Ks. Elias et Pj. Cotty, INCIDENCE AND STABILITY OF INFECTION BY DOUBLE-STRANDED-RNA GENETIC ELEMENTS IN ASPERGILLUS SECTION FLAVI AND EFFECTS ON AFLATOXIGENICITY, Canadian journal of botany, 74(5), 1996, pp. 716-725
Ninety-two isolates belonging to Aspergillus sect. flavi were analyzed
for double-stranded (ds) RNA via standard cellulose chromatography. D
ouble-stranded RNA infection was detected in fungal isolates that had
been in culture for long periods (5 of 26 were infected) and in those
recently isolated (5 of 66 were infected). The number of dsRNA genetic
elements differed among infected isolates and no two isolates contain
ed identical dsRNAs on the basis of electrophoretic migration in agaro
se gels. Addition of micronutrients to culture media affected both the
amount of dsRNA produced and the number of dsRNA genetic elements det
ected. Attempts to cure six fungal isolates of dsRNA by serial single
conidial transfer, chlorate selection for nitrogen-metabolism mutants,
and cycloheximide treatment, met with variable results. The frequency
at which serial single conidial transfer and nitrogen-metabolism muta
nt (nit) selection successfully cured six Aspergillus sect. flavi isol
ates varied from 11 to 100% and 0 to 100%, respectively. The cyclohexi
mide treatment was effective at curing 40% of the dsRNA-infected isola
tes. Comparison of aflatoxin production prior to and after dsRNA curin
g indicated that infection by dsRNA did not influence aflatoxin produc
tion. However, aflatoxin production by two isolates (91-031B and 91-18
4G) was reduced by both single conidial transfer and induction of nit
mutants.