Coertze Sonja, Holz Gustav
Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
Plant Dis. 1999 Oct;83(10):917-924. doi: 10.1094/PDIS.1999.83.10.917.
Infection of grapes by different densities of airborne conidia of Botrytis cinerea was investigated on table grapes (cultivar Dauphine) harvested ripe (16°Brix) and inoculated fresh, or after SO treatment and 8-week storage at -0.5°C. Berries were detached at each inoculation and dusted with dry conidia in a settling tower. Following inoculation, the fresh berries were incubated for 24 h at high relative humidity (≥93%), or were overlaid with wet sterile paper towels. Cold-stored berries were incubated at high relative humidity. The effect of conidial density on surface colonization, penetration, and lesion formation was determined by surface sterilization, isolation, and freezing studies on fresh berries. Only symptom expression was determined on cold-stored berries. Fluorescence microscopy of skin segments showed that conidia were consistently deposited as single cells, and not in pairs or groups, on berry surfaces. Individual conidia, at all densities tested, readily infected the cold-stored berries and formed separate lesions after 2 days. Although the cold-stored berries were highly susceptible, lesion numbers were not related to conidial density at low inoculum dosages (0.67 to 2.60 conidia per mm berry surface). Lesion numbers tended to increase exponentially at higher dosages (3.24 to 3.88 conidia per mm berry surface). Individual conidia, however, did not induce any disease symptoms on fresh berries. Removal of the pathogen after 24-h incubation from the surface of fresh berries by ethanol, and subsequent incubation of excised skin segments revealed that, irrespective of the conidial density or the wetness regime, less than 2% of skin segments were penetrated. Furthermore, increasing densities of conidia did not lead to higher rates of surface colonization and skin penetration. The low incidence of disease caused on fresh berries and high disease incidence induced after prolonged cold storage indicated that infection was not governed by conidial density on berry surfaces, but by the level of host resistance.
研究了不同密度的灰葡萄孢气传分生孢子对鲜食葡萄（品种为多芬）的侵染情况。葡萄成熟时（糖度16°Brix）采收，或经二氧化硫处理并在-0.5°C下储存8周后新鲜接种。每次接种时将浆果摘下，在沉降塔中用干分生孢子进行喷粉处理。接种后，新鲜浆果在高相对湿度（≥93%）下孵育24小时，或用湿无菌纸巾覆盖。冷藏的浆果在高相对湿度下孵育。通过对新鲜浆果进行表面消毒、分离和冷冻研究，确定分生孢子密度对表面定殖、穿透和病斑形成的影响。对于冷藏的浆果，仅测定症状表现。对果皮切片进行荧光显微镜观察表明，分生孢子在浆果表面始终以单细胞形式沉积，而非成对或成组沉积。在所有测试密度下，单个分生孢子都能轻易感染冷藏的浆果，并在2天后形成单独的病斑。尽管冷藏的浆果高度易感，但在低接种剂量（每平方毫米浆果表面0.67至2.60个分生孢子）下，病斑数量与分生孢子密度无关。在较高剂量（每平方毫米浆果表面3.24至3.88个分生孢子）下，病斑数量趋于呈指数增加。然而，单个分生孢子在新鲜浆果上并未引发任何病害症状。通过乙醇在新鲜浆果表面孵育24小时后去除病原体，随后对切下的果皮切片进行孵育，结果表明，无论分生孢子密度或湿度条件如何，穿透的果皮切片不到2%。此外，分生孢子密度的增加并未导致更高的表面定殖率和果皮穿透率。新鲜浆果上病害发生率低，而长期冷藏后病害发生率高，这表明感染并非由浆果表面的分生孢子密度决定，而是由宿主抗性水平决定。
