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Botrytis cinerea isolates collected from grapes present different requirements for conidia germination

     Facultad de Química y Biología, Universidad de Santiago de Chile (USACH), Casilla 40-Correo 33, Santiago-Chile

Botrytis cinerea presents high variability in several biological traits, which can be explained by the high degree of genotypic diversity among isolates. Because this genetic variability might be related to phenotypic differences the requirements for conidia germination of three natural isolates (G1, G5 and G11) obtained from grapes and belonging to the same genetic group were analyzed. The results showed that contact with a solid surface was a common requisite for conidia germination of the isolates but they differed in their nutritional requirements to germinate. Isolate G11 was able to germinate in the absence of a carbon or nitrogen source. G1 and G5 required the presence of a carbon source such as glucose, fructose or sucrose. In G11 and G5 isolates a much higher rate of germination was obtained in the presence of sucrose.

It was shown with a pharmacological approach that the cAMP stimulated the germination only in those isolates requiring a carbon source. Conidia germination of G1 and G5 was inhibited by EGTA, a calcium chelator. Isolate G11 germinated in the presence of this compound. On the other hand the germination of three B. cinerea isolates required protein synthesis and did not require RNA synthesis. To explain the ability of isolate G11 to germinate in water the content of total and reducing sugars, mannitol/L-arabitol, trehalose, and proteins in the nongerminated conidia of the three isolates was compared. The isolates presented similar amounts of total and reducing sugars. In the three isolates the amount of mannitol/L-arabitol was higher than that of trehalose. In isolate G11 total protein content was twice higher than in the other isolates.

Key words: Botrytis cinerea, cAMP, conidia germination, gray mold, polyol, protein pool, trehalose