Polizzi G, Aiello D, Castello I, Guarnaccia V, Vitale A
Dipartimento di Scienze e Tecnologie Fitosanitarie, University of Catania, Via S. Sofia 100, 95123 Catania, Italy.
Plant Dis. 2010 Apr;94(4):486. doi: 10.1094/PDIS-94-4-0486B.
Marmalade bush (Streptosolen jamesonii (Benth.) Miers), also known as fire bush, is an evergreen, perennial shrub in the family Solanaceae, which is native to South America (Colombia, Ecuador, and Peru). In Italy, this species is cultivated as an ornamental creeper or bush. During September 2009, a new disease was observed in a stock of ~10,000 pot-grown, 2-month-old plants of marmalade bush in a nursery in eastern Sicily, Italy. More than 50% of the plants exhibited symptoms of disease. Disease symptoms consisted of extensive water-soaked, dark brown lesions at the crown level that girdled entire stems and an internal brown discoloration of cortical tissue. Infected plants died within a few days. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/liter. Fungal colonies were initially white, turned brown after 2 to 3 days, and produced irregularly shaped, brown sclerotia. Microscopic examination showed mycelium consistent with Rhizoctonia solani Kühn that branched at right angles, constricted at the base of the branch originating from primary hyphae, and septate near the constriction. The number of nuclei per hyphal cell was determined on cultures grown at 25°C on 2% water agar in petri plates by staining with 1% safranin O and 3% KOH solution (1) and examined at ×400. The hyphal cells were all multinucleate. Anastomosis group was determined by pairing isolates on 2% water agar in petri plates (2). Pairings were made with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4. Pathogenicity tests were performed by placing 1-cm plugs of PDA from 5-day-old mycelial cultures near the base of the stem on 25 potted, healthy, 2-month-old rooted cuttings of marmalade bush. The same number of plants treated with 1-cm PDA plugs served as controls. Following inoculation, all plants were maintained for 20 days at 25°C and 95% relative humidity under a 12-h fluorescent light/dark regimen. Crown and stem symptoms, identical to those observed in the nursery, developed 5 days after inoculation on all inoculated plants. Control plants remained symptomless. R. solani was consistently reisolated from symptomatic tissues and identified as previously described. To our knowledge, this is the first report of R. solani causing disease on marmalade bush. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.
金橘树（Streptosolen jamesonii (Benth.) Miers），也被称为火焰树，是茄科的一种常绿多年生灌木，原产于南美洲（哥伦比亚、厄瓜多尔和秘鲁）。在意大利，该物种作为观赏藤蔓植物或灌木进行种植。2009年9月，在意大利西西里岛东部一家苗圃中，约10000株盆栽、2个月大的金橘树苗木中发现了一种新病害。超过50%的植株表现出病害症状。病害症状包括在植株基部出现大面积水渍状、深褐色病斑，环绕整个茎干，以及皮层组织内部呈褐色变色。受感染植株在几天内死亡。将患病组织在1%次氯酸钠中消毒10秒，用无菌水冲洗，然后接种在添加了100毫克/升硫酸链霉素的马铃薯葡萄糖琼脂（PDA）平板上。真菌菌落最初为白色，2至3天后变为褐色，并产生不规则形状的褐色菌核。显微镜检查显示菌丝体与立枯丝核菌（Rhizoctonia solani Kühn）一致，呈直角分枝，在源自初生菌丝的分枝基部缢缩，在缢缩处附近有隔膜。通过用1%番红O和3%氢氧化钾溶液对在25℃下于培养皿中2%水琼脂上生长的培养物进行染色（1），并在400倍下检查，确定每个菌丝细胞的核数。菌丝细胞均为多核。通过在培养皿中的2%水琼脂上配对分离物来确定融合群（2）。与测试菌株AG-1 IA、AG-2-2-1、AG-2-2IIIB、AG-2-2IV、AG-3、AG-4、AG-5、AG-6和AG-11进行配对。仅在AG-4测试分离物中观察到融合现象。通过将来自5天龄菌丝体培养物的1厘米PDA菌块放置在25株健康、2个月大的金橘树生根插条茎基部附近进行致病性测试。用相同数量的经1厘米PDA菌块处理的植株作为对照。接种后，所有植株在25℃、相对湿度95%、12小时荧光光照/黑暗周期条件下保持20天。接种后5天，所有接种植株出现与苗圃中观察到的相同的冠部和茎部症状。对照植株无症状。立枯丝核菌始终能从有症状的组织中重新分离出来，并如前所述进行鉴定。据我们所知，这是立枯丝核菌引起金橘树病害的首次报道。参考文献：（1）R. J. Bandoni。《真菌学》7:873，1979。（2）C. C. Tu和J. W. Kimbrough。《真菌学》65:941，1973。
