西番莲属,俗称百香果,起源于南美洲,是一种重要的经济园艺作物,在热带和亚热带地区分布广泛。黄色百香果(西番莲edulis.flaticarpa)和紫色百香果(西番莲edulis.edulis)是种植最多的两个物种(Santos-Jiménez等人。,2022),主要在中国南方种植。平均年产量达到60万吨,其中黄色水果占70%以上(Zhou等人。,2022年)。在2022年至2023年,一种疾病导致百香果种植园严重腐烂。紫色百香果的发病率一般为10%,黄色百香果中的发病率高达60%。9\'。花腐病主要发生在雨季,尤其是在长时间下雨的时候。受感染的花朵有黑色斑点,被水浸在花蕾的内部。这些补丁覆盖了整个花蕾,蓬松的菌丝体和孢子囊发育,这导致花蕾腐烂和容易脱落。五花有症状的花,广东(北纬23°23,115°18\'E)和8朵来自上思的有症状的花,广西(北纬21°15,107°98\'E)\'秦密编号在2022年和2023年的开花期收集了9\'。用70%乙醇对患病的花进行表面灭菌2至3分钟,用无菌蒸馏水冲洗3次,置于25℃黑暗环境下的PDA培养基上。从五华和上思的感染样品中分离出形态相似的真菌4株和6株,分别。两个分离株,五华的PRFJ01和上思的PRGX02,随机选择进行进一步研究。3日龄的纯化真菌菌落伴随弥漫性棉质菌丝体,后来变成了灰色。菌丝体呈透明和无菌。直立孢子长0.56(0.22~1.10)mm,宽6.1(3.18~10.87)μm(n=100),浅棕色,在其基部有根状茎和茎。孢子囊直径为48.0(23.45~92.85)μm(n=100),呈深色,近球形,深卵形孢子,3.56(2.34~6.39)μm×2.82(1.73~4.70)μm(n=100)。真菌的形态与Stolonifer根霉(Ehrenb。)Vuill(Haque等人。2023年)。使用具有NL1和LR3引物的28S大核糖体亚基(LSU)的基因组区域对这两个分离株进行了分子鉴定(Cruz-Lachica等。,2018)。系统发育树显示PRFJ01(OR801560.1)和PRGX02(OR801561.1)的序列与r.stolonifer(MK705761.1和KC412868.1)100%和99%相同,分别。对5个月大嫁接的\'QinmiNo.的健康花朵和叶子进行了致病性测试。9\'植物。将直径为5mm的菌丝体塞置于花和叶上。对每个分离株进行了三株植物,测试重复两次。接种的植物用塑料袋润湿。用无菌PDA塞接种的健康花和叶用作对照。2天后在接种的植物上观察到典型的症状。接种4天后,深灰色菌丝体和孢子囊覆盖了整个花。花蕾腐烂,花茎裂开。叶片上的病变扩张伴随着许多气生菌丝体。然而,对照组没有症状.从接种的组织中重新分离出Stolonifer。以前,只有在巴西才有记录(Ploetz,2003).据我们所知,这是在中国首次报道了在百香果上引起花腐病的R.stolonifer。
The genus Passiflora, commonly known as passion fruit, originated in South America, is an economically important horticulture crop and widely distributed in the tropics and subtropics. Yellow passion fruit (Passiflora edulis f. flavicarpa) and purple passion fruit (Passiflora edulis f. edulis) are the two most planted species (Santos-Jiménez et al., 2022), which have been largely cultivated in southern China. The average annual production reaches 600,000 tons, of which yellow fruit accounts for more than 70% (Zhou et al., 2022). In 2022 to 2023, a disease caused flower rot severely in passion fruit plantations. The incidence rate was generally 10% in purple passion fruit, with an incidence up to 60% in yellow passion fruit \'Qinmi No. 9\'. Flower rot occurs mainly in the rainy season, especially during periods of prolonged rain. Infected flowers had black patches that were water-soaked on the interior of the flower bud. The patches covered the entire flower bud, and fluffy mycelium and sporangia developed, which caused the flower bud rotten and abscised easily. Five symptomatic flowers from Wuhua, Guangdong (23°23\'N, 115°18\'E) and 8 symptomatic flowers from Shangsi, Guangxi (21°15\'N, 107°98\'E) of \'Qinmi No. 9\' were collected during flowering period in 2022 and 2023. Diseased flower pieces were surface-sterilized with 70% ethanol for 2 to 3 min, rinsed with sterile distilled water 3 times, and placed on PDA medium at 25℃ in darkness. Four and 6 fungal isolates with similar morphology were isolated from the infected samples of Wuhua and Shangsi, respectively. Two isolates, PRFJ01 from Wuhua and PRGX02 from Shangsi, were randomly selected for further study. Purified fungal colonies at the age of 3 days accompany with diffuse cottony mycelia, turned white to gray later. The mycelia were hyaline and aseptate. Sporangiophores with 0.56 (0.22~1.10) mm in length and 6.1 (3.18~10.87) μm in width (n=100) were erect, light brown, and had rhizoids and stolons at their bases. Sporangia with 48.0 (23.45~92.85) μm in diameter (n=100) were dark-colored, near spherical and having dark ovoid sporangiospores with 3.56 (2.34~6.39) μm × 2.82 (1.73~4.70) μm (n=100). The morphology of the fungus were identical to Rhizopus stolonifer (Ehrenb.) Vuill (Haque et al. 2023). The two isolates were molecularly identified using genomic regions of 28S large ribosomal subunit (LSU) with NL1 and LR3 primers (Cruz-Lachica et al., 2018). The phylogenetic trees revealed the sequences of PRFJ01 (OR801560.1) and PRGX02 (OR801561.1) were 100% and 99% identical to R. stolonifer (MK705761.1 and KC412868.1), respectively. Pathogenicity tests were conducted on healthy flowers and leaves of 5-month-old grafted \'Qinmi No. 9\' plants. Mycelial plugs with 5-mm diameter were placed on the flowers and leaves. Three plants were performed for each of the isolates, and the test was repeated twice. The inoculated plants were moisturized with plastic bags. Healthy flowers and leaves inoculated with sterile PDA plugs were used as control. Typical symptoms were observed on inoculated plants after 2 days. The dark grey mycelia and sporangia covered the entire flower after 4 days inoculation. The flower bud became putrid and the flower stalk split off. Lesions on leaves expanded accompany with numerous aerial mycelium. However, the controls were symptomless. R. stolonifer was reisolated from inoculated tissues. Previously, flower rot on passion fruit caused by R. stolonifer has only been recorded in Brazil (Ploetz, 2003). To our knowledge, this is the first report of R. stolonifer causing flower rot on passion fruit in China.