Characterization of Brazilian Cordyceps fumosorosea isolates: Conidial production, tolerance to ultraviolet-B radiation, and elevated temperature.

Cordyceps fumosorosea is an entomopathogenic fungus with a global distribution and is used for the biological control of agricultural pests. High conidial productivity and tolerance to abiotic stresses such as elevated temperature and ultraviolet radiation (UV-B) are desired characteristics in candidate isolates for commercial products. Our goal in this study was to characterize promising isolates of C. fumosorosea from five Brazilian biomes regarding conidial production, tolerance to UV-B, and elevated temperature (45°). Seventy-two isolates out of 172 were chosen visually, based on growth and sporulation in culture medium, and grown on parboiled rice. Next, fourteen isolates were selected, based on productivity on rice and origin of isolation, for production in polypropylene bags and submitted to UV-B for 2, 4, 6, and 8 h or to 45 °C for 30, 60, and 90 min. High variations in conidial production were observed among isolates, and a positive correlation was observed between UV-B and heat tolerance. The isolates ESALQ4556 and ESALQ4778 showed the highest yields of conidial production in polypropylene bags (3.51 × 109 conidia/g dry rice), while ESALQ1296, an isolate recovered from insects, was the most tolerant to UV-B and 45 °C. Exposure to radiation for more than 4 h and placed directly at 45 °C for more than 30 min significantly reduced conidial germination for all C. fumosorosea isolates. These results contribute to a better understanding of the tolerance to abiotic factors of Brazilian isolates of C. fumosorosea.

Interactions of adjuvants on adhesion and germination of Isaria fumosorosea on adults of Diaphorina citri

Asian citrus psyllid, Diaphorina citri, is considered the most important citrus pest worldwide, as it transmits Huanglongbing – serious citrus disease. New efficient and sustainable strategies to control this pest have been investigated and the use of entomopathogenic fungi has become a promising alternative. The objective of this study was to evaluate the effects of adjuvants a) Tween 80 at 0.01 % (v/v); b) Silwet L77 at 0.025 % (v/v) and c) KBRAdj at 0.075 % (v/v) on adhesion, germination and pathogenicity of Isaria fumosorosea ESALQ-1296(5 × 106 conidia mL–1). Female adults of D. citri used in this experiment were sprayed on Citrus limonia seedlings. The sprayed insects were analyzed through scanning electron microscopy (SEM) to identify the most susceptible integument regions for fungus attachment and the effect of adjuvants used. In the pathogenicity test, adjuvants Silwet L77 and KBRAdj presented a higher efficiency than Tween 80. Fungi adhered predominantly to the ventral posterior (abdomen) region in comparison with the dorsal anterior (thorax) region. In addition, adjuvants Silwet L77 and KBRAdj presented faster germination ( 72 h). Conidial germination in the dorsal part of the thorax of the insects was observed only with adjuvant KBRAdj 72 h post inoculation.

Interactions of adjuvants on adhesion and germination of Isaria fumosorosea on adults of Diaphorina citri

Asian citrus psyllid, Diaphorina citri, is considered the most important citrus pest worldwide, as it transmits Huanglongbing serious citrus disease. New efficient and sustainable strategies to control this pest have been investigated and the use of entomopathogenic fungi has become a promising alternative. The objective of this study was to evaluate the effects of adjuvants a) Tween 80 at 0.01 % (v/v); b) Silwet L77 at 0.025 % (v/v) and c) KBRAdj at 0.075 % (v/v) on adhesion, germination and pathogenicity of Isaria fumosorosea ESALQ-1296(5 × 106 conidia mL–1). Female adults of D. citri used in this experiment were sprayed on Citrus limonia seedlings. The sprayed insects were analyzed through scanning electron microscopy (SEM) to identify the most susceptible integument regions for fungus attachment and the effect of adjuvants used. In the pathogenicity test, adjuvants Silwet L77 and KBRAdj presented a higher efficiency than Tween 80. Fungi adhered predominantly to the ventral posterior (abdomen) region in comparison with the dorsal anterior (thorax) region. In addition, adjuvants Silwet L77 and KBRAdj presented faster germination (< 48 h) of I. fumosorosea spores when compared to Tween 80 (> 72 h). Conidial germination in the dorsal part of the thorax of the insects was observed only with adjuvant KBRAdj 72 h post inoculation.(AU)