Browsing by Autor "W. J. Kaiser"

Now showing 1 - 4 of 4

First Report of Botryosphaeria dothidea and B. obtusa on Apple in Bolivia
(American Phytopathological Society, 2002) W. J. Kaiser; G. M. Rivero V.; E. Valverde B.; L. Yerkes
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.
First Report of Ascochyta Blight of Chickpea in Latin America
(American Phytopathological Society, 2000) W. J. Kaiser; F. Coca W.; S. Vega O.
Chickpea (Cicer arietinum L.) has been cultivated in different regions of Bolivia for hundreds of years. In the highlands (2,400 to 3,000 m above sea level) of the Department (state) of Chuquisaca in southern Bolivia, chickpea is an important cash crop for small farmers. During March through April 1999, a blight was observed infecting local chickpea landraces in Chamicle, Escana, Kullpa Ckasa, Presto, Q'ara Puncu, Santa Rosalia, Sucre, and Yotala in Chuquisaca, and its cause was tentatively identified as Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovachevski) v. Arx) based on disease symptomatology. Stems, leaflets, and pods of infected plants exhibited abundant necrotic lesions. Isolations were made from lesions on leaflets, stems, pods, and seeds of infected plants on 2% water agar and potato dextrose agar. The fungus was isolated from the foliar and reproductive tissues of infected plants. Koch's postulates were fulfilled by inoculating the foliage of 15-day-old seedlings of a local chickpea landrace with spore suspensions of three isolates of the pathogen from Escana, Santa Rosalia, and Sucre. Inoculated and control (sterile water) plants were incubated in moist chambers for 4 days in the laboratory at ambient temperatures and under natural daylight. The fungus was reisolated from lesions that developed on the leaflets, petioles, and stems of all inoculated seedlings but not from tissues on any of the noninoculated control plants. The fungus was identified as A. rabiei based on symptoms, cultural and morphological characteristics (2), and pathogenicity tests. Above average rainfall and cool weather during March and April favored development and spread of the disease in many chickpea-growing areas. Severe infection usually resulted in dieback and death of plants and reduced yields. Additionally, A. rabiei was isolated from chickpea seeds purchased in the markets of Sucre and Monteagudo and in seeds used by farmers in Escana to plant the 1999 crop (which had supplied the plants previously observed with blight). The teleomorph did not develop on naturally infested chickpea debris from five locations when incubated over the winter on the soil surface in Sucre. Based on farmers' reports, it appears that Ascochyta blight of chickpea has been present in the Department of Chuquisaca and possibly other Bolivian departments for many years. This is the first report of the disease in either Bolivia or other countries of Latin America (Mexico and Central and South America) (1). References: (1) CAB. 1991. CAB Distribution Maps of Plant Diseases: Ascochyta rabiei. Map No. 151. CAB International Mycological Institute, Wallingford, England. (2) E. Punithalingham and P. Holliday. 1972. Ascochyta rabiei. Descriptions of Pathogenic Fungi and Bacteria No. 337. Commonwealth Mycological Institute, Kew, England.
First Report of Diplodia Cane Dieback of Grapevine in Bolivia
(American Phytopathological Society, 2009) W. J. Kaiser; G. M. Rivero V.; E. Valverde B.
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.
Occurrence of the Ascochyta blight pathogen,Ascochyta lentis, on lentil seed in Bolivia
(Springer Science+Business Media, 2007) W. J. Kaiser; G. M. Rivero; E. Valverde; L. Yerkes; Tobin L. Peever