猕猴桃(猕猴桃)是韩国经济上重要的水果,种植面积为1,300公顷,年产量约为25,000吨(Kim和Koh,2018;Kim和Choi,2023年)。在2020年6月下旬,在A.chinensisvar上观察到果实结痂症状。在顺川的一个果园里,韩国。在20岁的树木中,结痂症状的发生率超过75%,主要是肤浅的,但使水果的适销对路.在疾病的初始阶段,小,浅棕色,圆形,形成椭圆形斑点。随着表面斑点的扩大,在后期,它们变成了1至7厘米长的龟裂,边缘浅。为了分离病原体,从两个有症状的组织切片上切下两个病灶,来自七棵树上的七种水果。用70%乙醇表面灭菌1分钟,并用灭菌蒸馏水(SDW)洗涤3次。将灭菌的片置于马铃薯葡萄糖琼脂(PDA)上并在黑暗中在25°C下孵育一周。在PDA上进行继代培养后,单孢子分离产生14个分离株:SYP-410至423)。7d后,所有14个菌落在PDA上出现灰绿色和棉色。分生孢子为浅棕色,椭圆体到椭圆体,装饰墙壁,1至6个横向和0至3个垂直隔片,长度×宽度为21.5至53.4×7.3至19.2μm(平均33.0×12.0μm,n=100)。它们的形态特征与链格孢菌属一致。(范德华等人。2011;Woudenberg等人。2015).我们从形态相似的培养物中随机选择了三个分离株,并将其命名为SYP-412至414,以进行进一步研究。ITS(GenBank登录号:OR901850至52),gapdh(OR924309至11),tef1(OR924312到14),rpb2(OR924315到17),Alta1(OR924318到20),endoPG(OR924321至23),从SYP-412到414的OPA10-2(OR924324到26)序列具有100%(515bp/515bp),100%(578/578),100%(240/240),100%(724/724),95.55%(451/472),99.33%(445/448),和100%(634/634)的同一性与菌株A.alternataCBS918.96(AF347032,AY278809,KC584693,KC584435,AY563302,KP124026和KP124633),分别。最大似然系统发育分析的结果,基于七个串联的基因序列,将代表性分离株与A.alternata放在一个分支中。在20岁的树上使用12个表面灭菌的两个月大的猕猴桃测试了SYP-412的致病性。在PDA培养基中培养7d后,用5mL分生孢子悬浮液(1×106分生孢子/ml)对6个猕猴桃进行喷雾接种,有或没有受伤。用SDW接种另外六个对照果实,并没有受伤。将接种的猕猴桃装入塑料袋中以保持高湿度一天。接种后六周,在受伤和未受伤的水果中均观察到赤霉病症状,但不是在控制中。对总共三个单独的树进行了两次致病性测试。为了满足科赫的假设,从所有有症状的组织中重新分离出交替A,并通过分析ITS和rpb2基因进行确认。尽管先前已在A.chinensisvar的猕猴桃中报道了由A.tenuissima(现为A.alternata)引起的sc病。rufopulpa在中国(Woudenberg等人2015年;马等人。,2019),这是韩国猕猴桃发生的第一份报告,将有助于未来的检测和控制。
Kiwi (Actinidia chinesis) is an economically important fruit in Korea, with 1,300 ha cultivated and a production of approximately 25,000 tons per year (Kim and Koh, 2018; Kim and Choi, 2023). In late June 2020, fruit scab symptoms were observed on A. chinensis var. rufopulpa in an orchard in Suncheon, Korea. The incidence of scab symptoms among 20-year-old trees was over 75%, primarily superficial, but rendered the fruit less marketable. In the initial stages of the disease, small, light-brown, circular, and oval spots were formed. As the superficial spots expanded, they became cracked scabs measuring 1 to 7 cm with light edges at the later stages. To isolate the causal pathogen, two lesions were cut from two sections of symptomatic tissue, from each of seven fruits from seven trees. Lesions were surface-sterilized with 70% ethanol for 1 min and washed three times with sterilized distilled water (SDW). The sterilized pieces were placed on potato dextrose agar (PDA) and incubated in the dark at 25°C for one week. After subculturing on PDA, single-spore isolation produced 14 isolates: SYP-410 to 423). All 14 colonies appeared greyish-green and cottony on PDA after 7 d. Conidia were pale brown, ellipsoid to obclavate, with ornamented walls, 1 to 6 transverse and 0 to 3 vertical septa, and length × width of 21.5 to 53.4 × 7.3 to 19.2 μm (avg. 33.0 × 12.0 μm, n = 100). Their morphological characteristics were consistent with Alternaria spp. (van der Waals et al. 2011; Woudenberg et al. 2015). We randomly selected three isolates from the morphologically similar cultures and named them SYP-412 to 414 for further investigation. The ITS (GenBank accession nos.: OR901850 to 52), gapdh (OR924309 to 11), tef1 (OR924312 to 14), rpb2 (OR924315 to 17), Alt a1 (OR924318 to 20), endoPG (OR924321 to 23), and OPA10-2 (OR924324 to 26) sequences from SYP-412 to 414 had a 100% (515 bp/515 bp), 100% (578/578), 100% (240/240), 100% (724/724), 95.55% (451/472), 99.33% (445/448), and 100% (634/634) identity with that of type strain A. alternata CBS 918.96 (AF347032, AY278809, KC584693, KC584435, AY563302, KP124026, and KP124633), respectively. Results from the maximum likelihood phylogenetic analysis, based on the seven concatenated gene sequences, placed the representative isolates in a clade with A. alternata. Pathogenicity of SYP-412 was tested using 12 surface-sterilized two-month-old kiwifruits on a 20-year-old trees. Six kiwifruits were spray-inoculated with 5 mL of a conidial suspension (1 × 106 conidia/ml) generated after culturing in PDA medium for 7 d, with or without wounding. Another six control fruits were inoculated with SDW with and without wounding. The inoculated kiwifruits were enclosed in plastic bags to maintain high humidity for one day. Scab symptoms were observed in both wounded and unwounded fruits six weeks after inoculation, but not in the control. The pathogenicity test was performed on a total of three separate trees twice. To satisfy Koch\'s postulates, A. alternata was re-isolated from all the symptomatic tissues and confirmed by analyzing the ITS and rpb2 genes. Although scab disease caused by A. tenuissima (now A. alternata) has been previously reported in kiwifruit of A. chinensis var. rufopulpa in China (Woudenberg et al. 2015; Ma et al., 2019), this is the first report of its occurrence on kiwifruit in Korea and will help in future detection and control.