Isolation, Culture, and Behavior of Frankia Strain HFPCgI4 from Root Nodules of Casuarina glauca

Abstract

Casuarina glauca (Casuarinaceae) is an important introduced tree species in Egypt, valued for windbreaks, land stabilization, and soil improvement associated with actinomycete-induced root nodules that fix atmospheric nitrogen. A strain of Frankia designated HFPCgI4 was isolated from root nodules collected in Egypt and its characteristics assessed both in pure culture and in symbiosis. Strain CgI4 grows well in synthetic nutrient medium with added NH4+ or, in the absence of combined N in the medium, forms vesicles and fixes dinitrogen adequate for growth. Hyphae, vesicles, sporangia, and spores characteristic of the genus Frankia were observed. This strain shows spontaneous spore release when grown in media lacking N. When tested for infectivity on actinorhizal host plants grown in unaerated water culture, CgI4 nodulates several species of Casuarina that fix atmospheric dinitrogen. Other genera in the Casuarinaceae, namely, Allocasuarina and Gymnostoma, were not nodulated under these conditions. Species of the genus Myrica and Comptonia peregrina (Myricaceae) were effectively nodulated by CgI4. The isolate may have use as an inoculant for forest plantations using species of Casuarina sensu stricta.

<i>In-planta</i> Sporulation Capacity Enhances Infectivity and Rhizospheric Competitiveness of <i>Frankia</i> Strains

“…Spores released by Sp+ nodule tissues may completely invade the vicinity of the roots. Germination may occur in the soil in response to root secondary compounds, producing infective hyphae that may, in turn, induce new infections ( 16 , 22 , 42 , 49 ). Alternatively, spores may also directly attach to the roots, as described for many species of sporulating biotrophic fungal pathogens ( 21 , 48 ).…”

Influence of salt stress on inoculated Casuarina glauca seedlings

“…For propagation, Frankia strains were grown in B medium (Murry et al 1984) for 3 weeks, then the cells were harvested and washed in distilled water with centrifugation, and homogenization was applied. The homogenized hyphae (inoculum) were applied dropwise along the roots of each seedling using 0.01 ml Paced cell volume (PCV) of culture per seedling following the method of Mansour et al (1990). Three jars containing uninoculated seedlings served as negative controls.…”

Permanent Draft Genome sequence for Frankia sp. strain CcI49, a Nitrogen-Fixing Bacterium Isolated from Casuarina cunninghamiana that Infects Elaeagnaceae

“…strain CcI49 was isolated from root nodules of Casuarina cunninghamiana grown on the edge of a cultivated field on side of the highway in Ismailia-Port Said, Egypt. The fresh nodules were washed, dissected into individual lobes, and surface-sterilized as described previously 13 . Each lobe was checked for sterility in sterile nutrient-rich medium.…”