Persistence and Viability of Lecanicillium lecanii in Chinese Agricultural Soil

Abstract

The entomopathogenic fungus L. lecanii has been developed as biopesticides and used widely for biological control of several insects in agricultural practice. Due to the lack of isolation/count methods for L. lecanii in soil, the persistence of this fungus in soil appears to have attracted no attention. A selective medium and count method for L. lecanii in soil based on cetyl trimethyl ammonium bromide (CTAB) was developed, and then the persistence and viability of this fungus in soil were investigated under field conditions between 2012 and 2014. The results showed that the rate of recovery for L. lecanii in soil on the selective CTAB medium was satisfactory. The minimum CFUs for L. lecanii on the selective medium (0.5 g/L CTAB) was about 102 conidia/g soil. The L. lecanii density in soil declined quickly in the first month after inoculation with fungal conidia, kept stable for 6 to 10 months, and then decreased gradually until undetectable. L. lecanii could persist for at least 14 months in the agricultural soil of northern China. The colony growth, conidia yield and germination rate on plates, as well as the median lethal concentration or times (LC50 or LT50) to aphids, mycelium growth in aphids and sporulation on aphids of L. lecanii did not change significantly during the persistence in soil. In general, the count method developed here was a very useful tool for monitoring the dynamics of natural or introduced L. lecanii populations in soil, and the data on the persistence of L. lecanii in soil reported here were helpful for biological control and environmental risk assessment.

Establishment of polyethylene‐glycol‐mediated protoplast transformation for Lecanicillium lecanii and development of virulence‐enhanced strains against Aphis gossypii

“…Inoculated insects were collected at 12 h intervals during the course of the infection, with residual conidia on the surface of insects washed away using an ultrasonic cleaner, dried in preweighed petri dishes at 70 °C until the weight was constant and then used for DNA extraction. The mycelium growth in insects was quantified by quantitative real‐time PCR (qPCR) using the primer pair Lec ‐F/R as described previously . Firstly, a tenfold dilution series of purified fungal DNA (100–0.001 ng µL −1 ) as templates were used to perform qPCR with the SYBR‐Green PCR Master Mix kit (Omega Bio‐Tek, Norcross, GA) in an ABI 7500 PCR (Applied Biosystems, Foster City, CA).…”

“…The mycelium growth in insects was quantified by quantitative real-time PCR (qPCR) using the primer pair Lec-F/R as described previously. 31 Firstly, a tenfold dilution series of purified fungal DNA (100-0.001 ng μL −1 ) as templates were used to perform qPCR with the SYBR-Green PCR Master Mix kit (Omega Bio-Tek, Norcross, GA) in an ABI 7500 PCR (Applied Biosystems, Foster City, CA). Secondly, plotting logarithmic values of DNA concentration versus C t values (threshold cycle number) generated a standard curve.…”

Genetic improvement of the nematicidal fungus Lecanicillium attenuatum against Heterodera glycines by expression of the Beauveria bassiana Cdep1 protease gene

“…Colony growth, conidial yield and germination rates on PDA plates were tested as described for L. lecanii (Xie et al, 2015). Fungal conidia were incubated in protease-inducing (PI) liquid medium and protease activity was measured as described previously (Yang et al, 2007).…”

Effects ofLecanicillium lecaniistrain JMC-01 on the physiology, biochemistry, and mortality ofBemisia tabaciQ-biotype nymphs

“…Lecanicillium lecanii (= Verticillium lecanii (Zimmerman)Viegas) belongs to Deuteromycotina, Hyphomycetes, Moniliales, Moniliaceae, that is widely use entomopathogenic fungi in bio-control up to now. And the entomopathogenic fungal species described and commercialized, L. lecanii (Zare & Gams, 2001) deserves further consideration as a broad range commercial biopesticide, due to its wide range of hosts and wide geographical distribution (Xie et al, 2015). Indeed, this species can infect the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) (Ravindran et al, 2018), aphids (Hemiptera: Aphididae) (Askary, Benhamou & Brodeur, 1999), the citrus mealybug Planococcus citri Risso (Hemiptera: Pseudococcidae) (Ghaffari et al, 2017), and the soybean cyst nematode Heterodera glycines Ichinohe (Tylenchida: Heteroceridae) (Shinya et al, 2008), and has also been documented to infect Bemisia tabaci (Zhu & Kim, 2011).…”