Abstract：
Pythium sensu lato (s.l.) is a pathogenic oomycete. The present study was conducted to isolate and identify Pythium s.l. species associated with the rhizosphere and roots of greenhouse-growing cucumbers showing damping-off symptoms in 10 Omani governorates (provinces). A total of 166 isolates were recovered from 276 rhizosphere soil and root samples and were identified based on the ribosomal DNA (rDNA) internal transcribed spacer (ITS) region and the cytochrome c oxidase subunit I (COX I) gene region. Pythium aphanidermatum, P. myriotylum, Globisporangium spinosum, Globisporangium sp.1 (isolates Kb003/PySyCu-1 and Kb004/PySyCu-2), and Globisporangium sp.2 (isolate Ib002R) were identified. Among these species, P. aphanidermatum was the most abundant species, represented by 143 isolates (86.1%), followed by G. spinosum with 18 isolates (10.8%), Globisporangium sp.1 and P. myriotylum each with 2 isolates (2.4%), and Globisporangium sp.2 with 1 isolate (0.6%). Pathogenicity tests were also conducted for 38 isolates, including P. aphanidermatum (25), P. myriotylum (2), Globisporangium sp.2 (1), G. spinosum (8), and Globisporangium sp.1 (2). Among the tested isolates, only Globisporangium sp.2 isolate was avirulent, and none of the seeds were rotted at the end of the treatment. However, the other species induced the symptoms of seed decay with the incidence ranged from 86.7 to 100%. Phylogenetic analyses were conducted based on 222 ITS and 53 COX I sequences, and confirmed morphological identification. In addition, the genetic diversity of 93 P. aphanidermatum isolates was assessed via the amplified fragment length polymorphism (AFLP) method. The analysis produced 93 genotypes and 449 polymorphic loci. Pythium aphanidermatum populations were found to have moderate levels of genetic diversity (H = 0.2) and a moderate Shannon information index (I = 0.3793). Analysis of molecular variance (FST = 0.1, P = 0.0) revealed a moderate level of genetic differentiation among P. aphanidermatum isolates between Oman governorates. The sensitivity of 15 P. aphanidermatum isolates was evaluated against hymexazol at different concentrations (10, 100, and 1000 ppm). The results revealed that P. aphanidermatum could grow well at concentrations of up to 100 ppm hymexazol. However, hymexazol at 1000 ppm retarded the growth of P. aphanidermatum. This study showed that P. aphanidermatum is the most prevalent species in greenhouses in Oman and exhibited a moderate level of genetic diversity. Most of the isolates exhibited differences in tolerance to hymexazol but showed no resistance.
摘要：
S.Lato腐霉（s.l.）是一种致病性卵菌。进行本研究是为了分离和鉴定与10个阿曼省（省）温室黄瓜的根际和根相关的Pythiums.l。从276个根际土壤和根样品中总共回收了166个分离株，并根据核糖体DNA（rDNA）内部转录间隔区（ITS）区域和细胞色素c氧化酶亚基I（COXI）基因区域进行了鉴定。Phanipermesticum,肉豆蔻，刺球孢菌，球孢菌sp.1（分离出Kb003/PySyCu-1和Kb004/PySyCu-2），并鉴定了球孢菌sp.2（分离株Ib002R）。在这些物种中,P.aphanipermasum是最丰富的物种，由143个分离株(86.1%)代表，其次是spinosum，有18个分离株(10.8%)，球孢菌sp1和肉豆蔻菌各2个分离株（2.4%），球孢菌sp2，分离株1株（0.6%）。还对38个分离株进行了致病性测试，包括隐线菌属(25)，肉芽胞杆菌（2），球孢菌sp.2（1），G.spinosum（8），和球孢菌sp.1（2）。在测试的分离物中，只有球形孢子菌sp2分离株是无毒的，在处理结束时没有一个种子腐烂。然而,其他物种引起种子腐烂症状，发生率为86.7％至100％。基于222个ITS和53个COXI序列进行了系统发育分析，并确认了形态学鉴定。此外,通过扩增片段长度多态性（AFLP）方法评估了93例失光假单胞菌的遗传多样性。分析产生了93个基因型和449个多态性位点。发现无皮腐霉种群具有中等水平的遗传多样性（H=0.2）和中等的Shannon信息指数（I=0.3793）。分子方差分析（FST=0.1，P=0.0）显示，阿曼各省之间的Phaniikermice分离株之间的遗传分化水平适中。在不同浓度（10、100和1000ppm）下，评估了15种Phanikermasefum分离株对hymexazol的敏感性。结果表明，在高达100ppm的hymexazol浓度下，Phanikermina可以很好地生长。然而,1000ppm的hymexazol延缓了P的生长。这项研究表明，Phanikermasum是阿曼温室中最普遍的物种，并表现出中等水平的遗传多样性。大多数分离株对hymexazol的耐受性存在差异，但没有耐药性。
