Gray leaf spot (GLS) disease, caused by the Stemphylium (Sm) fungus, affects a wide range of horticultural crops including tomato. In this study, the South Korean Sm isolate (PNU-SM01) was identified, and the applicability of Sm-resistance gene (Sm)-linked DNA markers in marker-assisted selection was validated. ITS/gpd sequencing and morphological observation identified the isolate as S. lycopersici. A GLS disease assay was conducted on 80 tomato varieties, including commercial F₁ hybrids and elite inbred lines. The reference line ‘Motelle’ was highly resistant (R, DSI = 4.0), whereas the ‘Moneymaker’ line was susceptible (S) and showed severe disease symptoms (DSI = 79.3). Among 30 commercial F₁ hybrids, five were scored as S by DSI; whereas the rest, including all 17 hybrids claimed as Sm-resistant by the supplier, were R or moderately resistant (MR). Among 48 inbred lines, four were scored as S and 44, including five Lycopersicon accessions reported as R, were R or MR. Three known Sm-linked DNA markers (CT55, D5, and Sm-InDel) were genotyped in all 80 cultivars; the highest match (92.5%) to the GLS disease assay was observed for Sm-InDel. We converted the recessive marker CT55 into a codominant marker (CT55-Co) and developed dCAPS (Sm-SNP) and KASP (Sm-KASP) markers from a previously identified Sm-linked SNP. Sm-SNP and Sm-KASP showed a similar level of phenotype to marker genotype association as Sm-InDel, whereas CT55-Co displayed a high level of mismatch. To screen for the source of Sm resistance, 138 tomato accessions were genotyped with Sm-InDel and Sm-SNP: 15 were homozygous for the resistance allele of both markers. In this study, resistance to the Korean isolate of S. lycopersici in commercial F₁ hybrids and breeding sources was characterized to reveal which DNA markers can be effectively applied for marker-assisted selection of Sm-resistance.

灰色叶斑病（GLS）病，引起的匍柄霉（SM）的真菌，影响很多园艺作物包括番茄的。在这项研究中，确定了韩国Sm分离株（PNU-SM01），并验证了Sm抗性基因（Sm）连锁的DNA标记在标记辅助选择中的适用性。ITS / gpd测序和形态学观察鉴定出该分离物为S. lycopersici。对80个番茄品种（包括商业F ₁杂种和优良自交系）进行了GLS疾病分析。参考系“ Motelle”具有高度抗性（R，DSI = 4.0），而“ Moneymaker”系易感（S）并显示出严重的疾病症状（DSI = 79.3）。在30个商业F中_1个杂种，5个被DSI评为S；而其余的，包括供应商声称具有Sm抗性的所有17个杂种，均为R或中度抗性（MR）。在48个自交系中，有4个被评为S，有44个，包括五个被报告为R的番茄属，分别为R或MR。在所有80个品种中对三种已知的Sm连接的DNA标记（CT55，D5和Sm-InDel）进行了基因分型。观察到Sm-InDel与GLS疾病分析的最高匹配率（92.5％）。我们将隐性标记物CT55转换为共性标记物（CT55-Co），并从先前鉴定的Sm中开发了dCAPS（Sm-SNP）和KASP（Sm-KASP）标记物连锁的SNP。Sm-SNP和Sm-KASP与Sm-InDel表现出相似的表型水平与标记基因型关联，而CT55-Co表现出高水平的错配。为了筛选Sm抗性的来源，用Sm-InDel和Sm-SNP对138个番茄种质进行了基因分型：两个标记的抗性等位基因中有15个纯合。在这项研究中，对商业F ₁杂种和育种来源中的韩国番茄链球菌的抗性进行了表征，揭示了哪些DNA标记可以有效地用于标记辅助选择的Sm抗性。