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Previous issue date: 2010-08-25 === CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico === Guaran´a is one of the most important crops in the state of Amazonas. Commercially, their
use is as refrigerant, however, the industry of Guaran´a has been growing and diversifying its
products, including the foreign market. The main disease that affects the culture of guarana
is anthracnose, and its etiologic agent, is the pathogen Colletotrichum guaranicola. The main
form of anthracnose control is the use of chemical fungicides, but in some regions, which have
gained the recognition of organic agriculture, this control measure is not appropriate to the
needs of production. Several species of genus Trichoderma, are antagonists used effectively
in biological control of some plant pathogens, including the genus Colletotrichum. The presence
of dsRNAs is common in fungi, being reported in the literature many studies associating
them with various aspects of these hosts: hipovirulence morphological changes, the phenotype
“ killer”in yeast, and others changes in these microorganisms. The main objective of this research
was investigate the presence and influence of dsRNA on the antagonistic potential of
Trichoderma spp. against C. guaranicola. We analyzed 100 isolates of Trichoderma spp.,
and only one presented dsRNA. The species was determined by sequencing the ITS region of
rDNA and its micromorphological aspects (optical and electron microscopy) as Trichoderma
asperellum. We proceeded to purify this material by column chromatography on cellulose and
digestion with nucleases (DNase I and nuclease S1). To analyze the possible interference of
these particles in the antagonistic potential of Trichoderma, the dsRNA was eliminated with
sodium deoxycholate, added to PDA medium at a concentration of 200 mg / mL. Tests of
antagonism in vitro (by the method of pairing in Petri dishes), showed a difference between inbred
strains (with and without dsRNA) against the pathogen. In vivo tests, in plants of Mucuna
aterrima, showed no statistical difference between the isolates with and without dsRNA. Morphological
alterations were observed betweem isolates with and without dsRNA, the absence of
dsRNA showed higher mycelial growth and higher production of spores. Based on these results
it was concluded that dsRNA present in T. asperellum interfere in its potential antagonist in
vitro tests, but not to its performance in vivo tests. === O guaran´a (Paulinia cupana) ´e uma das mais importantes culturas do Estado do Amazonas.
Comercialmente, sua utilizac¸ ˜ao ´e maior nos refrigerantes gaseificados, no entanto, a
ind´ustria do guaran´a vem crescendo e diversificando seus produtos, inclusive no mercado internacional.
A principal doenc¸a que afeta a cultura do guaran´a ´e a antracnose, sendo seu
agente etiol´ogico o fitopat´ogeno Colletotrichum guaranicola. A principal forma de controle
da antracnose ´e o emprego de fungicidas qu´ımicos, por´em, em algumas regi˜oes, que adquiriram
o reconhecimento de cultura orgˆanica, esta medida de controle n˜ao se adequa `as necessidades
da produc¸ ˜ao. As esp´ecies do gˆenero Trichoderma, s˜ao antagonistas utilizadas eficazmente
no controle biol´ogico de algumas esp´ecies fitopatogˆenicas, incluindo o gˆenero Colletotrichum.
A presenc¸a de dsRNAs ´e frequente em fungos, sendo relatada na literatura muitas pesquisas
associando-os com v´arios aspectos nestes hospedeiros: fen´otipos hipovirulentos, alterac¸ ˜oes
morfol´ogicas, o fen´otipo “killer” em leveduras, ou ainda, a nenhuma alterac¸ ˜ao nestes microrganismos.
Esta pesquisa teve por objetivos investigar a presenc¸a e influˆencia de dsRNA sobre o
potencial antagˆonico de Trichoderma spp. contra C. guaranicola. Foram analisados 100 isolados
de Trichoderma spp., sendo que apenas um apresentou dsRNA. A esp´ecie foi determinada
por sequenciamento da regi˜ao ITS do rDNA e seus aspectos micromorfol´ogicos (microscopia
´optica e eletrˆonica de varredura) como Trichoderma asperellum. Procedeu-se a purificac¸ ˜ao
deste material por meio de cromatografia em coluna de celulose e a digest˜ao com nucleases
(DNAse I e nuclease S1). Para analisar a poss´ıvel interferˆencia destas part´ıculas no potencial
antagˆonico dos isolados de Trichoderma, eliminou-se o dsRNA do isolado infectado com a
substˆancia desoxicolato de s´odio, adicionada ao meio BDA na concentrac¸ ˜ao de 200 mg/mL.
Testes de antagonismo in vitro (pelo m´etodo de pareamento em placa), revelaram diferenc¸a
entre as linhagens is´ogenas (com e sem dsRNA) contra o fitopat´ogeno. O teste in vivo, pelo
m´etodo de adic¸ ˜ao de esporos de antagonista e fitopat´ogenos em plantas de Mucuna aterrima,
n˜ao apresentou diferenc¸a estat´ıstica entre as li-nhagens. Morfologicamente houve alterac¸ ˜oes
entre os isolados com e sem dsRNA, sendo que os sem dsRNA, apresentaram maior crescimento
micelial e maior produc¸ ˜ao de esporos. Diante dos resultados obtidos concluiu-se que o
dsRNA presente em T. asperellum interfere no seu potencial antagonista em testes in vitro, mas
n˜ao no seu desempenho em testes in vivo.
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