Population structure and mating system of Ascochyta rabiei in Tunisia: evidence for the recent introduction of mating type 2
Population structure and mating system of Ascochyta rabiei in Tunisia: evidence for the recent introduction of mating type 2
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突尼斯Ascochyta rabiei的种群结构和交配系统：最近引入2型交配的证据
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
P. Dyer
中科院分区：
文献类型：
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作者：
A. Rhaiem;M. Chérif;T. Peever;P. Dyer
利用简单序列重复标记(SSR)和交配型标记(MAT)对突尼斯鹰嘴豆主产区的5个种群进行了群体结构分析。与交配类型1菌株(MAT1-1)相比，交配类型2菌株(MAT1-2)的遗传多样性和基因多样性降低。这一结果，再加上突尼斯以前观察到的MAT1-2总体频率较低和地理分布受限，以及最近(2001年)对性阶段的观察，支持最近引入MAT1-2的假设。尽管在Nabeul、Kef和Jendouba存在两种交配类型，但通过多位点配对不平衡测试，随机交配的假说在这些位置被拒绝。群体间存在极显著的遗传分化(！=0·32，G ST=0·28，P<；0·001)，遗传距离和基于等位基因频率的聚类分析表明，Nabeul和Kef的群体与Beja、Bizerte和Jendouba的群体不同。超过70%的总基因多样性(HT=0·55)可归因于种群内的变异，而种群间的这一比例为28%。这一结果，再加上每个种群中出现的私人等位基因，表明目前种群之间的基因流动是有限的，即使是那些地理距离较短的种群。通过基于贝叶斯模型的多位点基因类型(MLGs)群体结构分析，证实了两个主要遗传簇的存在，而不考虑样本的地理来源。在这两个集群中都存在MAT1-2分离株，这表明至少有两次MAT1-2独立引入突尼斯，这可能是进口和种植受感染的鹰嘴豆种子的结果。
The population structure of Ascochyta rabiei (teleomorph: Didymella rabiei ) in Tunisia was estimated among five populations sampled from the main chickpea growing regions using simple sequence repeat markers (SSR) and a mating type ( MAT ) marker. Mating type 2 isolates ( MAT1-2 ) had reduced genetic and genotypic diversity relative to mating type 1 isolates ( MAT1-1 ). This result, coupled with previous observations of lower overall frequency and restricted geographical distribution of MAT1-2 in Tunisia, and recent (2001) observation of the sexual stage, support the hypothesis of a recent introduction of MAT1-2 . Despite the presence of both mating types in Nabeul, Kef and Jendouba, the hypothesis of random mating was rejected in these locations with multilocus gametic disequilibrium tests. Highly significant genetic differentiation ( ! = 0·32, G ST = 0·28, P < 0·001) was detected among populations and genetic distance and cluster analyses based on pooled allele frequencies revealed that populations from Nabeul and Kef were distinct from those in Beja, Bizerte and Jendouba. More than 70% of total gene diversity ( H T = 0·55) detected was attributable to variation within populations compared to 28% among populations. This result, coupled with the occurrence of private alleles in each population, suggests that gene flow is currently limited among populations, even those separated by short geographic distances. The presence of two main genetic clusters was confirmed using Bayesian model-based population structure analyses of multilocus genotypes (MLGs) without regard to geographic origin of samples. The presence of MAT1-2 isolates in both clusters suggests at least two independent introductions of MAT1-2 into Tunisia that are likely to be the result of importation and planting of infected chickpea seeds.