RESUMO
Grape (Vitis vinifera L.) is an important commercial crop in the temperate regions of Bolivia where it has been grown for hundreds of years. In October of 2001, diseased canes of grape (cv. Muscat of Alexandria) were collected in a vineyard in Yotala, Department of Chuquisaca in southern Bolivia. In this planting of more than 1,000 plants, more than 75% were exhibiting cane dieback symptoms and many were dead or dying. No disease was observed on grape berries. Symptoms of the disease were similar to those reported for Diplodia cane dieback (1). Cankers ranging from 2 to 10 cm long and 0.5 to 3 cm wide were observed. When diseased canes were placed in a moist chamber, conidia oozed from pycnidia in black cirri. Immature conidia were hyaline and one-celled, but mature conidia were dark brown (20 to 30 × 10 to 15 µm) with one median septum and longitudinal striations. The pathogen was tentatively identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (synonyms Diplodia natalensis Pole-Evans and Botryodiplodia theobromae Pat.), teleomorph Botryosphaeria rhodina (Cooke) Arx) (2). Fungi were isolated from cankers on diseased canes by surface disinfestation in 0.25% NaOCl for 5 min and placing small pieces of tissue on 2% water agar or potato dextrose agar (PDA). L. theobromae was isolated from these tissues. Koch's postulates were fulfilled by inoculating grape berries and canes with the pathogen. Five grape berries were surface disinfested and inoculated by wounding with a sterile scalpel and inserting a piece of fungal mycelium on PDA in the wounded sites. The same number of control berries was similarly treated with sterile PDA. Inoculated and control berries were placed in plastic, moist chambers in the laboratory at ambient temperature (15 to 28°C) in the dark. Five canes on two potted plants were inoculated with the same isolate of the pathogen in a similar manner as the berries. The inoculated and control sites on canes were wrapped with masking tape. Plants were placed in a moist chamber for 5 days. After 8 days, inoculated berries were rotting and the inoculated sites were covered with grayish mycelium. Within 12 days, cankers as much as 3 cm long developed on the inoculated canes, and in some lesions, black pycnidia were observed. No lesions developed in the wounded control canes. The pathogen was reisolated from inoculated berries and canes, but not from control berries or canes. The teleomorph was not observed on any naturally infected canes or on those inoculated with the anamorph. The pathogen was identified as L. theobromae based on symptoms (1), cultural and morphological characteristics (2), and pathogenicity tests. The disease poses a potential threat to the cultivation of grapevine in southern Bolivia. To our knowledge, this is the first report of Diplodia cane dieback of grapevine in Bolivia. References: R. C. Pearson and A. C. Goheen. Compendium of Grape Diseases. The American Phytopathological Society, St. Paul, MN, 1988. (2). E. Punithalingam. No. 519 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, England, 1976.
RESUMO
Gala and Winter Banana apples are important commercial crops in Azurduy and Lima Bamba, which are located in the Department (state) of Chuquisaca, Bolivia. White or bot rot (causal agent Botryosphaeria dothidea (Moug.:Fr.) Ces. De. Not. [anamorph Fusicoccum aesculi Corda]) and black rot (causal agent B. obtusa (Schwein.) Shoemaker [anamorph Sphaeropsis malorum Berk.]) have not been reported previously from Bolivia. Both fungi were isolated from apple fruit and branch cankers in Azurduy, but only B. dothidea was isolated from rotted fruit and limb cankers in Lima Bamba. Both fungi also were isolated from rotted Gala and Winter Banana fruit purchased in the markets in Sucre, Bolivia. Symptoms on fruit consisted of light-to-dark brown lesions that ranged from 3- to 8-cm in diameter. Cankers on limbs were sunken and reddish brown and ranged from 2 to 25+ cm in length and 0.5 to 3 cm in diameter. Neither pathogen produced pycnidia in lesions on rotted fruit, but they often developed in branch cankers. Pseudothecia of B. dothidea and B. obtusa were not observed. Identification of both pathogens was based on descriptions of their anamorphic stages (1). To fulfill Koch's postulates, four healthy Gala apple fruit were inoculated with two isolates of each pathogen by wounding the opposite faces of surface-disinfected fruit with a 5-mm-diameter cork borer and inserting mycelial plugs of the pathogens. Plugs were obtained from the margins of cultures growing on potato dextrose agar (PDA). Wounds were made on the opposite sides of each fruit, a mycelial plug of one of the pathogens was inserted in one wound, and on the opposite side, a plug of sterile PDA was inserted as a control. Each plug containing fungal mycelium or sterile PDA was covered with a plug of trimmed apple tissue, and the apple fruit were incubated in a moist chamber at 17 to 20°C for 10 days. Six branches on two young apple trees growing outdoors in a nursery were inoculated in a similar manner with one isolate of each pathogen: bark was wounded with a 5-mm-diameter cork borer, and the wounded area was inoculated with a plug of PDA containing the pathogen or a plug of sterile PDA for the control. The inoculated sites were wrapped with masking tape to prevent dehydration. Within 10 days, all fruit wounds inoculated with isolates of each pathogen developed brown lesions up to 5 cm in diameter. Each pathogen was reisolated from tissues in which it had been inoculated, but not from any of the noninoculated control sites. Within 6 to 8 weeks, all but one wound on branches inoculated with each pathogen developed depressed canker lesions up to 2 cm in length. Each pathogen was reisolated from the canker produced by inoculation with that pathogen, but not from any of the control sites. Reference: (1) T. B. Sutton. White rot and black rot. Pages 16-20 in: Compendium of Apple and Pear Diseases, A. L. Jones and H. S. Aldwinckle, eds. The American Phytopathological Society, St. Paul, MN, 1991.
