Molecular insight into the endophytic growth of Beauveria bassiana within Phaseolus vulgaris in the presence or absence of Tetranychus urticae

Biocontrol Screening of Endophytes: Applications and Limitations

The considerable loss of crop productivity each year due to plant disease or pathogen invasion during pre- or post-harvest storage conditions is one of the most severe challenges to achieving the goals of food security for the rising global population. Although chemical pesticides severally affect the food quality and health of consumers, a large population relies on them for plant disease management. But currently, endophytes have been considered one of the most suitable biocontrol agents due to better colonization and acclimatization potential. However, a very limited number of endophytes have been used commercially as biocontrol agents. Isolation of endophytes and their screening to represent potential characteristics as biocontrol agents are considered challenging by different procedures. Through a web search using the keywords "endophytes as biocontrol agents" or "biocontrol mechanism of endophytes," we have succinctly summarised the isolation strategies and different in vitro and in vivo biocontrol screening methods of endophytic biocontrol agents in the present review. In this paper, biocontrol mechanisms of endophytes and their potential application in plant disease management have also been discussed. Furthermore, the registration and regulatory mechanism of the endophytic biocontrol agents are also covered.

Production of Purpureocillium lilacinum and Pochonia chlamydosporia by Submerged Liquid Fermentation and Bioactivity against Tetranychus urticae and Heterodera glycines through Seed Inoculation

Pochoniachlamydosporia and Purpureocilliumlilacinum are fungal bioagents used for the sustainable management of plant parasitic nematodes. However, their production through submerged liquid fermentation and their use in seed treatment have been underexplored. Therefore, our goal was to assess the effect of different liquid media on the growth of 40 isolates of P. lilacinum and two of P. chlamydosporia. The most promising isolates tested were assessed for plant growth promotion and the control of the two-spotted spider mite (Tetranychus urticae) and the soybean cyst nematode (Heterodera glycines). Most isolates produced > 108 blastospores mL−1 and some isolates produced more than 104 microsclerotia mL−1. Microsclerotia of selected isolates were used to inoculate common bean (Phaseolus vulgaris L.) seeds in greenhouse trials. All fungal isolates reduced the T. urticae fecundity in inoculated plants through seed treatment, while P. chlamydosporia ESALQ5406 and P. lilacinum ESALQ2593 decreased cyst nematode population. Purpureocillium lilacinum was more frequently detected in soil, whereas P. chlamydosporia colonized all plant parts. Pochonia chlamydosporia ESALQ5406 improved the root development of bean plants. These findings demonstrate the possibility of producing submerged propagules of P. chlamydosporia and P. lilacinum by liquid culture, and greenhouse trials support the applicability of fungal microsclerotia in seed treatment to control P. vulgaris pests.

Can colonization by an endophytic fungus transform a plant into a challenging host for insect herbivores?

Endophytic growth of arthropod pathogenic fungi can parasitize insect herbivores without causing damage to the crop. However, studies addressing this tritrophic interaction are absent. Here, the endophytic arthropod pathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordyciptaceae), the polyphagous two-spotted spider mite Tetranychus urticae Koch (Trombidiformes: Tetranychidae), and its preferred plant host Phaseolus vulgaris L. (Fabales: Fabaceae) were selected to study the multi-kingdom interactions among plants, arthropods, and entomopathogenic fungi. Real-Time PCR analysis of nine defense-related genes revealed that a broad range of plant defense mechanisms is activated in response to the endophytic growth of B. bassiana. Moreover, we studied the molecular mechanism adapted by the two-spotted spider mite that underlies resistance. The analysis of 41 detoxification genes revealed that relatively moderate, high, and few numbers of genes were changed in the adults, nymphs, and eggs stages of T. urticae, respectively, after inoculation on colonized tissues of P. vulgaris. The endophytic growth of B. bassiana can have a negative effect on the growth and performance of the pest, in a developmental stage-dependent manner, by priming plant defense pathways. In parallel, the herbivore induces a broad range of detoxification genes that could potentially be involved in adaptation to endophytically colonized plant tissues.