Abstract Here we sequenced and characterized the complete plastome of Bactris riparia, a species closely related to B. gasipaes and widely distributed in Western Amazonia. We performed a comparative genomic analysis with B. riparia and the other four Bactridinae species retrieved from GenBank. The plastome of B. riparia was 156,715 bp with a quadripartite structure. Gene content included 86 protein-coding genes (CDS), 38 tRNAs, and 8 rRNAs. Bactris riparia has 69 more base pairs than B. gasipaes, with identical numbers in IR, and more in LSC and SSC. The comparative analysis indicated that structure, collinearity, and IR/SSC borders of plastomes within subtribe Bactridinae are, in general, conserved. We predicted 69 SSRs in B. riparia plastome. Among them, ~80% consisted of A/T homopolymers. Among the 52 variable CDS, rbcL showed the highest non-synonymous rate, while the rps15 gene had the highest synonymous rate. Three genes (ccsA, cemA, and rpoC1) presented evidence of positive selection and 22 genes showed evidence of purifying selection. The phylogenetic tree based on plastome sequences set Bactris as more closely related to Astrocaryum than to Acrocomia. These new plastome data of B. riparia will contribute to studies about the diversity, evolutionary history, and conservation of palms.

RESUMO Na micropropagação de plantas, a etapa de estabelecimento é dificultada pela presença de micro-organismos em tecidos oriundos de matrizes do campo, especialmente para bambu. Objetivou-se estabelecer um protocolo eficiente de assepsia de explantes de Bambusa oldhamii oriundos de plantas em campo e efetuar a identificação molecular de um possível isolado bacteriano endofítico. Os explantes foram expostos subsequentemente a álcool 70 %, hipoclorito de sódio 1 % (NaOCl), cloreto de mercúrio 0,1 % (HgCl2), tiofanato-metílico (Cercobin®) e digliconato de clorexidina (Riohex® 2 %), em diferentes combinações, e introduzidos em meio Murashige and Skoog (sólido ou líquido), acrescido ou não de 4 mL L-1 de Plant Preservative Mixture (PPMTM), em sete tratamentos. A assepsia e imersão dos explantes no meio de cultura líquido contendo 4 mL L-1 de PPMTM inibiram visualmente o crescimento de bactérias e fungos, permitiram o desenvolvimento de brotações com comprimento médio de 2,2 cm e posteriores subcultivos, sendo o melhor tratamento usado para o estabelecimento in vitro de B. oldhamii. A identificação molecular da bactéria por meio do sequenciamento do 16S rDNA permitiu identificar o isolado bacteriano como Ralstonia sp., com 100 % de similaridade, e as análises filogenéticas o agruparam com Ralstonia pickettii. Além disso, a bactéria se mostrou sensível a 4 mL L-1 de PPMTM pelo teste de concentração mínima inibitória.

ABSTRACT In plant micropropagation, the establishment stage is difficult, due to the presence of microorganisms in tissues from field-grown matrices, especially for bamboo. This study aimed to establish an efficient asepsis protocol for Bambusa oldhamii explants from field plants, as well as to carry out the molecular identification of a possible endophytic bacterial isolate. The explants were exposed to 70 % alcohol, 1 % sodium hypochlorite (NaOCl), 0.1 % mercuric chloride (HgCl2), thiophanate-methyl (Cercobin®) and chlorhexidine digluconate (2 % Riohex®) in different combinations, and introduced into Murashige and Skoog culture medium (solid or liquid), supplemented or not with 4 mL L-1 of Plant Preservative Mixture (PPMTM), totaling seven treatments. The asepsis and immersion of the explants in the liquid culture medium containing 4 mL L-1 of PPMTM visually inhibited the bacterial and fungal growth, allowed the development of shoots with a mean length of 2.2 cm and posterior subcultures, being the best treatment used for the in vitro establishment of B. oldhamii. The molecular identification of an endophytic bacterium performed by 16S rDNA sequencing allowed to identify the bacterial isolate as Ralstonia sp., with 100 % of similarity, and the phylogenetic analysis grouped it with Ralstonia pickettii. In addition, the bacterial isolate showed to be sensitive to 4 mL L-1 of PPMTM by the minimum inhibitory concentration test.

RESUMO Bambusa oldhamii Munro é uma espécie de bambu lenhoso de crescimento rápido e com forte apelo comercial. No Brasil, o uso dessa espécie é limitado, devido, principalmente, à baixa disponibilidade de mudas para plantios comerciais. A micropropagação é uma técnica de produção de mudas em larga escala, porém, protocolos de estabelecimento de culturas assépticas são dificultados pela presença de contaminação endofítica. Objetivou-se desenvolver um protocolo de estabelecimento in vitro de B. oldhamii, bem como efetuar a identificação molecular de fungos associados aos explantes utilizados. Segmentos nodais de plantas adultas cultivadas a campo foram utilizados como explantes. Esse material foi submetido a dois experimentos, avaliando-se o efeito de 6-benzylaminopurine (BAP) na multiplicação e de Plant Preservative Mixture (PPMTM) na desinfestação. No primeiro, foram utilizadas concentrações de BAP de 10 µM, 15 µM ou 20 µM, combinadas com 1 mL L-1, 2 mL L-1 ou 3 mL L-1 de PPMTM, e, no segundo, 0 µM, 2,5 µM, 5 µM ou 7,5 µM de BAP, com 4 mL L-1 de PPMTM, ambos adicionados a meio de cultura MS. Após 21 dias de cultivo, o uso de 4 mL L-1 de PPMTM inibiu o crescimento bacteriano e reduziu a contaminação fúngica. A presença de BAP no meio de cultura acima de 10 µM inibiu a formação e o crescimento de brotos novos, enquanto as concentrações inferiores a 7,5 µM não tiveram efeito. A identificação molecular dos fungos endofíticos isolados durante a cultura in vitro indicou a presença de inúmeras espécies fúngicas, ampliando o conhecimento sobre a diversidade de fungos associados ao bambu.

ABSTRACT Bambusa oldhamii Munro is a fast-growing species of woody bamboo with strong commercial appeal. In Brazil, the use of this species is limited, mainly due to the low availability of seedlings for commercial plantations. Micropropagation is a technique used for the large scale production of seedlings, but protocols for the establishment of aseptic cultures are hampered by the presence of endophytic contamination. This study aimed to develop an in vitro establishment protocol for B. oldhamii, as well as to make the molecular identification of fungi associated with the explants used. Nodal segments of adult plants grown in the field were used as explants. This material was submitted to two experiments carried out to evaluate the effect of 6-benzylaminopurine (BAP) on multiplication and of Plant Preservative Mixture (PPMTM) as a disinfectant. In the first one, 10 µM, 15 µM or 20 µM of BAP were combined with 1 mL L-1, 2 mL L-1 or 3 mL L-1 of PPMTM; while the second one used 0 µM, 2.5 µM, 5 µM or 7.5 µM of BAP with 4 mL L-1 of PPMTM, both added to MS culture medium. After 21 days of culture, the use of 4 mL L-1 of PPMTM inhibited the bacterial growth and reduced fungal contamination. The addition of BAP to the culture medium above 10 µM inhibited the formation and growth of new shoots, while additions of less than 7,5 µM had no effect. The molecular identification of the endophytic fungi isolated during the in vitro culture indicated the presence of numerous fungal species, increasing the current knowledge about the diversity of fungi associated with bamboo.