Abstract
The Atlantic Forest is a biome that has suffered anthropic actions, such as the extraction of hardwood, which can lead to the extinction of endemic species of great economic and ecological value, such as Dalbergia nigra. In this perspective, large-scale multiplication studies are necessary to contribute to the conservation of this species. The objective of this work was to establish a protocol for the in vitro production of axenic seedlings of D. nigra. Four experiments were performed: I. Immersion times in NaOCl. II. Disinfecting agents in seed germination of D. nigra. III. NaOCl toxicity in seeds of the model species Lactuca sativa L. IV. Culture media and glutamine in the germination and initial growth of D. nigra. All experiments were arranged in a completely randomized design. For a better disinfestation and less harmful effects to the seedlings, it is recommended that the seeds be treated with 70% alcohol (1 min) and NaOCl (14 min). NaOCl has a high phytotoxic, cytotoxic, and genotoxic effect, and its mechanism of action in the L. sativa cell cycle is clastogenic and aneugenic, suggesting the formation of abnormal seedlings in D. nigra. The WPM medium and its supplementation with glutamine (0.75 mg.L-1) are recommended.
Highlights
Mature seeds of Dalbergia nigra harvested from matrices located in Viçosa, Minas Gerais (20°45’35.1”S, 42°52’06.1”W) and obtained with the Society of Forest Investigations (SIF) of the Federal University of Viçosa (UFV) were used in the experiment
The different immersion times in NaOCl showed no significant difference for the variables of contamination, germination, non-germinated seeds, germination speed index (GSI), mean germination time: (MGT), abnormal seedlings, total seedling length, leaf number, collar diameter, and total seedling dry mass (Figure 1)
In D. nigra, above 14 min of exposure of the seeds to NaOCl, there was a reduction in seedling normality (Figure 1)
Summary
Due to the intense exploitation of its timber resources, along with anthropogenic actions on the forest, attacks by pests (Troezon championi Lima) on seeds, and predators (Sylvilagus brasiliensis Linnaeus) on seedlings, its population has been disappearing and is on the Red List of Threatened Species (Brasil, 2014; Leite et al, 2014). In vitro germination is an alternative for the propagation of species with difficulty for seminiferous multiplication under natural conditions, allowing largescale production in a shorter period of time and space, besides obtaining seedlings with high phytosanitary quality (Franceschi et al, 2019). One of the major problems faced in in vitro propagation is the explant disinfestation and its establishment free of contaminants, which may be either of exogenous (fungus) origin, limiting the tissue surface, or endogenous (bacteria), localized within the organism (Karmakar et al, 2019; Mendy et al, 2019), and making multiplication unfeasible
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