Barboza E A, Cabral C S, Gonçalves A M, Reis A, Fonseca M E N, Boiteux L S
Universidade de Brasília (UnB) Dept. Fitopatologia,70910-900, Brasília-DF, Brazil.
Embrapa Hortaliças (CNPH), CP 218, 70359-970, Brasília-DF, Brazil.
Plant Dis. 2013 Mar;97(3):422. doi: 10.1094/PDIS-08-12-0779-PDN.
The three races of Fusarium oxysporum f. sp. lycopersici (FOL) are important tomato pathogens throughout the world, causing severe economic losses (1). In Brazil, races 1 and 2 are widespread, but the current geographic distribution of race 3 is restricted to the mild climate areas of Espírito Santo and Rio de Janeiro States in the southeast region (2,3). Here we report the spread of FOL race 3 to the warm northeast region of Brazil. Plants in commercial fields of the hybrid 'Alambra' (resistant to FOL races 1 and 2) were found displaying chlorosis, vascular browning, and wilt symptoms in Jaguaquara County, Bahia State, Brazil. Disease incidence ranged from 10 to 50%. The virulence profile of six isolates obtained from three distinct tomato-producing fields was investigated by root-dipping inoculation (10 conidia/ml) of 21-day-old seedlings from a set of FOL race differential accessions: 'Ponderosa' (susceptible to all races), 'IPA-5' (FOL race 1 resistance; I-1 locus); 'Alambra' and 'Floradade' (FOL races 1 and 2 resistance; I-2 gene), and Solanum pennellii 'LA 716' (resistant to all three races; I-3 locus). All six isolates were able to induce severe wilt symptoms in 100% of the plants from all lines but S. pennellii 'LA 716'. FOL race 3 identity was confirmed via PCR assays employing a specific set of primers that are able to discriminate all the three FOL races as well as F. oxysporum f. sp. radicis-lycopersici isolates (1). Total DNA was extracted from pure fungal colonies growing in agar medium. The typical FOL race 3 amplicon profiles (i.e. positive for the primers uni, sp13, and sp23 and negative for the primer sprl) were observed only in the six FOL 3 isolates from Bahia as well as in five reference isolates of race 3 (previously obtained from tomato in Espírito Santo and Rio de Janeiro States), thus confirming their race identities. This recent, fast, and wide geographic expansion of the FOL race 3 in Brazil suggests that the pathogen has been introduced into new tomato producing areas via either contaminated seeds or seedlings. Because of the complexity of establishing effective chemical and cultural control strategies, these epidemics caused by FOL race 3 in distinct areas of Brazil might cause the replacement of the currently grown susceptible hybrids by resistant ones. References: (1) Y. Hirano and T. Arie. J. Gen. Plant Pathol. 72:273, 2006; (2) A. Reis et al. Fitopatol. Bras. 30:426, 2005; (3) A. Reis and L. S. Boiteux. Hort. Bras. 25:451, 2007.
尖孢镰刀菌番茄专化型（FOL）的三个生理小种是全球重要的番茄病原菌，会造成严重的经济损失（1）。在巴西，1号和2号生理小种广泛分布，但3号生理小种目前的地理分布仅限于东南部地区圣埃斯皮里图州和里约热内卢州的温和气候区（2,3）。在此，我们报告了FOL 3号生理小种已传播至巴西温暖的东北部地区。在巴西巴伊亚州雅瓜夸拉县，发现杂交种‘阿拉姆布拉’（对FOL 1号和2号生理小种具有抗性）的商业种植田中，植株出现黄化、维管束褐变和萎蔫症状。发病率在10%至50%之间。通过对一组FOL生理小种鉴别种质的21日龄幼苗进行浸根接种（10个分生孢子/毫升），研究了从三个不同番茄种植田分离得到的六个菌株的毒力谱：‘邦德罗萨’（对所有生理小种敏感）、‘IPA - 5’（对FOL 1号生理小种具有抗性；I - 1位点）、‘阿拉姆布拉’和‘弗洛拉达德’（对FOL 1号和2号生理小种具有抗性；I - 2基因），以及潘那利番茄‘LA 716’（对所有三个生理小种均具有抗性；I - 3位点）。除了潘那利番茄‘LA 716’外，所有六个菌株都能在所有品系的100%植株上诱发严重的萎蔫症状。通过使用一组能够区分所有三个FOL生理小种以及尖孢镰刀菌番茄根腐专化型菌株的特异性引物进行PCR检测，确认了FOL 3号生理小种的身份（1）。从在琼脂培养基上生长的纯真菌菌落中提取总DNA。仅在来自巴伊亚州的六个FOL 3菌株以及五个3号生理小种的参考菌株（先前从圣埃斯皮里图州和里约热内卢州的番茄中获得）中观察到典型的FOL 3号生理小种扩增子图谱（即引物uni、sp13和sp23呈阳性，引物sprl呈阴性），从而确认了它们的生理小种身份。FOL 3号生理小种近期在巴西迅速且广泛的地理扩张表明，该病原菌是通过受污染的种子或幼苗被引入到新的番茄种植区的。由于制定有效的化学和栽培防治策略较为复杂，FOL 3号生理小种在巴西不同地区引发的这些疫情可能会导致目前种植的易感杂交种被抗性杂交种所取代。参考文献：（1）Y. Hirano和T. Arie。《植物病理学报》72:273，2006；（2）A. Reis等人。《巴西植物病理学》30:426，2005；（3）A. Reis和L. S. Boiteux。《巴西园艺》25:451，2007。
