Since the summer of 2020, severe decline and gummosis were observed on 20- to 30-year-old grapefruit trees cv. Star Ruby in Antalya province in the Western Mediterranean region of Türkiye. Grapefruit trees were examined in affected commercial orchards in Aksu, Manavgat, Muratpaşa and Serik counties, located near the coast of the Mediterranean Sea. Symptomatic trees exhibited leaf discoloration, defoliation and severe dieback, as well as dark, water-soaked lesions with gum exudates, characteristic of Phytophthora infections, formed on the bark of the main stem and major limbs. No Phytophthora species could be isolated from these bark tissues, while two were obtained from soil samples taken from around symptomatic trees. Based on morphological characteristics, isolates were identified as P. citrophthora and P. nicotianae. Identifications were confirmed by sequencing of the internal transcribed spacer (ITS) and the cytochrome oxidase I (cox1) gene regions. Pathogenicity tests, carried out by inoculations of the main stems and branches of grapefruit seedlings cv. Star Ruby indicated that both species were pathogenic. All P. citrophthora and P. nicotianae isolates obtained in this work were sensitive to mefenoxam. EC₅₀ values of P. citrophthora isolates were between 0.284 and 0.285 μg mL⁻¹, whereas those of P. nicotianae were between 0.288 and 0.291 μg mL⁻¹. Phytophthora citrophthora was previously known to cause disease on citrus in Türkiye, but this is the first report of P. nicotianae causing citrus gummosis in the country. Because P. nicotianae is more widespread than P. citrophthora, it should be considered a threat to citrus cultivation in this region of Türkiye.

中文翻译：

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柑橘疫霉和烟草疫霉导致土耳其南部葡萄柚（Citrus x paradisi Macfad.）严重衰退和流胶

自2020年夏季以来，20至30年树龄的葡萄柚树出现严重衰退和流胶现象。土耳其西地中海地区安塔利亚省的星红宝石。对位于地中海沿岸的阿克苏、马纳夫加特、穆拉特帕夏和塞里克县受影响的商业果园的葡萄柚树进行了检查。有症状的树木表现出叶子变色、落叶和严重枯萎，以及在主茎和主要枝的树皮上形成带有树胶渗出物的黑色水浸病斑，这是疫霉感染的特征。从这些树皮组织中无法分离出疫霉属物种，而从有症状的树木周围的土壤样本中分离出两种疫霉属物种。根据形态特征，分离菌株被鉴定为柠檬假单胞菌和烟草假单胞菌。通过对内部转录间隔区 (ITS) 和细胞色素氧化酶 I ( cox 1) 基因区域进行测序来确认鉴定。致病性试验，通过接种葡萄柚幼苗的主茎和枝条进行。星红宝石表明这两个物种都具有致病性。本研究中获得的所有柑橘疫霉和烟草疫霉分离株均对精甲霜灵敏感。柠檬假单胞菌分离株的EC ₅₀值在0.284和0.285 μg mL ^-1之间，而烟草假单胞菌的EC 50 值在0.288和0.291 μg mL ^-1之间。此前已知柑橘疫霉会在土耳其的柑橘上引起疾病，但这是该国首次报道烟草疫霉引起柑橘流胶病。由于烟草假单胞菌比柑橘假单胞菌分布更广，因此应将其视为对土耳其该地区柑橘种植的威胁。