Introduction:

Some entomopathogenic fungi act as endophytes and promote plant growth. Such benefits can be explained by improvements in physiological processes. In this research, the effect of commercial strains of entomopathogenic endophytic fungi and isolates from agricultural soils of San Luis Potosi on growth, photosynthesis, gas exchange and production in poblano chili plants was evaluated, considering the effect of the inoculation method used.

Methodology:

Poblano chili plants (Capsicum annuum L.) was used as a model which was sown under controlled conditions and in a greenhouse. Seven HEE strains were evaluated: three native isolates from agricultural soils of San Luis Potosi that by their characteristics belong to the genus Metarhizium (RV01 strain), Paecilomyces (RV05 strain) and Penicillium (SL14 strain); two strains isolated from insects, Beauveria bassiana [(Bals.-Criv.) Vuill. 1992] (BB42 strain) and Metarhizium anisopliae [(Metschn.) Sorokin 1883) (MA25 strain) and two commercial strains of B. bassiana (BB09 strain) and M. anisopliae (MA25 strain). A conidial solution was prepared, and two methods were tested: 1) seed inoculation; and 2) substrate spraying and a second application when the first true leaf emerged. Controls were included in each treatment (water and the surfactant were inoculated). Photosynthetic parameters (maximum and effective efficiency of PSII, photochemical and non-photochemical dissipation, electron transfer rate), gas exchange parameters (net assimilation rate, stomatal conductance, and transpiration) and colonization percentage of steam, leaf and root were evaluated during the experiment. At the end of the experiment total dried biomass, dry weight of the aerial part of the plant and the root, and root length was measured.

Results:

At 33 days after inoculation it was observed how inoculation with RV01, MA25, BB09 and SL14 increased CO2 assimilation and stomatal conductance, with respect to controls, when inoculated by seed or by spraying. Inoculation directly over the seed significantly improved CO2 assimilation, photochemical quenching, and effective efficiency of PSII comparing to plants inoculated by foliar spraying. The isolate RV05 stood out due to the results observed in the greenhouse, with a higher total biomass production. The plants inoculated by seed showed an increase in the production of total biomass, and in the dry weight of the aerial part and roots with respect to the plants inoculated by aspersion. Greater growth in plants was associated with endophytic colonization.

Conclusion:

HEE isolated from agricultural soils of San Luis Potosi can compete with commercial strains in promoting growth in poblano chili plants in greenhouse. Direct seed inoculation of endophytic entomopathogenic fungi generated better results, although with variations depending on the strain.

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