Congolese Rhizospheric Soils as a Rich Source of New Plant Growth-Promoting Endophytic Piriformospora Isolates

Abstract

In the last decade, there has been an increasing focus on the implementation of plant growth-promoting (PGP) organisms as a sustainable option to compensate for poor soil fertility conditions in developing countries. Trap systems were used in an effort to isolate PGP fungi from rhizospheric soil samples collected in the region around Kisangani in the Democratic Republic of Congo. With sudangrass as a host, a highly conducive environment was created for sebacinalean chlamydospore formation inside the plant roots resulting in a collection of 51 axenically cultured isolates of the elusive genus <i>Piriformospora</i> (recently transferred to the genus <i>Serendipita</i>). Based on morphological data, ISSR fingerprinting profiles and marker gene sequences, we propose that these isolates together with <i>Piriformospora williamsii</i> constitute a species complex designated <i>Piriformospora</i> (= <i>Serendipita</i>) '<i>williamsii.</i>' A selection of isolates strongly promoted plant growth of <i>in vitro</i> inoculated <i>Arabidopsis</i> seedlings, which was evidenced by an increase in shoot fresh weight and a strong stimulation of lateral root formation. This isolate collection provides unprecedented opportunities for fundamental as well as translational research on the Serendipitaceae, a family of fungal endophytes in full expansion.