Southwood Michael J, Viljoen Altus, Mostert Lizel, Rose Lindy J, McLeod Adéle
Department of Plant Pathology, Stellenbosch University, Private Bag X1, Matieland, 7600, South Africa.
Plant Dis. 2012 Sep;96(9):1250-1261. doi: 10.1094/PDIS-10-11-0820-RE.
Fusarium oxysporum f. sp. cepae causes Fusarium basal rot of onion, a disease of worldwide importance. Limited information is available on the phylogenetic diversity, vegetative compatibility groups (VCGs), mating type idiomorphs, and virulence of F. oxysporum isolates associated with onion. Therefore, these characteristics were investigated in 19 F. oxysporum f. sp. cepae isolates from Colorado, 27 F. oxysporum f. sp. cepae and 33 F. oxysporum isolates nonpathogenic to onion from South Africa. Six F. oxysporum f. sp. cepae VCGs (0421 to 0426) were identified, of which three were new. The dominant VCGs in Colorado and South Africa were VCG 0421 (47% of isolates) and VCG 0425 (74%), respectively. VCG 0423 was the only VCG that was shared between the two regions. Molecular phylogenies (intergenic spacer region of the rDNA, elongation factor 1α, and mitochondrial small-subunit) confirmed the polyphyletic nature of F. oxysporum f. sp. cepae and showed that some F. oxysporum f. sp. cepae and nonpathogenic F. oxysporum isolates were genetically related. Most F. oxysporum f. sp. cepae isolates clustered into two distinct, well-supported clades. The largest clade only contained highly virulent isolates, including the two main VCGs (0421 and 0425), whereas the basal clade mostly contained moderately virulent isolates. These groupings along with the VCG data provide an important basis for selection of isolates for use in breeding programs, and for the development of molecular makers to identify VCGs. Mating type genotyping revealed the distribution of both mating type (MAT1-1 and MAT1-2) idiomorphs across phylogenetic clades, and the fact that several isolates contained both idiomorphs.
尖孢镰刀菌洋葱专化型（Fusarium oxysporum f. sp. cepae）引发洋葱镰刀菌基腐病，这是一种具有全球重要性的病害。关于与洋葱相关的尖孢镰刀菌分离株的系统发育多样性、营养体亲和群（VCGs）、交配型特异形态以及毒力的信息有限。因此，对来自科罗拉多州的19株尖孢镰刀菌洋葱专化型分离株、来自南非的27株尖孢镰刀菌洋葱专化型分离株以及33株对洋葱无致病性的尖孢镰刀菌分离株的这些特征进行了研究。鉴定出了6个尖孢镰刀菌洋葱专化型VCGs（0421至0426），其中3个是新的。科罗拉多州和南非的优势VCGs分别是VCG 0421（占分离株的47%）和VCG 0425（占74%）。VCG 0423是两个地区共有的唯一VCG。分子系统发育分析（rDNA的基因间隔区、延伸因子1α和线粒体小亚基）证实了尖孢镰刀菌洋葱专化型的多系性质，并表明一些尖孢镰刀菌洋葱专化型和无致病性的尖孢镰刀菌分离株在遗传上相关。大多数尖孢镰刀菌洋葱专化型分离株聚为两个不同的、得到有力支持的分支。最大的分支仅包含高毒力分离株，包括两个主要的VCGs（0421和0425），而基部分支大多包含中等毒力分离株。这些分组以及VCG数据为选择用于育种计划的分离株以及开发用于鉴定VCGs的分子标记提供了重要依据。交配型基因分型揭示了两种交配型（MAT1-1和MATI-2）特异形态在系统发育分支中的分布情况，以及几个分离株同时含有两种特异形态的事实。
