Kochánková Jana, Mandák Bohumil
Faculty of Environmental Sciences, Czech University of Life Sciences, Kamýcká 129, CZ-165 21 Praha, Czech Republic.
Ann Bot. 2009 Jun;103(8):1303-13. doi: 10.1093/aob/mcp073. Epub 2009 Apr 1.
The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic population genetic parameters correlate with seed germinability under various experimental conditions was tested.
Population genetic diversity was ascertained in eight populations of A. tatarica by assessing patterns of variation at nine allozyme loci. Germinability of both seed types from all sampled populations was determined by a common laboratory experiment under different salinity levels. Basic population genetic parameters, i.e. percentage of polymorphic loci, average number of alleles per locus and observed heterozygosity were correlated with observed population germination characteristics.
Atriplex tatarica possesses a remarkable heterocarpy, i.e. one type of seed is non-dormant and the other shows different dormancy levels in relation to experimental conditions. Significant negative correlations have been detected between germination of both seed types and the coefficient of inbreeding, and a significant negative correlation between germination of dormant seeds and other population genetic parameters, i.e. percentage of polymorphic loci and average number of alleles per polymorphic locus. Moreover, populations from the region characterized by a shorter growing season manifested higher germinability, i.e. had lower dormancy, than those from the lower-latitude one.
In general, germination of non-dormant seeds is probably not under strong genetic control. Hence, they germinate as soon as conditions are favourable, thus ensuring survival in the short term, but populations risk local extinction if conditions become adverse (i.e. a high-risk strategy). In contrast, germination of the dormant type of seeds is under stronger genetic control and is significantly correlated with basic population genetic parameters. These seeds ensure long-term reproduction and survival in the field by protracted germination, albeit in low quantities (i.e. A. tatarica also adopts a low-risk strategy).
异果滨藜会产生两种类型的种子。在本研究中，测试了基本种群遗传参数与不同实验条件下种子发芽能力之间的相关性。
通过评估9个等位酶位点的变异模式，确定了8个异果滨藜种群的种群遗传多样性。在不同盐度水平下，通过常规实验室实验测定了所有采样种群中两种种子类型的发芽能力。将基本种群遗传参数，即多态位点百分比、每个位点的平均等位基因数和观察到的杂合度，与观察到的种群发芽特征进行关联分析。
异果滨藜具有显著的异果性，即一种种子是非休眠的，另一种种子在不同实验条件下表现出不同的休眠水平。已检测到两种种子类型的发芽率与近亲繁殖系数之间存在显著负相关，休眠种子的发芽率与其他种群遗传参数，即多态位点百分比和每个多态位点的平均等位基因数之间存在显著负相关。此外，生长季节较短地区的种群比低纬度地区的种群表现出更高的发芽能力，即休眠程度更低。
一般来说，非休眠种子的发芽可能不受强遗传控制。因此，一旦条件适宜它们就会发芽，从而确保短期内的生存，但如果条件变得不利（即高风险策略），种群就有局部灭绝的风险。相比之下，休眠型种子的发芽受更强的遗传控制，并且与基本种群遗传参数显著相关。这些种子通过长期发芽确保了在田间的长期繁殖和生存，尽管数量较少（即异果滨藜也采用低风险策略）。
