Texas AgriLife Research and Extension Center, Department of Horticultural Sciences, Texas A&M University, Dallas, TX 75252, USA.
Mycopathologia. 2012 Dec;174(5-6):371-82. doi: 10.1007/s11046-012-9573-4. Epub 2012 Aug 23.
Simple sequence repeat (SSR) markers were developed from Aspergillus flavus expressed sequence tag (EST) database to conduct an analysis of genetic relationships of Aspergillus isolates from numerous host species and geographical regions, but primarily from the United States. Twenty-nine primers were designed from 362 tri-nucleotide EST-SSR sequences. Eighteen polymorphic loci were used to genotype 96 Aspergillus species isolates. The number of alleles detected per locus ranged from 2 to 24 with a mean of 8.2 alleles. Haploid diversity ranged from 0.28 to 0.91. Genetic distance matrix was used to perform principal coordinates analysis (PCA) and to generate dendrograms using unweighted pair group method with arithmetic mean (UPGMA). Two principal coordinates explained more than 75 % of the total variation among the isolates. One clade was identified for A. flavus isolates (n = 87) with the other Aspergillus species (n = 7) using PCA, but five distinct clusters were present when the others taxa were excluded from the analysis. Six groups were noted when the EST-SSR data were compared using UPGMA. However, the latter PCA or UPGMA comparison resulted in no direct associations with host species, geographical region or aflatoxin production. Furthermore, there was no direct correlation to visible morphological features such as sclerotial types. The isolates from Mississippi Delta region, which contained the largest percentage of isolates, did not show any unusual clustering except for isolates K32, K55, and 199. Further studies of these three isolates are warranted to evaluate their pathogenicity, aflatoxin production potential, additional gene sequences (e.g., RPB2), and morphological comparisons.
简单序列重复（SSR）标记是从黄曲霉表达序列标签（EST）数据库中开发出来的，用于分析来自众多宿主物种和地理区域的曲霉分离物的遗传关系，但主要来自美国。从 362 个三核苷酸 EST-SSR 序列中设计了 29 个引物。使用 18 个多态性位点对 96 个曲霉种分离物进行基因分型。每个位点检测到的等位基因数从 2 到 24 不等，平均值为 8.2 个等位基因。单倍型多样性范围从 0.28 到 0.91。遗传距离矩阵用于执行主坐标分析（PCA），并使用不带权对组平均法（UPGMA）生成聚类树。两个主坐标解释了分离物之间总变异的 75%以上。使用 PCA 对黄曲霉分离物（n=87）进行分析时，鉴定出一个分支，而其他曲霉种（n=7）则形成一个分支，但在不包括其他分类群进行分析时，存在五个不同的聚类。当使用 UPGMA 比较 EST-SSR 数据时，注意到六个组。然而，当使用 PCA 或 UPGMA 进行比较时，没有与宿主物种、地理区域或黄曲霉毒素产生直接关联。此外，与肉眼可见的形态特征（如菌核类型）也没有直接的相关性。密西西比三角洲地区的分离物含量最大，除了 K32、K55 和 199 三个分离物外，没有显示出任何不寻常的聚类。需要进一步研究这三个分离物，以评估它们的致病性、黄曲霉毒素产生潜力、其他基因序列（如 RPB2）和形态比较。
