Abstract Pyramiding of male-sterile genes in Cryptomeria japonica is currently being carried out in Niigata prefecture, Japan. This is the first attempt to apply pyramid breeding to forest trees. As the breeding materials for male sterility are limited, special attention must be given to increased genetic relatedness in the process of pyramid breeding to avoid the effects of inbreeding depression as much as possible. In this study, we estimated genetic relatedness based on 246 genome-wide SNP markers for male-sterile individuals in Niigata Prefecture (n = 6) and individuals doubly heterozygous for two male-sterile genes (hereafter referred to as “double-hetero”) produced by marker- assisted selection (n = 124). The pairwise relatedness estimates between male-sterile individuals selected from the same area in Niigata Prefecture were low (−0.01 ± 0.08, mean ± standard deviation), suggesting that there will be almost no negative effects even if the F1 of these male-sterile individuals is used for artificial crossing. On the other hand, the pairwise relatedness between double-hetero individuals in this study was higher than the theoretical relatedness values, as individuals with the slightly higher relatedness were used as parents in artificial crossings. However, there was a large variance in pairwise relatedness for double-hetero individuals. This result suggested that it may be possible to avoid the adverse effects of inbreeding depression by using a pair of double-heteros with lower relatedness for artificial crossing, when we produce a double-homo using the limited breeding materials of male- sterile individuals. It will also be important to continue additional selection of new breeding material for male sterility.

中文翻译：

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柳杉雄性不育树育种材料的遗传评价

摘要 日本新泻县目前正在对粳稻雄性不育基因进行金字塔分析。这是首次尝试将金字塔育种应用于林木。由于雄性不育育种材料有限，在金字塔育种过程中必须特别注意增加遗传相关性，尽可能避免近亲繁殖抑制的影响。在这项研究中，我们根据新泻县雄性不育个体（n = 6）和两个雄性不育基因双杂合个体（以下简称“双杂合”）的 246 个全基因组 SNP 标记估计了遗传相关性。由标记辅助选择产生（n = 124）。从新泻县同一地区选出的雄性不育个体之间的成对相关性估计值很低（-0.01 ± 0. 08，均值±标准差），表明即使将这些雄性不育个体的F1用于人工杂交，也几乎不会产生负面影响。另一方面，本研究中双异种个体之间的成对相关性高于理论相关性值，因为亲缘性稍高的个体在人工杂交中被用作父母。然而，双异种个体的成对相关性存在很大差异。该结果表明，当我们使用有限的雄性不育个体育种材料生产双同源时，通过使用一对亲缘性较低的双异源进行人工杂交可能避免近交抑制的不利影响。