Fusarium oxysporum f. sp. lycopersici (FOL) races 1 and 2 were, up to recent years, the only pathogenic Fusaria associated with tomatoes (Solanum lycopersicum L.) in Brazil. However, recent outbreaks of F. oxysporum isolates with the ability to breakdown the I–2-mediated resistance prompted us to conduct nationwide surveys of the pathogens associated with vascular wilt of tomatoes. During these surveys, eight atypical F. oxysporum isolates (collected across five tomato–producing Brazilian states) displayed a peculiar ability of infecting accessions carrying the I–3 and I–7 genes (controlling resistance to FOL race 3 isolates). These observations suggested the involvement of either a new FOL race or of F. oxysporum f. sp. radicis-lycopersici (FORL) isolates. Koch’s postulates were fulfilled for these eight atypical isolates via root dipping inoculation (106 conidia mL− 1) of seedlings from two tomato cultivars ‘Ponderosa’ and ‘Dominador’. All eight isolates induced crown-rot symptoms only in ‘Ponderosa’, but not in ‘Dominador’ (which is resistant to FORL). To confirm the FORL identity, PCR assays were done using a set of race-specific and forma specialis-specific primers. A single amplicon of ≈ 947 bp was observed with the primer pair Sprl only with DNA template obtained from standard FORL isolates and from the eight atypical isolates, confirming the first detection of this forma specialis in Brazil. The geographical distribution of FORL isolates across major tomato–producing areas may require the incorporation of resistant factors into adapted cultivars.

中文翻译：

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Fusarium oxysporum f. 首次检测 sp. 巴西主要番茄产区的 radicis-lycopersici

尖孢镰刀菌 f. sp. lycopersici (FOL) 种族 1 和 2 是近年来巴西唯一与番茄 (Solanum lycopersicum L.) 相关的致病镰刀菌。然而，最近爆发的尖孢镰刀菌分离株具有破坏 I-2 介导的抗性的能力，促使我们对与番茄血管枯萎病相关的病原体进行全国性调查。在这些调查中，八种非典型尖孢镰刀菌分离株（在巴西五个产番茄的州收集）表现出感染携带 I-3 和 I-7 基因的种质（控制对 FOL 种族 3 分离株的抗性）的特殊能力。这些观察结果表明新的 FOL 种族或 F. oxysporum f. 的参与。sp. radicis-lycopersici (FORL) 分离株。通过对来自两个番茄栽培品种“Ponderosa”和“Dominador”的幼苗进行浸根接种（106 分生孢子 mL-1），这 8 个非典型分离株的 Koch 假设得到满足。所有八种分离株仅在“黄松”中引起冠腐症状，而在“多米纳多”（对 FORL 具有抗性）中没有。为了确认 FORL 身份，使用一组种族特异性和形式特异性引物进行 PCR 测定。仅使用从标准 FORL 分离株和 8 个非典型分离株获得的 DNA 模板的引物对 Sprl 观察到 ≈ 947 bp 的单个扩增子，证实了在巴西首次检测到这种特殊形式。FORL 分离株在主要番茄产区的地理分布可能需要将抗性因素纳入适应的栽培品种中。