Abstract Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (foc) is one of the main diseases affecting banana crops. Biological control emerges as an alternative technology to prevent the spread of the disease. The objective of this work was to evaluate the effects of endophytic bacteria isolated from banana Prata Anã challenged with the foc in pairing and volatile tests under in vitro conditions. Forty endophytic isolates of the genera Bacillus, Klebsiella, Paenibacillus, Stenotrophomonas, Lysinibacillus and Sporolactobacillus isolated from banana roots were challenged with foc. The principal component analysis showed that the spore germination variable in the presence of bacterial cells explained better the variance (29.88%). Spore germination in the presence of bacterial cells, number of spores/cm2 in paired and volatile tests, and colony area in volatile tests explained about 86.10% of the total variance observed. The isolate EB37 (Bacillus sp., JN215502.1) reduced 96% of the germination of Fusarium oxysporum f. sp. cubense spores. The UPMGA clustering method based on Euclidean distance divides the 40 endophytic bacteria isolates into eight groups. The autochthonous bacteria isolated from Musa sp. of the genera Bacillus, Lysinibacillus, Stenotrophomonas, Sporolactobacillus and Paenibacillus showed promising results in foc control under in vitro conditions.

Abstract: The banana tree is associated with different species of endophytic bacteria that can stimulate plant growth. However, further studies are needed to better understand the relationships between this group of bacteria and the host plant. The objective of this study was to investigate the localization of the EB-40 (Bacillus sp.) through anatomical and ultrastructural analyses in micropropagated banana plantlets. The results demonstrated the effective colonization of the EB-40 isolate in the intercellular and intracellular spaces, as well as in the rhizosphere region. The wall of endophytic bacteria contains calcium and nitrogen. The EB-40 isolate was also observed to associate with the plasma membrane and cell wall. These results further our understanding of the mechanisms involved in the colonization of plant cells by endophytic bacteria in micropropagated banana plantlets.

ABSTRACT Forty isolates of endophytic bacteria isolated from banana tree roots were assessed as to their capacity to solubilize phosphate in a solid culture medium supplemented with different inorganic and one organic source of phosphorus. The amount of phosphorus (P) in each liquid medium was quantified, and an indirect assessment of acid phosphatase activity was performed. All assays had a fully randomized design, with three repetitions. Approximately 67.5% of the 40 isolates assessed in solid medium solubilized phosphorus from tricalcium phosphate and 7.5% of the isolates solubilized phosphorus from soy lecithin; no isolates exhibited P solubilization capacity in medium supplemented with iron phosphate. Acid phosphatase activity was detected in 65% of the isolates; Aneurinibacillus sp. and Lysinibacillus sp. isolates presented with the best solubilization indexes. All of the assessed isolates exhibited a capacity to reduce the potential of hydrogen in liquid medium supplemented with tricalcium phosphate. Isolate EB. 78 (Bacillus sp.) exhibited P solubilization capacity in solid media when Ca3(PO4)2 and soy lecithin were used as P sources; this isolate significantly reduced the pH of the liquid medium and exhibited acid phosphatase activity. The results of the present study highlight isolates that exhibit variations in their capacity to solubilize P. These isolates should be used in future tests to assess their field performance.

RESUMO: Agentes de controle biológico associados com matéria orgânica é uma estratégia que pode potencializar o controle dos nematoides-das-galhas. Objetivou-se neste trabalho avaliar o efeito de materiais orgânicos e rizobactérias sobre Meloidogyne javanica em tomateiro. Utilizou-se o delineamento em blocos casualizados, em esquema fatorial 4x2+1, sendo quatro materiais orgânicos (turfa, biofertilizante, esterco bovino e composto orgânico de casca de pequi), dois isolados de rizobactérias (Bacillus pumilus -1 e B. pumilus - 76) e adubação mineral (tratamento adicional), com oito repetições. Mudas de tomateiro foram transplantadas para vasos contendo solo arenoso, ao qual incorporaram-se os diferentes materiais orgânicos. As suspensões das rizobactérias (OD 540=0,5) foram aplicadas ao solo via rega. O solo de cada vaso foi infestado com aproximadamente 3000 ovos e eventuais juvenis de segundo estádio de M. javanica. Todos os materiais orgânicos associados às rizobactérias reduziram o número de galhas e massas de ovos de M. javanica em comparação à adubação mineral. Já o número de juvenis (J2) foi menor nas combinações pequi + B. pumilus-1 e B. pumilus-76 e turfa + B. pumilus-1. O número de ovos e o fator de reprodução foram influenciados pela interação entre as rizobactérias e os compostos. Para o composto de pequi, B. pumilus-1 promoveu menor número de ovos por grama de raiz, enquanto para turfa, B. pumilus-76 foi a mais eficiente. Para o fator de reprodução, apenas o esterco foi influenciado pela bactéria, sendo que B. pumilus-1 foi a que proporcionou menor capacidade reprodutiva do nematoide.

ABSTRACT: Biological control agents associated with organic matter is a strategy that can enhance the control of root-knot nematode. The objective of this study was to evaluate the effect of organic materials and rhizobacteria on Meloidogyne javanica on tomato. We used the randomized block design, in a 4x2+1 factorial scheme, four organic materials (peat, bio-fertilizer, manure and organic compound of pequi hulls), two isolates of rhizobacteria (Bacillus pumilus-1 and B. pumilus-76) and mineral fertilization alone (additional treatment), with eight replications. Tomato seedlings were transplanted to pots containing sandy soil, in which the different organic materials were incorporated. Suspensions of rhizobacteria (OD 540=0,5) were applied to soil by means of irrigation. The soil in each pot was infested with approximately 3,000 eggs and eventual second stage juveniles (J2) of M. javanica. All organic materials associated with rhizobacteria reduced the number of galls and masses of M. javanica eggs compared to mineral fertilizer. The number of juveniles (J2) was lower in combinations pequi + B. pumilus-1 and B. pumilus-76 and peat + B. pumilus-1. The number of eggs and the reproduction factor were influenced by the interaction between rhizobacteria and organic materials. For the compound of pequi, B. pumilus-1 produced a lower number of eggs per gram of root, while for peat, B. pumilus-76 was the most efficient. For the reproduction factor, only the manure was influenced by the bacterium, and B. pumilus-1 was the one that provided lower reproductive capacity of the nematode.

The genetic diversity of endophytic bacteria in banana 'Prata Anã' roots was characterized. Two hundred and one endophytic bacteria were isolated, 151 of which were classified as Gram-positive and 50 as Gram-negative. No hypersensitivity response was observed in any of the isolates. The rep-PCR technique generated different molecular profiles for each primer set (REP, ERIC and BOX). Fifty readable loci were obtained and all of the fragments were polymorphic. Amplified ribosomal DNA restriction analysis (ARDRA) of the isolates based on cleavage with four restriction enzymes yielded 45 polymorphic bands and no monomorphic bands. PCR amplified the nifH gene in 24 isolates. 16S rDNA sequencing of the 201 bacterial isolates yielded 102 high-quality sequences. Sequence analyses revealed that the isolates were distributed among ten bacterial genera (Agrobacterium, Aneurinibacillus, Bacillus, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Paenibacillus, Rhizobium and Sporolactobacillus) and included 15 species. The greatest number of isolates belonged to the genus Bacillus. The bacteria identified in this study may be involved in promoting growth, phosphate solubilization, biological control and nitrogen fixation in bananas.