Genetic Diversity and Structure of Neotyphodium Species and Their Host Achnatherum sibiricum in a Natural Grass–Endophyte System
Genetic Diversity and Structure of Neotyphodium Species and Their Host Achnatherum sibiricum in a Natural Grass–Endophyte System
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DOI：
10.1007/s00248-010-9652-3
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发表时间：
2010-03
影响因子：
3.6
通讯作者：
Xin Zhang;A. Ren;H. Ci;Yu-bao Gao
中科院分区：
文献类型：
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作者：
Xin Zhang;A. Ren;H. Ci;Yu-bao Gao
西伯利亚芨芨草（禾本科）是一种多年生束草，原产于中国内蒙古草原。这种草通常被表绿内生菌感染，感染频率很高。之前，我们鉴定了两种主要的Neotyphodium spp.,N。西伯利亚和N.甘肃。在本研究中，分析了两种主要的Neotyphodium spp 的遗传多样性和结构。以及寄主草。我们从 5 个种群中获得了 103 株真菌分离株； 33个被鉴定为N。西伯利亚和 61 asN。甘肃。所有种群都拥有两种内生物种，但 N 的遗传变异要高得多。甘肃省N.西伯利亚。大多数真菌分离株是单倍体，其中 13% 在一个 SSR 基因座上是杂合的，表明这些分离株是杂合起源。真菌SSR位点的显着连锁不平衡表明，这两种真菌主要通过植物种子进行克隆生长繁殖，而遗传多样性的变化和两种内生物种中杂种的存在表明，尽管克隆繁殖很普遍，但偶尔也可能发生重组。通过比较种群之间的遗传分化，我们发现内生菌种群的分化程度比宿主种群高约 4-7 倍，这意味着内生菌的基因流比宿主更受限制。我们提出A的内生菌感染。在某些条件下，西伯利亚可能赋予宿主一些选择优势，这有助于维持宿主群体中高内生菌感染频率，即使它们的基因流彼此不匹配。此外，我们建议，如果研究的目的是了解内生菌或寄主基因型对其共生关系的影响，则应确认内生菌和寄主基因型相同，而不是仅仅考虑植物是否被内生菌感染，因为来自同一寄主物种的内生菌可能表现出高水平的遗传多样性，这很可能影响其共生关系的结果。
Achnatherum sibiricum(Poaceae) is a perennial bunchgrass native to the Inner Mongolia Steppe of China. This grass is commonly infected by epichloë endophytes with high-infection frequencies. Previously, we identified two predominantNeotyphodiumspp.,N. sibiricumandN. gansuense. In the present study, genetic diversity and structure were analyzed for the two predominantNeotyphodiumspp. as well as the host grass. We obtained 103 fungal isolates from five populations; 33 were identified asN. sibiricumand 61 asN. gansuense. All populations hosted both endophytic species, but genetic variation was much higher forN. gansuensethan forN. sibiricum. The majority of fungal isolates were haploid, and 13% of them were heterozygous at one SSR locus, suggesting hybrid origins of those isolates. Significant linkage disequilibrium of fungal SSR loci suggested that both fungal species primarily propagate by clonal growth through plant seeds, whereas variation in genetic diversity and the presence of hybrids in both endophytic species revealed that although clonal propagation was prevalent, occasional recombination might also occur. By comparing genetic differentiation among populations, we found around 4–7-fold greater differentiation of endophyte populations than host populations, implying more restricted gene flow of endophytes than hosts. We proposed that endophyte infection ofA. sibiricummight confer the host some selective advantages under certain conditions, which could help to maintain high-endophyte-infection frequencies in host populations, even when their gene flows do not match each other. Furthermore, we suggested that the same genotype of endophyte as well as host should be confirmed if the objective of the study is to know the influence of endophyte or host genotype on their symbiotic relationship, instead of just considering whether the plant is infected by an endophyte or not, since endophytes from the same host species could exhibit high levels of genetic diversity, which is likely to influence the outcome of their symbiotic relationship.