A window into fungal endophytism in Salicornia europaea: deciphering fungal characteristics as plant growth promoting agents

Aim Plant-endophytic associations exist only when equilibrium is maintained between both partners. This study analyses the properties of endophytic fungi inhabiting a halophyte growing in high soil salinity and tests whether these fungi are beneficial or detrimental when non-host plants are inoculated. Method Fungi were isolated from Salicornia europaea collected from two sites differing in salinization history (anthropogenic and naturally saline) and analyzed for plant growth promoting abilities and non-host plant interactions. Results Most isolated fungi belonged to Ascomycota (96%) including dematiaceous fungi and commonly known plant pathogens and saprobes. The strains were metabolically active for siderophores, polyamines and indole-3-acetic acid (mainly Aureobasidium sp.) with very low activity for phosphatases. Many showed proteolytic, lipolytic, chitinolytic, cellulolytic and amylolytic activities but low pectolytic activity. Different activities between similar fungal species found in both sites were particularly seen for Epiccocum sp., Arthrinium sp. and Trichoderma sp. Inoculating the non-host Lolium perenne with selected fungi increased plant growth, mainly in the symbiont (Epichloë)-free variety. Arthrinium gamsii CR1-9 and Stereum gausapatum ISK3-11 were most effective for plant growth promotion. Conclusions This research suggests that host lifestyle and soil characteristics have a strong effect on endophytic fungi, and environmental stress could disturb the plant-fungi relations. In favourable conditions, these fungi may be effective in facilitating crop production in non-cultivable saline lands

Plant growth promoting characteristics of soil yeast ('Candida tropicalis' HY) and its effectiveness for promoting rice growth

Compared with bacteria and mycorrhizal fungi, the potential to use yeasts as plant growth promoting agents has been under-exploited. We investigated the ability of the soil yeast 'Candida tropicalis' HY (CtHY) to stimulate rice seedling growth and some of the possible mechanisms by which plant interaction may occur. Laboratory culture experiments found that CtHY produces small quantities of indole acetic acid (IAA), but grows rapidly on aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, indicative of high ACC deaminase activity. The strain also tested positive for polyamine and phytase production, and mobilized phosphate from insoluble tri-calcium phosphate. CtHY rapidly colonized the roots of rice seedlings and maintained high numbers for at least 3 weeks, increasing the dry weight of inoculated roots by 16-35% compared to non-inoculated control seedlings. These results validate the inclusion of CtHY in the commercial biofertiliser product BioGro, which has previously been demonstrated to increase the nutrition, growth and yield of paddy rice

Field monitoring of plant-growth-promoting rhizobacteria by colony immunoblotting

Inoculant plant-growth-promoting bacteria are emerging as an important component of sustainable agriculture. There is a need to develop inexpensive methods for enumerating these organisms after their application in the field, to better understand their survival and impacts on yields. Immunoblotting is one potential method to measure viable cells, but the high cost of the conventionally used nylon membranes makes this method prohibitive. In this study, less expensive alternative materials such as filter papers, glossy photo papers, and transparencies for the purpose of colony immunoblotting were evaluated and the best substance was chosen for further studies. Whatman filter paper No. 541 combined with a 0.01 mol.L⁻¹ H₂2SO₄ rinsing step gave similar results to nylon membranes but 10⁷ CFU.g⁻¹) of the plant-growth-promoting bacteria 'Pseudomonas fluorescens', 'Azospirillum brasilense', or 'Rhizobium leguminosarum'. The modified protocol allowed the identification and recovery of over 50% of the inoculated cells of all three strains, amidst a background of the native soil microflora. Subsequently, the survival of 'P. fluorescens' was successfully monitored for several months after application to field-grown rice at Jerilderie, New South Wales, Australia, thus validating the procedure