Purpureocillium lilacinum and Metarhizium marquandii as plant growth-promoting fungi

Abstract

Background Especially on commodities crops like soybean, maize, cotton, coffee and others, high yields are reached mainly by the intensive use of pesticides and fertilizers. The biological management of crops is a relatively recent concept, and its application has increased expectations about a more sustainable agriculture. The use of fungi as plant bioinoculants has proven to be a useful alternative in this process, and research is deepening on genera and species with some already known potential. In this context, the present study focused on the analysis of the plant growth promotion potential of Purpureocillium lilacinum, Purpureocillium lavendulum and Metarhizium marquandii aiming its use as bioinoculants in maize, bean and soybean. Methods Purpureocillium spp. and M. marquandii strains were isolated from soil samples. They were screened for their ability to solubilize phosphorus (P) and produce indoleacetic acid (IAA) and the most promising strains were tested at greenhouse in maize, bean and soybean plants. Growth promotion parameters including plant height, dry mass and contents of P and nitrogen (N) in the plants and in the rhizospheric soil were assessed. Results Thirty strains were recovered and characterized as Purpureocillium lilacinum (25), Purpureocillium lavendulum (4) and Metarhizium marquandii (1). From the trial for P solubilization and IAA production, seven strains were selected and inoculated in maize, bean and soybean plants. These strains were able to modify in a different way the evaluated parameters involving plant growth in each crop, and some strains distinctly increased the availability of P and N, for the last, an uncommon occurrence involving these fungi. Moreover, the expected changes identified at the in vitro analysis were not necessarily found in planta. In addition, this study is the first to evaluate the effect of the isolated inoculation of these fungi on the growth promotion of maize, bean and soybean plants.

Metarhizium: jack of all trades, master of many

“…In addition to suppression of herbivores via nematophagous or entomophagous activities, Metarhizium species have multiple such direct growth-promoting effects on plants. These are still being elucidated but include solubilizing rock phosphorus in soil making it more accessible to plants [ 138 ], and transfer of nitrogen by hyphae connecting insect cadavers and plant roots [ 139 ]. As quid pro quo, M. robertsii exchanges this insect-derived nitrogen [ 139 ] for ‘photosynthesate’ i.e.…”

“…As befits an ancient association, there is evidence that sophisticated and subtle signalling underlie plant– Metarhizium interactions. Beauveria bassiana and several Metarhizium species including M. marquandii produce the phytohormone IAA (indole acetic acid), the best-known auxin, through Trp-dependent pathways [ 132 , 138 ] ( figure 5 ). IAA is involved in tropism responses, cell division, vascular tissue differentiation and the initiation of root formation [ 143 ], and its synthesis by Metarhizium species modifies the root architecture, increasing the root area for colonization by Metarhizium and boosting uptake of nutrients by the plant [ 132 ] ( figure 5 ).…”

Paecilomyces and Its Importance in the Biological Control of Agricultural Pests and Diseases

“…The plant– Paecilomyces interaction improves plant health through different mechanisms and provides protection from phytopathogens [ 38 ]. This interaction showed a production of phytohormones, such as gibberellins and indole-acetic acid, that promoted growth and mitigated the effects of abiotic stress, such as salinity [ 39 , 40 ]. When used indirectly in combination with pathogenic agents such as nematodes or fungi, Paecilomyces has positive effects on crop growth by acting as a biological control agent [ 41 , 42 , 43 , 44 ].…”

Endophytic Fungi: Biological Control and Induced Resistance to Phytopathogens and Abiotic Stresses

“…Some biological agents colonize the plant, which often present biostimulating effects. Baron et al [ 91 ] showed that P. lilacinum and Metarhizium marquandii promote growth in maize, bean and soybean plants when used as bioinoculants. They observed indoleacetic acid (IAA) production and phosphorus solubilization, showing the biostimulating effect of these endophytes in addition to their effects against plant pathogens.…”