Kakui Hiroyuki, Tsurisaki Eriko, Shibata Rei, Moriguchi Yoshinari
Graduate School of Science and Technology, Niigata University, Niigata City, Niigata 950-2181, Japan.
Faculty of Agriculture, Niigata University, Niigata City, Niigata 950-2181, Japan.
Plants (Basel). 2021 Apr 23;10(5):856. doi: 10.3390/plants10050856.
Japanese cedar () is the most important timber species in Japan; however, its pollen is the primary cause of pollinosis in Japan. The total number of pollen grains produced by a single tree is determined by the number of male strobili (male flowers) and the number of pollen grains per male strobilus. While the number of male strobili is a visible and well-investigated trait, little is known about the number of pollen grains per male strobilus. We hypothesized that genetic and environmental factors affect the pollen number per male strobilus and explored the factors that affect pollen production and genetic variation among clones. We counted pollen numbers of 523 male strobili from 26 clones using a cell counter method that we recently developed. Piecewise Structural Equation Modeling (pSEM) revealed that the pollen number is mostly affected by genetic variation, male strobilus weight, and pollen size. Although we collected samples from locations with different environmental conditions, statistical modeling succeeded in predicting pollen numbers for different clones sampled from branches facing different directions. Comparison of predicted pollen numbers revealed that they varied >3-fold among the 26 clones. The determination of the factors affecting pollen number and a precise evaluation of genetic variation will contribute to breeding strategies to counter pollinosis. Furthermore, the combination of our efficient counting method and statistical modeling will provide a powerful tool not only for Japanese cedar but also for other plant species.
日本柳杉（Cryptomeria japonica）是日本最重要的木材树种；然而，其花粉是日本花粉症的主要病因。单棵树产生的花粉粒总数由雄球花（雄花）的数量和每个雄球花的花粉粒数量决定。虽然雄球花的数量是一个可见且研究充分的性状，但对于每个雄球花的花粉粒数量却知之甚少。我们假设遗传和环境因素会影响每个雄球花的花粉数量，并探究了影响花粉产量以及无性系间遗传变异的因素。我们使用最近开发的细胞计数法对来自26个无性系的523个雄球花的花粉数量进行了计数。分段结构方程模型（pSEM）显示，花粉数量主要受遗传变异、雄球花重量和花粉大小的影响。尽管我们从具有不同环境条件的地点采集了样本，但统计模型成功预测了从不同方向的树枝上采集的不同无性系的花粉数量。预测花粉数量的比较显示，26个无性系之间的差异超过3倍。确定影响花粉数量的因素并精确评估遗传变异将有助于制定应对花粉症的育种策略。此外，我们高效的计数方法与统计模型的结合不仅将为日本柳杉，也将为其他植物物种提供一个强大的工具。
