Influence of Additives on the Yield and Pathogenicity of Conidia Produced by Solid State Cultivation of an Isaria javanica Isolate

Abstract

Recently, the Q biotype of tobacco whitefly has been recognized as the most hazardous strain of Bemisia tabaci worldwide, because of its increased resistance to some insecticide groups. As an alternative control agent, we selected an Isaria javanica isolate as a candidate for the development of a mycopesticide against the Q biotype of sweet potato whitefly. To select optimal mass production media for solid-state fermentation, we compared the production yield and virulence of conidia between 2 substrates (barley and brown rice), and we also compared the effects of various additives on conidia production and virulence. Barley was a better substrate for conidia production, producing 3.43 × 1010 conidia/g, compared with 3.05 × 1010 conidia/g for brown rice. The addition of 2% CaCO3 + 2% CaSO4 to barley significantly increased conidia production. Addition of yeast extract, casein, or gluten also improved conidia production on barley. Gluten addition (3% and 1.32%) to brown rice improved conidia production by 14 and 6 times, respectively, relative to brown rice without additives. Conidia cultivated on barley produced a mortality rate of 62% in the sweet potato whitefly after 4-day treatment, compared with 53% for conidia cultivated on brown rice. The amendment of solid substrate cultivation with additives changed the virulence of the conidia produced; the median lethal time (LT50) was shorter for conidia produced on barley and brown rice with added yeast extract (1.32% and 3%, respectively), KNO3 (0.6% and 1%), or gluten (1.32% and 3%) compared with conidia produced on substrates without additives.

Beauveria bassiana for the simultaneous control of Aedes albopictus and Culex pipiens mosquito adults shows high conidia persistence and productivity

“…To develop appropriate fungal insecticides, virulence to the target insect, conidia persistence and conidia productivity are important factors (Lopez-Perez et al 2015; Muñiz-Paredes et al 2017). Recently, several studies have been conducted on various media that can increase the conidial productivity of fungi (Lopez-Perez et al 2015; Kim et al 2014; Safavi et al 2007; Shah et al 2005). However, when the basic conidia productivity of the fungus is low, the replacement of the medium is a limitation.…”

Dibutyl succinate, produced by an insect‐pathogenic fungus, Isaria javanica pf185, is a metabolite that controls of aphids and a fungal disease, anthracnose

“…We found that the antifungal activity of I. javanica pf185 was influenced by different carbon and nitrogen sources, and growth temperature (Lee YS et al .). Our previous study showed that pathogenicity on a whitefly of another I. javanica isolate, pf05, was affected by growth medium and temperature . The spectrum of insects targeted by dibutyl succinate is being expanded by current investigations with whitefly and mites.…”

Effects of Temperature and Culture Media Composition on Sporulation, Mycelial Growth, and Antifungal Activity of Isaria javanica pf185

“…Palm kernel oil was a cost-effective substrate promoting spore production for I. javanica and B. bassiana, and when coupled with high humidity, the formulations caused high mortality of whitefly (do Nascimento Silva et al, 2018). Additions of CaCO 3 , CaSO 4 , and powders of silkworm and moth larvae to cultures of I. javanica pf05 enhanced spore production to promote virulence against whitefly (Kim et al, 2014;Xie et al, 2016).…”

“…Conidial formation is influenced by the types of carbon (C) and nitrogen (N) sources and the C:N ratio (Gao and Liu, 2010;Gao et al, 2007). The isolate Isaria javanica pf04 was successfully cultured for virulence against second-instar whitefly nymphs using single-phase, solid-state fermentation on a barley substrate supplemented with additives that included organic silkworm powder, moth larvae, and inorganic CaCO 3 or CaSO 4 (Kim et al, 2014;Xie et al, 2016). Growth temperature was a key factor determining mycelial mass and spore production for I. fumosoroseus (Fargues and Bon, 2004).…”