Conidial Production on Different Solid Substrates and Pathogenicity ofHirsutella citriformisAgainstDiaphorina citriAdults

Abstract

Conidia of four strains of H. citriformis Speare fungi grown on oat (Avena sativa L.), wheat (Triticum aestivum L.), and sorghum (Sorghum bicolor (L.) Moench) were evaluated for production and for viability and pathogenicity against D. citri Kuwayama adults. Substrates were inoculated with conidial suspensions (1 × 106 conidia/ml) of INIFAP-Hir-1, INIFAP-Hir-2, IB-Hir-1, and IB-Hir-2 strains and incubated for 35 days. Pathogenicity on Asian citrus psyllid adults also was evaluated through contact bioassay. Significantly more conidia were produced on oat (58.5-28.83 × 106 per gram) than wheat (50.9-29.4 × 106 per gram) at 21 days. Production of most conidia (8.4-6.6 × 106 per gram) required 28 days on sorghum and was less than on oat or wheat. Percentages of germination of conidia on the three substrates ranged from 96.25 to 98.0% without significant differences among them. Pathogenicity of the strains against Asian citrus psyllid were not significantly different when grown on agar (85.5–89.9%) or oat (85.8–89.3%). Results confirmed the possibility of increased production of H. citriformis conidia in natural substrates maintaining pathogenicity against Asian citrus psyllid.