Controle de bactérias visando à propagação in vitro de pimenteira-do-reino

Abstract

Black pepper (Piper nigrum L.) is a perennial plant belonging to the botanical family Piperaceae of Indian origin. Brazilian black pepper stands out for its quality in terms of aroma, flavor, and pungency. To produce black pepper, the plant is propagated sexually (seeds) or asexually (cuttings). In vitro propagation through tissue culture is a technique that has been used to produce large-scale, healthy, and pathogen-free plants. However, factors such as the presence of endogenous microorganisms in black pepper tissues affect in vitro plant regeneration. Therefore, this work aimed to evaluate the efficiency in the control of endophytic bacteria in vitro in two black pepper genotypes. The experiment was carried out at the Laboratory of Genetic Resources and Plant Biotechnology at Embrapa Amazônia Oriental, located in Belém/Pará. The explants used were from two genotypes: reciprocal intraspecific hybrids called H5 (Guajarina X Bento) and H20 (Bento X Guajarina) with bacteria in plants kept in laboratory cultivation. The culture medium used for in vitro propagation was MS basic medium supplemented with 0.5 mg L-1 BAP (6-benzylaminopurine) and 0.2 mg L-1 of IAA (indolylacetic acid) with the biocide PPM® (Plant Preservative Mixture) at different concentrations (0, 1, 5, 10, 20 mL L-1). After 30 days of installation of the experiment, it was possible to observe that there was an effect of the doses of PPM® in the culture medium, in the control of bacteria in vitro. Thus, genotypes responded similarly between dosages. For height there was an optimal dosage of 6.9 mL L-1 of PPM®, but when the dosages were decreased or increased, a reduction in plant development was observed. The optimal dosage for the number of leaves (in both hybrids) was 6.35 mL L-1 to have an average of 1.33 leaves, but when supplementing the culture medium with higher concentrations of PPM®, there was a decline in the number of leaves. Regarding contamination, as the concentration of PPM® increased, the contamination was reduced. However, when supplementing the culture medium with higher doses, the explant did not show development, demonstrating phytotoxicity characteristics. It is concluded that there is control of bacteria such as the use of PPM®, at a concentration of 20 mL L-1 for the hybrids H5 and H20, however, the dose does not allow the development of explants, causing a toxic effect on the hybrids. The maintenance of PPM® dosages is necessary for the next subcultures to observe if there is a decrease in bacterial manifestation, as well as to test asepsis methodologies with immersion of black pepper explants in PPM® solution and it is suggested to do the identification of possible bacteria.