Roggero P, Melani V, Ciuffo M, Tavella L, Tedeschi R, Stravato V M
Istituto di Fitovirologia Applicata, CNR, Str. delle Cacce 73, I-10135 Torino, Italy.
Di.Va.P.R.A. Entomologia e Zoologia Applicate all' Ambiente "C. Vidano," Università, Via L. da Vinci 44, I-10095 Grugliasco, Torino, Italy.
Plant Dis. 1999 Oct;83(10):965. doi: 10.1094/PDIS.1999.83.10.965A.
The hypersensitive response to tomato spotted wilt tospovirus (TSWV) present in Capsicum chinense PI152225 (1) was introgressed into C. annuum cultivars. During the summer of 1998, a hybrid with good agronomic performance was grown in glasshouses in Albenga, Liguzia Region of northwestern Italy, an area where infection by TSWV in pepper has been severe since 1992. In August, observations of different susceptible cultivars revealed that >50% of plants had TSWV-like symptoms, whereas the resistant hybrid remained healthy, except for two plants that showed virus-like symptoms on apical leaves and fruits. From the infected plants, tospoviruses (coded P164/6 and P166) were transmitted by sap-inoculation to Nicotiana benthamiana. Triple-antibody sandwich enzyme-linked immunosorbent assay with a panel of monoclonal antibodies against the TSWV nucleocapsid, but with different reactivity to the related species groundnut ringspot (GRSV) and tomato chlorotic spot (TCSV) viruses, indicated the isolates were TSWV. The host ranges of the isolates were wide and typical of normal TSWV isolates. Thus, they incited typical symptoms in all 50 TSWV-susceptible C. annuum cv. Quadrato d'Asti plants. However, isolate P164/6 also systemically infected 12 of 27 C. chinense PI152225 and 14 of 19 C. chinense PI159236 plants. These accessions are normally resistant to TSWV (1). Isolate P166 systemically infected 7 of 17 C. chinense PI152225 and 6 of 11 C. chinense PI159236 plants. Systemically infected plants showed severe necrosis, and some plants died. Other plants showed only necrotic local lesions. The response by C. chinense differed from that caused by typical TSWV, which causes only local lesions, and from both GRSV and TCSV, which cause mosaic but no necrosis in 100% of plants. The two new TSWV isolates were tested for transmission using a local population of Frankliniella occidentalis in a leaf disk assay with susceptible C. annuum. Transmission rates were high: 93.7% (63 thrips) for isolate P164/6 and 89.9% (49 thrips) for P166. Thus, the fitness of the two TSWV resistance-breaking isolates (a wide experimental host range and high transmission rates by the natural vector) was as high as that of typical TSWV. The absence of systemic infection in some C. chinense PI152225 and PI159236 plants that are resistant to typical TSWV suggests the possibility of selecting plants resistant to these pathotypes. This is the first report of field tospovirus isolates typed as TSWV (according to the current taxonomy based on nucleocapsid serology) overcoming the hypersensitive response of C. chinense PI152225 and PI159236, an ability previously found only in closely related viruses: TCSV and GRSV (2). Other TSWV-like isolates systemic on C. chinense were not typed further (3,4). References: (1) L. L. Black et al. Plant Dis. 75:863, 1991. (2) L. S. Boiteux and A. C. DeAvila. Euphytica 75:139, 1994. (3) H. A. Hobbs et al. Plant Dis. 78:1220, 1994. (4) B. Moury et al. Euphytica 94:45, 1997.
辣椒PI152225（1）对番茄斑萎病毒（TSWV）的过敏反应被导入到辣椒栽培品种中。1998年夏季，一个农艺性状优良的杂交种在意大利西北部利古里亚地区阿尔本加的温室中种植，自1992年以来该地区辣椒受TSWV感染严重。8月，对不同感病品种的观察发现，超过50%的植株有TSWV样症状，而抗性杂交种保持健康，只有两株植株顶端叶片和果实出现病毒样症状。从感染植株上，通过汁液接种将番茄斑萎病毒（编号P164/6和P166）传播到本氏烟草。用一组针对TSWV核衣壳的单克隆抗体进行的三抗体夹心酶联免疫吸附测定，但对相关种花生环斑病毒（GRSV）和番茄褪绿斑病毒（TCSV）病毒有不同反应性，表明分离物为TSWV。这些分离物的寄主范围广泛，是正常TSWV分离物的典型特征。因此，它们在所有50株感TSWV的辣椒品种“阿斯蒂方块”植株上引发了典型症状。然而，分离物P164/6也系统感染了27株辣椒PI152225中的12株和19株辣椒PI159236中的14株。这些种质通常对TSWV具有抗性（1）。分离物P166系统感染了17株辣椒PI152225中的7株和11株辣椒PI159236中的6株。系统感染的植株出现严重坏死，一些植株死亡。其他植株仅出现坏死局部病斑。辣椒的反应不同于典型TSWV引起的反应，典型TSWV仅引起局部病斑，也不同于GRSV和TCSV，GRSV和TCSV在100%的植株中引起花叶但无坏死。使用西花蓟马当地种群在感病辣椒的叶盘试验中对这两个新的TSWV分离物进行传播测试。传播率很高：分离物P164/6为93.7%（63只蓟马），P166为89.9%（49只蓟马）。因此，这两个打破TSWV抗性的分离物（广泛的实验寄主范围和自然传播介体的高传播率）的适合度与典型TSWV一样高。一些对典型TSWV具有抗性的辣椒PI152225和PI159236植株未出现系统感染，这表明有可能筛选出对这些致病型具有抗性的植株。这是首次报道田间番茄斑萎病毒分离物（根据基于核衣壳血清学的当前分类法归类为TSWV）克服了辣椒PI152225和PI159236的过敏反应，此前仅在密切相关病毒TCSV和GRSV中发现这种能力（2）。其他在辣椒上系统感染的TSWV样分离物未作进一步分类（3,4）。参考文献：（1）L.L.布莱克等人，《植物病害》75:863，1991。（2）L.S.博特克斯和A.C.德阿维拉，《欧洲植物病理学报》75:139，1994。（3）H.A.霍布斯等人，《植物病害》78:1220，1994。（4）B.穆里等人，《欧洲植物病理学报》94:45，1997。
