Endophytic bacteria Bacillus safensis and Pseudomonas hibiscicola and their ability to increase rice seedling growth

Endophytic bacteria Bacillus safensis RS95 and Pseudomonas hibiscicola RS121 were evaluated for their ability to promote the growth of rice seedlings and produce indole-acetic acid (IAA) and siderophores and to solubilize phosphates. 'Guri' rice seeds were immersed in bacterial endophyte cell suspensions (separated and two-strain mixed), as well as in Escherichia coli DH5α, phosphate-buffered saline (PBS) and water treatments (negative controls). Seeds were sown on agar-water in Petri plates placed vertically at an angle of 65°. The ability of plant growth-promoting endophytic bacteria (PGPEB) to produce IAA and siderophores was determined by Salkowski colorimetric and chrome azurol S (CAS) assays, respectively. Mineral phosphate solubilization activity was calculated by inoculating the endophytes onto medium containing insoluble phosphate. PGPEB showed a positive effect on the growth of rice seedlings, causing a mean growth of shoots and primary-roots of 60 and 67%, respectively. Bacterial strains also showed positive traits for IAA and siderophore production, as well as phosphate-solubilization activity

Somatic embryogenesis in Carica papaya as affected by auxins and explants, and morphoanatomical-related aspects

ABSTRACT The aim of this study was to evaluate somatic embryogenesis in juvenile explants of the THB papaya cultivar. Apical shoots and cotyledonary leaves were inoculated in an induction medium composed of different concentrations of 2,4-D (6, 9, 12, 15 and 18 µM) or 4-CPA (19, 22, 25, 28 and 31 µM). The embryogenic calluses were transferred to a maturation medium for 30 days. Histological analysis were done during the induction and scanning electron microscopy after maturing. For both types of auxin, embryogenesis was achieved at higher frequencies with cotyledonary leaves incubated in induction medium than with apical shoots; except for callogenesis. The early-stage embryos (e.g., globular or heart-shape) predominated. Among the auxins, best results were observed in cotyledonary leaves induced with 4-CPA (25 µM). Histological analyses of the cotyledonary leaf-derived calluses confirmed that the somatic embryos (SEs) formed from parenchyma cells, predominantly differentiated via indirect and multicellular origin and infrequently via synchronized embryogenesis. The secondary embryogenesis was observed during induction and maturation phases in papaya THB cultivar. The combination of ABA (0.5 µM) and AC (15 g L-1) in maturation medium resulted in the highest somatic embryogenesis induction frequency (70 SEs callus-1) and the lowest percentage of early germination (4%).

Indole acetic acid and ACC deaminase from endophytic bacteria improves the growth of Solarium lycopersicum

Background: Endophytic bacteria are ubiquitous in all plant species contributing in host plant's nutrient uptake and helping the host to improve its growth. Moringa peregrina which is a medicinal plant, growing in arid region of Arabia, was assessed for the presence of endophytic bacterial strains. Results: PCR amplification and sequencing of 16S rRNA of bacterial endophytes revealed the 5 endophytic bacteria, in which 2 strains were from Sphingomonas sp.; 2 strains from Bacillus sp. and 1 from Methylobacterium genus. Among the endophytic bacterial strains, a strain of Bacillus subtilis LK14 has shown significant prospects in phosphate solubilization (clearing zone of 56.71 mm after 5 d), ACC deaminase (448.3 ± 2.91 nM α-ketobutyrate mg-1 h-1) and acid phosphatase activity (8.4 ± 1.2 nM mg-1 min-1). The endophytic bacteria were also assessed for their potential to produce indole-3-acetic acid (IAA). Among isolated strains, the initial spectrophotometry analysis showed significantly higher IAA production by Bacillus subtilis LK14. The diurnal production of IAA was quantified using multiple reactions monitoring method in UPLC/MS-MS. The analysis showed that LK14 produced the highest (8.7 uM) IAA on 14th d of growth. Looking at LK14 potentials, it was applied to Solanum lycopersicum, where it significantly increased the shoot and root biomass and chlorophyll (a and b) contents as compared to control plants. Conclusion: The study concludes that using endophytic bacterial strains can be bio-prospective for plant growth promotion, which might be an ideal strategy for improving growth of crops in marginal lands.

Endophytic colonization of rice (Oryza sativa L.) by the diazotrophic bacterium Burkholderia kururiensis and its ability to enhance plant growth

Burkholderia kururiensis is a diazotrophic bacterium originally isolated from a polluted aquifer environment and presents a high level of similarity with the rice endophyte "B. brasilensis" species. This work assessed the ability of B. kururiensis to endophytically colonize rice plantlets by monitoring different tissues of root-inoculated plants for the presence of bacterial growth in different media, electron microscopy and by 16S rDNA analysis. Observations of roots, stems and leaves of inoculated rice plantlets by electron microscopy revealed B. kururiensis colonization predominantly on root hair zones, demonstrating endophytic colonization primarily through the endodermis, followed by spreading into xylem vessels, a possible pathway leading to aerial parts. Although indifferent for the bacterial growth itself, addition of a nitrogen source was a limiting factor for endophytic colonization. As endophytic colonization was directly associated to an enhanced plant development, production of phytohormone auxin/indole-3-acetic acid by B. kururiensis was assayed with transgenic rice plantlets containing an auxin-responsive reporter (DR5-GUS). Our findings suggest the ability of auxin production by plant-associated B. kururiensis which may have a stimulatory effect on plant development, as evidenced by activation of DR5-GUS. We hereby demonstrate, for the first time, the ability of B. kururiensis to endophytically colonize rice, promoting both plant growth and rice grain yield.

Burkholderia kururiensis é uma bactéria diazotrófica, originalmente isolada de um ambiente aquático poluído e apresenta alto nível de similaridade com a espécie endofítica "B. brasilensis" encontrada na planta de arroz. Este artigo demonstrou a habilidade de B. kururiensis colonizar endofiticamente plântulas de arroz, após esta bactéria ter sido inoculada na raiz das plantas. Esta capacidade foi confirmada pelo crescimento bacteriano em diferentes tecidos da planta, por microscopia eletrônica e pela análise do 16S rADN. Observação por microscopia eletrônica das raízes, caule e folhas das plântulas de arroz inoculadas, revelou predominância da colonização de B. kururiensis na zona pilífera da raiz, demonstrando que a colonização endofítica inicia-se na endoderme, espalha-se pelo xilema, sendo esta a possível via para a bactéria alcançar as partes aéreas. A adição de uma fonte de nitrogênio, embora não tenha influenciado no crescimento bacteriano, foi um fator limitante para a colonização endofítica. Como a colonização endofítica mostrou-se diretamente associada ao aumento no desenvolvimento da planta, a produção do fitohormônio auxina/ácido 3-indolacético pela B. kururiensis foi verificada utilizando uma plântula de arroz transgênica, contendo o repórter responsivo para auxina (DR5-GUS). Nossos resultados sugerem que a produção de auxina pela B. kururiensis é responsável pelo estímulo no desenvolvimento da planta verificado pela ativação do DR5-GUS. Neste trabalho demonstramos, pela primeira vez, a habilidade de B. kururiensis colonizar endofiticamente a planta de arroz, promovendo tanto o aumento no crescimento da planta como a produção de sementes de arroz.

Determination of IAA in brassinolide treated coleoptiles of wheat by a modified indirect ELISA with polyclonal antibodies.

An indirect enzyme immunoassay for detection of as little as 10-50 pmole IAA is described for the first time. The assay is based on the development of highly specific polyclonal antibodies against the carboxyl site of IAA. The binding specificity is nearly as high as the radioimmunoassay and the titre of the specific antibody was also remarkably high (1:40,000 of the primary antibody). Such an easy, rapid, specific and highly sensitive assay would be extremely useful in gaining more information on the mode of action of phytohormones, and their effects on physiological processes.

Growth, apical dominance and endogenous hormonal picture of normal, covered and decapitated duranta shoots

The effect of decapitation or covering the shoot apex on growth and endogenous hormonal picture of Duranta repens were studied. It was found that, the decapitated shoots do not increase in length, but carry more lateral branches leading to lowest apical dominance. This was accompanied by the least contents and levels of gibberellins and auxins with the appearance of ABA and highest content and levels of cytokinins. But, the length of intact shoots with exposed apical buds was highly increased with no laterals leading to highest apical dominance accompanied with a hormonal picture opposite to that found in the decapitated shoots. However, the branches with covered apices showed median patterns in growth, apical dominance and endogenous hormonal picture