Selection and caracterization of Metarhizium anisopliae for the control of Mahanarva fimbriolata (Hemiptera: Cercopidae) in sugar-cane. / Seleção e caracterização de Metarhizium anisopliae visando ao controle de Mahanarva fimbriolata (Hemiptera: Cercopidae) em cana-de-açúcar.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This research was carried out to evaluate the pathogenicity of isolates of the entomopatogenic fungus Metarhizium anisopliae against the spittlebug, Mahanarva fimbriolata, and to characterize them morphologically and genetically through RAPD method. The selection was made under laboratory condition, using nymphs collected at field. The fungus was sprayed on the nymphs by a Potter tower (15 pounds/pol2) and then, they were maintained in roots of sugar-cane seedlings. The mortality was evaluated 5 days after the inoculation, ranging from 10.5 to 60%. The colonies’ color varied from grayish green to dark green and the colonies diameter ranged from 28mm (isolate IBCB-353) to 38mm (isolate IBCB-348). The conidia length ranged from 5.465µm for the isolate IBCB-345 to 7.970µm for the isolate ESALQ 1301. With those results it could be concluded that all the studied strains belong to the subspecies anisopliae. The size did not have influence in the pathogenicity of the isolate. It was evidenced presence of double-stranded RNA (virus) in eleven out of the twenty isolates tested, but it did not have relation between the presence of the virus and its pathogenicity for M. fimbriolata. It was possible to separate isolates in two groups (A and B) with 72.5% of similarity, being observed the composition of two sub-groups (B1 and B2), with 77.5% of similarity, inside of group B. The high similarity between the two groups and inside of each one indicated that the isolates belong to the same subspecies, confirming what it was concluded with the morphologic characterization. The used method confirms the great genetic diversity of species M. anisopliae, however, does not reflect its similarity of pathogenicity the nymphs of M. fimbriolata, therefore the two isolated most pathogenic (IBCB-384 and ICBC-348) were located in different fenetic groups. In the present study a specific standard of grouping between isolated deriving of the same region or host was not observed, or either, the genetic diversity seems to be independent on the fungus origin, as it would be expected from a pathogen that, in general, shows high degree of specialization to the host.

ASSUNTO(S)

entomopathogenic fungi molecular marker diversidade genética biological control dna marcador molecular sugar-cane dna spittlebug cigarrinha-da-raiz cana-de-açúcar fungo entomopatogênico genetic diversity controle biológico (fitossanidade)

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