Gernot Vobis

Additions to the Lichen Flora of Tierra del Fuego

Abstract Four species of lichens are reported as new to South America, namely the cosmopolitan or bipolar Dermatocarpon polyphyllum and Xylographa abietina, and the austral Hypocenomyce australis and H. foveata. The following four taxa are reported for the first time for Argentina: Baeomyces rufus, Cystocoleus ebeneus, Lecanora intricate, and Placynthiella icmalea, and the range of Trapeliopsis granulose is extended to Tierra del Fuego.

Potential biocontrol actinobacteria: Rhizospheric isolates from the Argentine Pampas lowlands legumes.

Control of fungal plant diseases by using naturally occurring non‐pathogenic microorganisms represents a promising approach to biocontrol agents. This study reports the isolation, characterization, and fungal antagonistic activity of actinobacteria from forage soils in the Flooding Pampa, Argentina. A total of 32 saprophytic strains of actinobacteria were obtained by different isolation methods from rhizospheric soil of Lotus tenuis growing in the Salado River Basin. Based on physiological traits, eight isolates were selected for their biocontrol‐related activities such as production of lytic extracellular enzymes, siderophores, hydrogen cyanide (HCN), and antagonistic activity against Cercospora sojina, Macrophomia phaseolina, Phomopsis sp., Fusarium oxysporum, and Fusarium verticilloides. These actinobacteria strains were characterized morphologically, physiologically, and identified by using molecular techniques. The characterization of biocontrol‐related activities in vitro showed positive results for exoprotease, phospholipase, fungal growth inhibition, and siderophore production. However, none of the strains was positive for the production of hydrogen cyanide (HCN). Streptomyces sp. MM140 presented the highest index for biocontrol, and appear to be promising pathogenic fungi biocontrol agents. These results show the potential capacity of actinobacteria isolated from forage soils in the Argentine Pampas lowlands as promising biocontrol agents, and their future agronomic applications.

Synergy of Actinomycete Co-inoculation

Historically the symbioses between leguminous plants and rhizobia have attracted the attention of researchers due to the incidence of legumes for sustaining nutritional requirements to humans and animals. There have been large efforts to increase the ability to symbiotic N2 fixing and productivity of legumes. New research is focusing on increasing the legume–rhizobia symbiosis with increased biological nitrogen fixation (BNF), growth, and productivity. The inoculation of legumes with rhizosphere bacteria has often been found to increase symbiotic properties, plant biomass, and yields under greenhouse or field conditions. The potential to enhance plant growth, nodulation, nitrogen fixation, productivity of legumes by plant growth-promoting rhizobacteria (PGPR), and Rhizobium co-inoculation does exist, although most of studies have been conducted with Bacillus spp., Pseudomonas spp., or other genera and few with actinomycetes. The latter, a group of actinobacteria widely distributed in terrestrial ecosystems contribute to soil nutrient cycling and live in association with plants and are considered as one of the most important communities in the rhizosphere. They have a great ability to synthesize a series of bioactive metabolites and potential within the agroecosystem, where they play important roles in disease suppression and plant growth promotion in cultivated plants. In this sense, the purpose of this chapter is to show the synergistic effect of actinomycete co-inoculation on N2-fixing symbioses and their potential use in agriculture.