the agent concentration and the contact time were critical. Oo et al. (2018) compared sterilization protocols with apical tips and nodal segments from micro propagated strawberry, Fragaria ananassa. They treated the nodal segments with 10 mL / L of Homine™ (a fungicide) for two hours, 500 mg / L of ciprofloxacin (an antibiotic) for one hour, 20% Clorox™ (bleach) with Tween™ (nonionic detergent) for five minutes, 70% ethanol for five minutes, and 0.1% mercury chloride for four minutes. This potent sterilization protocol was suitable for nodal segments but created apical tip tissue damage. A less-damaging protocol used pathogen-free tissue to start axillary buds in vitro regeneration of grapevine ( Vitis vinifera L.). Sterilization eliminated pathogenic organisms by applying 20% Clorox™ with 50 drops / L of surfactant for 60 minutes (Lazo-Javalera et al., 2016). This treatment did not affect tissue integrity and attained 90% pathogen-free samples. Although this protocol employed only one sanitizing agent, it involved a long contact time of 60 minutes to assure its effectiveness. Sterilization of Vitis vinifera is comparable to that of Citrus × latifolia because both are woody plants with similar pathogens. Bulbarela-Marini et al. (2019), in micropropagation, worked with nodal segments of Citrus × latifolia , sterilized with 30% Clorox™ for 15 minutes, 70% ethanol for 1 minute, and washed three times with