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Black pod rot is the most important disease affecting Theobroma cacao in Cuba. Plant growth promoting bacteria (PGPB) are considered an alternative for controlling plant disease in the context of the integrated management. The present work was aimed to evaluate Pseudomonas chlororaphis strain CP07, isolated from T. cacao rhizosphere, as potential PGPB against P. palmivora in cacao plants cultivated under controlled conditions. Three genotypes of Cuban traditional cacao of the group Trinitario and the genotype UF 677 were used. The effect of CP07 was evaluated by using detached leaf tests and in planta assays with plants obtained in vitro from both seeds and micrografting. Inoculation of P. palmivora in control plants showed that genotypes EICB-371, EICB-384 and UF 677 were highly susceptible to the disease (71.4 to 99% disease severity) while EICB-385 was significantly less susceptible (39 to 54.5%). In EICB-371 and EICB-385 genotypes, disease symptoms were significantly reduced in presence of CP07 compared to the control plants in all assays. In contrast, for EICB-384 and UF 677 genotypes, there was not reduction of disease severity in plants pre-treated with CP07. Results show the protective effect of treating cacao plants with CP07 against P. palmivora. Plant genotype significantly influenced the protective ability of bacteria affecting the CP07-mediated disease control. Results suggest that depending on cacao genotype, CP07 has a potential for inducing plant defense against P. palmivora which can be used in the control of black pod rot.

The inability to discover novel class of antibacterial agents, especially against Gram-negative bacteria (GNB), compel us to consider a broader non-conventional approach to treat infections caused by multidrug-resistant (MDR) bacteria. One such approach is the use of adjuvants capable of revitalizing the activity of current existing antibiotics from resistant pathogens. Recently, our group reported a series of tobramycin (TOB)-based hybrid adjuvants that were able to potentiate multiple classes of legacy antibiotics against various MDR GNB. Herein, we report the modification of TOB-based hybrid adjuvants by replacing TOB domain by the pseudo-disaccharide nebramine (NEB) through selective cleavage of the α- d -glucopyranosyl linkage of TOB. Potent synergism was found for combinations of NEB-based hybrid adjuvants with multiple classes of legacy antibiotics including fluoroquinolones (moxifloxacin and ciprofloxacin), tetracyclines (minocycline), or rifamycin (rifampicin) against both wild-type and MDR P. aeruginosa clinical isolates. We also demonstrated that a combination of the optimized NEB-CIP hybrid 1b and rifampicin protects Galleria mellonella larvae from the lethal effects of extensively drug-resistant (XDR) P. aeruginosa. Mechanistic evaluation of NEB-based hybrid adjuvants revealed that the hybrids affect the outer- and inner membranes of wild-type P. aeruginosa PAO1. This study describes an approach to optimize aminoglycoside-based hybrids to yield lead adjuvant candidates that are able to resuscitate the activity of partner antibiotics against MDR GNB.

The aim of this work was to select and characterize native Cuban fluorescent Pseudomonas from the rhizosphere of Oryza sativa with in vitro and in vivo antagonistic activity against Pyricularia oryzae. A total of 200 isolates were recovered with the typical growth and cultural characteristics of fluorescent Pseudomonas. The results showed that 12.5% of total isolates were capable of inhibiting mycelial growth, with different levels of inhibition between strains. Six of them (AI03, AI05, AI08, AJ01, AJ13 and AJ29) were able to reduce disease severity and incidence in vivo whereas only four (AI05, AJ13, AJ01 and AI08) showed efficient control of P. oryzae in greenhouse conditions. Pseudomonas fluorescens AI05 and Pseudomonas putida AJ13 were able to inhibit in vitro the mycelial growth of P. oryzae and to reduce symptom severity of Pyricularia infection. The production of lytic enzymes, siderophores, hydrogen cyanide (HCN), as well as the detection of genes encoding antibiotics and bacterial motility were also assessed for both strains. They were able to fix nitrogen, produce indolic compounds and to solubilize Pi. These results demonstrate the potential use of P. fluorescens AI05 and P. putida AJ13 as a biocontrol agent for the protection of rice plants from P. oryzae infection. Key words: Biocontrol, rice blast, Pyricularia, Pseudomonas, plant growth-promoting bacteria.

This study aimed to evaluate in vitro grafting of Theobroma cacao where seedlings of the UF 677 genotype were used as the rootstock and apices or axillary buds of a Trinitarian genotype were used as scion. Three methods of grafting using scions from seedlings were evaluated. Apical grafts using apex and side grafts using apex displayed better graft success (95 and 80%, respectively). However, side grafts using axillary buds reached a greater height on average and a higher number of leaves per plant (1.76 cm and 3.72, respectively). Histological studies revealed new vascular elements at the graft union area. Side grafts with axillary buds provided the highest survival rate (82%) after the acclimatization step. A shoot of at least 1 cm with two leaves is required for plant survival after transfer to ex vitro conditions. Side grafting was carried out with axillary buds from adult trees and nursery plants. Only the grafts with buds from nursery grafted plants were successful, with a rate of 26%. Overa...

Introduction Theobroma cacao L. is economically speaking the most important species of the genus Theobroma . Cacao is cultured in tropical regions and its yield is affected by several diseases, such as black pod. Black pod rot in cacao . Cacao black pod, particularly, is an economically serious problem in all areas of the world where cacao is grown, causing significant pod losses of up to 30% and killing up to 10% of the trees annually. The disease is caused by different species of the stramenopile genus Phytophthora and, once it has infected a cacao field, its control is fairly difficult. Black pod rot control strategies . Several approaches are used to manage black pod: chemical control, phytosanitary and cultural methods, genetic resistance, and biological control. Losses in yield due to black pod could be reduced through integrated management practices, although the results may vary for each cacao-growing region. Main challenges and new approaches Black pod control could be achieved if an integrated management strategy is established, with the combination of biological and chemical methods, genetic control, and adequate cultural methods in an integrated program.

Plants growth promoting bacteria (PGPB) are capable of increasing directly or indirectly crop yield. Burkholderia and Pseudomonas have been found in large populations, which inhabit in the rhizosphere of several agriculture crops. The aim of this study was to determine the antagonistic activity in vitro and in vivo of Cuban native plant growth promoting rhizobacteria against Fusarium verticillioides M1, and to assess their ability to produce IAA and to promote plant growth. The bacterial strains were tested to assess their fungal growth inhibition and plant growth stimulation. The plant growth assays were done in a modified microcosm experiment and in greenhouse conditions. The results demonstrated that these rhizobacteria produce IAA and exhibit antagonistic effect on F. verticillioides M1 inoculated in the substrate. Burkholderia sp. MBf21, MBp1, MBf15 and Pseudomonas fluorescens MPp4 stood out for their plant growth stimulation in maize and for the biological control exerted on F. verticillioides M1. The strains Burkholderia sp. MBf21 and MBf15 showed the best results in disease suppression, which was achieved up to 80%. These results have practical relevance, since potentially effective bacterial strains were selected and could be used in agriculture, for the enhancement of plant growth and disease control in maize crop.

Aim: To isolate and characterize rhizobacteria from Theobroma cacao with antagonistic activity against Phytophthora palmivora, the causal agent of the black pod rot, which is one of the most important diseases of T. cacao. Methods and Results: Among 127 rhizobacteria isolated from cacao rhizosphere, three isolates (CP07, CP24 and CP30) identified as Pseudomonas chlororaphis, showed in vitro antagonistic activity against P. palmivora. Direct antagonism tested in cacao detached leaves revealed that the isolated rhizobacteria were able to reduce symptom severity upon infection with P. palmivora Mab1, with Ps. chlororaphis CP07 standing out as a potential biocontrol agent. Besides, reduced symptom severity on leaves was also observed in planta where cacao root system was pretreated with the isolated rhizobacteria followed by leaf infection with P. palmivora Mab1. The production of lytic enzymes, siderophores, biosurfactants and HCN, as well as the detection of genes encoding antibiotics, the formation of biofilm, and bacterial motility were also assessed for all three rhizobacterial strains. By using a mutant impaired in viscosin production, derived from CP07, it was found that this particular biosurfactant turned out to be crucial for both motility and biofilm formation, but not for the in vitro antagonism against Phytophthora, although it may contribute to the bioprotection of T. cacao. Conclusions: In the rhizosphere of T. cacao, there are rhizobacteria, such as Ps. chlororaphis, able to protect plants against P. palmivora. Significance and Impact of the Study: This study provides a theoretical basis for the potential use of Ps. chlororaphis CP07 as a biocontrol agent for the protection of cacao plants from P. palmivora infection. © 2015 The Society for Applied Microbiology.

El arroz es fuente de alimento para una gran parte de la población mundial, con alto promedio de consumo anual. En este cultivo las enfermedades de origen microbiano constituyen uno de los factores que inciden en la obtención de bajos rendimientos y calidad de los granos. La piriculariosis o añublo del arroz, causada por Pyricularia grisea, es la enfermedad más importante en este cultivo en América Latina, ya que puede provocar hasta el 100% de reducción de los rendimientos. Como parte de la estrategia de agricultura sostenible, se trata de controlar estos patógenos y lograr altos rendimientos del cultivo mediante una combinación adecuada de fertilizantes químicos y productos biológicos. En este sentido, la aplicación de inoculantes bacterianos constituidos por bacterias promotoras del crecimiento vegetal (Plant Growth- Promoting Bacteria, PGPB, por sus siglas en inglés) ha constituido una alternativa ecológica que favorece la conservación del medioambiente y el ecosistema. Este trabajo tiene como objetivo abordar el estado actual y las perspectivas de uso de bacterias rizosféricas en el control de Pyricularia grisea en el cultivo del arroz, tratando algunos temas relevantes, como son las principales enfermedades que afectan al cultivo, los géneros de PGPB más utilizados para el control de las mismas y sus principales mecanismos de acción. Rice is an important food supply for a large part of the world population and its consumption rates are very high. Microbial diseases are one of the main causes that provoke low yields and low-quality spotted grains. Although fungi, bacteria and viruses are mostly the responsible for these losses, fungal diseases strike more frequently. Among fungi, Pyricularia grisea, the blast fungus is responsible for up to 100% of reduction in yields, being the blast the most important rice disease in Latin America. To control this pathogen, a strategy of sustainable agriculture might be developed, combining accurately chemical and biological products. PGPB based bioproducts have been considered as an eco-friendly alternative, which favours environment preservation. This work was aimed to approach the current status and outlook of the use of rhizobacteria in the biocontrol of Pyricularia grisea on rice. Main diseases attacking rice, most beneficial PGPB and its mechanisms of action will be discussed too in this review.