Survival of Pochonia chlamydosporia on the soil surface after different exposure intervals at ambient conditions / Supervivencia de Pochonia chlamydosporia en la superficie del suelo después de diferentes intervalos de exposición a condiciones ambientales

Background. Exposure of the nematophagous fungus Pochonia chlamydosporia to solar radiation and elevated temperatures before being incorporated into the soil can reduce its survival and efficiency as biocontrol agent. Aims. A field experiment was carried out to assess the effect of the exposure period on the viability of P. chlamydosporia applied on the soil surface. Methods. A commercial bionematicide based on P. chlamydosporia was sprayed on soil, and soil samples were collected before and at 0, 30, 60, 90, 120, and 150 min after fungal application. Relative humidity (RH), the irradiance (IR), air temperature (AT), and soil temperature (ST) were recorded. The number of P. chlamydosporia colony forming units (CFUs) was evaluated after 20 days of incubation. Results. P. chlamydosporia survival decreased over the time of exposure on the soil surface. Overall, the number of CFUs decreased by more than 90% at 150min after application. Exposure to RH ≥61%, ST and AT between 25-35°C and 19-29°C, and IR between 1172 and 2126μmol of photons m−2s−1 induced a negative exponential effect on the survival of the fungus over the time. Conclusions. Exposure to climatic conditions on the soil surface reduces P. chlamydosporia viability (AU)

Antecedentes. La exposición del hongo nematófago Pochonia chlamydosporia a la radiación solar y la temperatura elevada antes de ser incorporado al suelo puede reducir su supervivencia y eficiencia como agente de biocontrol. Objetivos. Se realizó un experimento de campo para evaluar el efecto del período de exposición a condiciones ambientales sobre la viabilidad de P. chlamydosporia en la superficie del suelo. Métodos. Se pulverizó sobre el suelo un bionematicida comercial hecho a base de P. chlamydosporia y se recogieron muestras de suelo antes y después de 0, 30, 60, 90, 120 y 150min tras la aplicación del hongo. Se registraron la humedad relativa (HR), la irradiación (IR), la temperatura del aire (TA) y la temperatura del suelo (TS). Se evaluó el número de unidades formadoras de colonias (UFC) de P. chlamydosporia después de 20 días de incubación. Resultados. La supervivencia de P. chlamydosporia disminuyó durante el tiempo de exposición en la superficie del suelo. En general, el número de UFC disminuyó en más de un 90% a los 150min después de la aplicación. La exposición a HR≥61%, TS y TA entre 25-35°C y 19-29°C, e IR entre 1.172 y 2.126μmol de fotones m−2 s−1 indujo un efecto exponencial negativo en la supervivencia del hongo. Conclusiones. La exposición a las condiciones climáticas en la superficie del suelo reduce la viabilidad de P. chlamydosporia (AU)

Survival of Pochonia chlamydosporia on the soil surface after different exposure intervals at ambient conditions.

BACKGROUND: Exposure of the nematophagous fungus Pochonia chlamydosporia to solar radiation and elevated temperatures before being incorporated into the soil can reduce its survival and efficiency as biocontrol agent. AIMS: A field experiment was carried out to assess the effect of the exposure period on the viability of P. chlamydosporia applied on the soil surface. METHODS: A commercial bionematicide based on P. chlamydosporia was sprayed on soil, and soil samples were collected before and at 0, 30, 60, 90, 120, and 150min after fungal application. Relative humidity (RH), the irradiance (IR), air temperature (AT), and soil temperature (ST) were recorded. The number of P. chlamydosporia colony forming units (CFUs) was evaluated after 20 days of incubation. RESULTS: P. chlamydosporia survival decreased over the time of exposure on the soil surface. Overall, the number of CFUs decreased by more than 90% at 150min after application. Exposure to RH ≥61%, ST and AT between 25-35°C and 19-29°C, and IR between 1172 and 2126µmol of photons m-2s-1 induced a negative exponential effect on the survival of the fungus over the time. CONCLUSIONS: Exposure to climatic conditions on the soil surface reduces P. chlamydosporia viability.

Pochonia chlamydosporia e Bacillus subtilis no controle de Meloidogyne incognita e M. javanica em mudas de tomateiro / Pochonia chlamydosporia and Bacillus subtilis on the control of Meloidogyne incognita and M. javanica in tomato seedlings

O objetivo deste estudo foi avaliar o efeito da aplicação de Pochonia chlamydosporia no solo e a microbiolização de sementes de tomateiro com Bacillus subtilis no controle de Meloidogyne incognita e M. javanica em condições de casa de vegetação. Os tratamentos foram constituídos pela incorporação no solo de 20g de milho triturado colonizado ou não pelo fungo, com ou sem microbiolização das sementes com a suspensão bacteriana (DO540 = 0,5) por 24 h. O solo dos vasos foi infestado com 5.000 ovos de M. javanica ou M. incognita. Nenhum tratamento alterou a massa da parte aérea e das raízes dos tomateiros em ambos os experimentos, tampouco reduziu o número de galhas dos nematoides aos 45 dias após o transplantio das mudas e infestação do solo. A microbiolização das sementes de tomateiro com B. subtilis reduziu em 62,6% o número de ovos de M. incognita, quando comparado com as sementes não tratadas, independentemente da aplicação do fungo. A combinação entre microbiolização de sementes com B. subtilis e a aplicação de P. chlamydosporia reduziu em mais de 80% o número de ovos de M. javanica em comparação com a adoção de apenas um dos tratamentos isoladamente.

The aim of this study was to evaluate the effect of the application of Pochonia chlamydosporia into the soil and tomato seeds soaked in Bacillus subtilis cell suspension on the control of Meloidogyne incognita and M. javanica under greenhouse conditions. The treatments were incorporation into the soil of milled corn (20 g) colonized or not by the fungus, with or without seeds treatment with bacterial suspension (OD540 = 0,5) for 24 h. The soil of each pot was infested with 5,000 eggs of M. javanica or M. incognita. Neither the biomass of tomato plants nor the number of galls were influenced by the treatments 45 days after seedlings transplanting and soil infestation in both the experiments. Seed microbiolization with B. subtilis reduced the number of eggs of M. incognita by 62.6%, in comparison to non-treated seeds, regardless of the application of the fungus. The combination of seed microbiolization with B. subtilis and application of P. chlamydosporia reduced more than 80% the number of eggs of M. javanica, when compared to each separate treatment.