BACKGROUND
Trichoderma spp. are soil fungi that interact with plant roots and associated biota such as other microorganisms and soil fauna. However, information about their interactions with root‐feeding insects is limited. Here, interactions between Trichoderma harzianum and the root‐feeding insect Phyllophaga vetula, a common insect pest in maize agroecosystems, were examined.
RESULTS
Applications of T. harzianum and P. vetula to the root system increased and decreased maize growth, respectively. Induced tolerance against herbivore attack was provided by T. harzianum maintaining a robust and functional root system as evidenced by the increased uptake of Cu, Ca, Mg, Na and K. Herbivore tolerance also coincided with changes in the emission of root volatile terpenes known to induce indirect defense responses and attract natural enemies of the herbivore. More importantly, T. harzianum induced de novo emission of several sesquiterpenes such as β‐caryophyllene and δ‐cadinene. In addition, single and combined applications of T. harzianum and P. vetula altered the sucrose content of the roots. Finally, T. harzianum produced 6‐pentyl‐2H‐pyran‐2‐one (6‐PP) a volatile compound that may act as an antifeedant‐signaling compound mitigating root herbivory by P. vetula.
CONCLUSION
Our results provide novel information about belowground multitrophic plant–microbe–arthropod interactions between T. harzianum and P. vetula in the maize rhizosphere resulting in alterations in maize phenotypic plant responses, inducing root herbivore tolerance.
We analyzed the combined effects of population density and presence or absence of shelters on growth and physiological performance of the crayfish Cambarellus montezumae. Three different densities-64, 144, and 208 crayfish per m 2 -with and without shelters were used. Growth; survival; metabolic rate; tissue glucose; and total lipid, triglyceride, nitrogen, and energy content were measured. Animals stocked at 64 and 144 per m 2 with shelter reached the highest body weight; those in groups without shelter had elevated levels of glucose (p < .05). Animals stocked at 144 per m 2 retained the most nitrogen and energy (p < .05). Overall, the combination of medium density with shelters produced the best performance.
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