Severe Outbreaks of Bunch Rots Caused by Rhizopus stolonifer and Aspergillus niger on Table Grapes in Chile

Plant Disease
B A LatorreI Spadaro

Abstract

Severe outbreaks of bunch rots (BR) have occurred recently during harvest of table grapes (Vitis vinifera L.) in Chile. Previously, BR was almost exclusively associated with Botrytis cinerea Pers.:Fr. (2,3); however, in 2000 to 2002, BR symptoms were associated with black molds and possibly nonfilamentous yeasts and bacteria. Cvs. Thompson Seedless, Flame Seedless, Ruby Seedless, and Red Globe were severely affected. Symptoms start at the pedicels as soft, watery rots that partially or completely decay infected berries. Longitudinal cracks are produced, a black mold usually develops along the crack fissures, and the skin of the berry turns light gray. Isolations on potato dextrose agar acidified with 1 N lactic acid (APDA) at 0.5 ml/liter, consistently yielded Rhizopus stolonifer (Ehrenb. ex Fr.) Vuillemin and Aspergillus niger Tiegh. R. stolonifer on APDA produced a white-to-gray aerial and nonseptate mycelium, black and globose sporangia with an elliptical collumela, one-celled, globose to oval, striated, almost hyaline sporangiospores, rhizoids, and stolons. A. niger produced septate mycelium. Single-celled, black, rough walled, globose conidia developed on short chains on the second phialides at the tip of globose, upright ...Continue Reading

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