A study was conducted to determine the effect of inoculation method and plant growth medium on colonization of sorghum by an endophytic Beauveria bassiana. Colonization of leaves, stems, and roots by B. bassiana was assessed 20-days after application of the fungus. Although B. bassiana established as an endophyte in sorghum leaves, stems, and roots regardless of inoculation method (leaf, seed, or soil inoculation), plant growth medium (sterile soil, non-sterile soil, or vermiculite) apparently influenced colonization rates. Seed inoculation with conidia caused no stem or leaf colonization by the fungus in non-sterile soil but did result in substantial endophytic colonization in vermiculite and sterile soil. Leaf inoculation did not result in root colonization, regardless of plant growth medium. Endophytic colonization was greater in leaves and stems than roots. Endophytic colonization by B. bassiana had no adverse effects on the growth of sorghum plants. Leaf inoculation with a conidial suspension proved to be the best method to introduce B. bassiana into sorghum leaves for plants growing in either sterile or non-sterile soil. Further research should focus on the virulence of endophytic B. bassiana against sorghum stem borers.

Summary: Herbaceous plants harbour species‐rich communities of asymptomatic endophytic fungi. Although some of these endophytes are entomopathogenic, many are not, and remarkably little is known about how the presence of these fungi in plant tissues affects phytophagous insects. Here we show through a meta‐analysis that both entomopathogenic and nonentomopathogenic endophytes have a negative effect on insect herbivores. Growth and performance of polyphagous and sucking insects are reduced by nonentomopathogenic endophytes, but monophages are unaffected, likely because the latter are better adapted to secondary metabolites produced or induced by the fungi. Furthermore, studies using excised leaves report weaker effects than those with intact plants, likely caused by chemical changes being masked by leaf excision. Most surprisingly, endophyte infection of seeds produces the greatest effect on insect herbivores in subsequent mature plants, even though the usual mode of fungal transmission is infection of leaves by airborne spores. We conclude that these ubiquitous hidden fungi may be important bodyguards of plants. However, in order to fully understand their roles in plant protection, we must be aware that minor differences in experimental design can lead to contradictory results.

Recently the role of micro-organisms as mediators of plant-herbivore interactions has been increasingly acknowledged in ecological research. We investigated the interaction between an unspecialized root fungal endophyte (Acremonium strictum) and the polyphagous moth Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), in greenhouse and laboratory bioassays. Specifically we examined in tomato (Lycopersicon esculentum Mill.) the systemic effects of the endophytic fungus on the host selection behaviour of female moths for oviposition and the volatile profiles of host plants to understand the mechanisms acting in this multi-trophic model system. Both laboratory and field strains of H. armigera moths oviposited more on leaves of A. strictum inoculated plants as compared to endophyte-free plants, both in free flight cages and in tethered moth laboratory experiments; the moth’s preferences were significant between 10 and 18 days after inoculation. The analysis of volatile profiles showed strong quantitative differences between treatments. Endophyte inoculated plants emitted diverse terpenes and sesquiterpenes at significantly lower amounts as compared to endophyte free-plants, except for α-terpinene, which did not differ between the treatments, and trans-β-caryophyllene, which was emitted in significantly higher amounts on inoculated plants. β-Thujene and α-phellandrene accounted for 73.3 and 12.0% of total amounts of volatiles emitted from endophyte-free and inoculated plants, respectively. Our findings demonstrate that A. strictum is able to systemically influence the host selection of H. armigera moths for oviposition; conceivably mediated by the induced changes in volatile emissions (and probably additional biochemical parameters of the host plants, which have not been analysed so far). We argue for a more detailed assessment of micro-organisms invisibly colonizing plants, when studying plant-herbivore or multitrophic interactions.

The endophytic plant-fungi symbiotic relationship can be explored to improve cultivation of targeted medicinal plant species. The objective of this study was to assess the effects of the cultivation of chive (Allium schoenoprasum) in plant growth medium inoculated with the entomopathogenic fungus, Beauveria bassiana (Hypocreales). Twelve replicates of chive seedlings were exposed to B. bassiana inoculum formulated at concentrations of 0, 1 × 105, 1 × 104 and 1 × 103 conidia mL-1 in a completely randomized design. We assessed plant growth parameters, such as leaf number and plant height weekly and root length, leaf and root fresh and dry weights and secondary metabolites three weeks post-fungal inoculation. The fungus was re-isolated from some of the leaves and roots of the treated plants suggesting that the fungus successfully colonized the plant tissue. Generally, the results indicated that the fungal inoculation had minimal effect on most of the growth parameters assessed in relation to the control. Remarkably, plants exposed to the fungus recorded greater (p < 0.05) total alkaloid, ranging from 2.98 - 3.76 mg atropine equivalent (AE)/g dry weight (DW) compared to the control plants (1.96 mg AE/g DW) for the leaves. This study demonstrated that endophytic fungi could be used to improve the yield of active chemical constituents in cultivated medicinal plants.

A greenhouse experiment was conducted to evaluate the effect of soil-dwelling larvae of the western corn rootworm, Diabrotica virgifera virgifera LeC

Summary: There is increasing evidence that extrafloral (EF) nectaries, described in approximately 1000 plant species from more than 90 families, have a defensive function. Endophytic fungi are an important group of microorganisms asymptomatically colonizing host plants, and promoting their defences against natural enemies. We aimed at investigating the role of these microorganisms in inducing EF nectary defences in plants against herbivory. We conducted a full factorial experiment to study the effects of a soil‐borne endophytic fungus, Acremonium strictum, alone or in combination with the aphid, Aphis fabae, on the production of EF nectar and nectaries in broad beans. By manipulating the presence/absence of the fungus in the roots of the host plants and by inflicting herbivore damage at a specific time and location, we tested the hypothesis that endophyte inoculation induces EF‐mediated indirect defences. The quantity of EF nectar production and the number of EF nectaries produced were assessed by repeated samplings at fixed intervals. Endophytic inoculation of bean plants induced a significant short‐term increase in total EF nectar production and a significant prompt increase in number of EF nectaries per expanded leaf. On the other hand, aphid infestation resulted in a prolonged increase in total EF nectar production and a delayed induction of EF nectaries. Conversely, when plants were simultaneously inoculated with the endophyte and infested with aphids, both EF traits were significantly reduced. The effect of endophyte inoculation was further examined by recording the life history traits of Aphis fabae. Aphid performance was generally lower on inoculated plants; however, relative fecundity was the only fitness parameter significantly reduced on endophyte inoculated plants. The organism model in the present study serves as a model for investigating how endophytic colonization alters the response of EF nectary traits to herbivory. From a cost/benefit perspective, variable responses in EF‐mediated indirect defences as influenced by endophytes could be explained as trade‐offs in defence. In addition, other possibilities that may have contributed to the EF response patterns reported in this study are discussed.