Table_2_Comparing adventitious root-formation and graft-unification abilities in clones of Argania spinosa.xlsx

Argania spinosa trees have attracted attention in recent years due to their high resistance to extreme climate conditions. Initial domestication activities practiced in Morocco. Here we report on selection and vegetative propagation of A. spinosa trees grown in Israel. Trees yielding relatively high amounts of fruit were propagated by rooting of stem cuttings. High variability in rooting ability was found among the 30 clones selected. In-depth comparison of a difficult-to-root (ARS7) and easy-to-root (ARS1) clone revealed that the rooted cuttings of ARS7 have a lower survival rate than those of ARS1. In addition, histological analysis of the adventitious root primordia showed many abnormal fused primordia in ARS7. Hormone profiling revealed that while ARS1 accumulates more cytokinin, ARS7 accumulates more auxin, suggesting different auxin-to-cytokinin ratios underlying the different rooting capabilities. The hypothesized relationship between rooting and grafting abilities was addressed. Reciprocal grafting was performed with ARS1/ARS7 but no significant differences in the success of graft unification between the trees was detected. Accordingly, comparative RNA sequencing of the rooting and grafting zones showed more differentially expressed genes related to rooting than to grafting between the two trees. Clustering, KEGG and Venn analyses confirmed enrichment of genes related to auxin metabolism, transport and signaling, cytokinin metabolism and signaling, cell wall modification and cell division in both regions. In addition, the differential expression of some key genes in ARS1 vs. ARS7 rooting zones was revealed. Taken together, while both adventitious root-formation and graft-unification processes share response to wounding, cell reprogramming, cell division, cell differentiation and reconnection of the vasculature, there are similar, but also many different genes regulating the two processes. Therefore an individual genotype can have low rooting capacity but good graft-unification ability.

近年来，阿甘树（Argania spinosa）因其对极端气候条件的极强抗性而受到广泛关注。其早期驯化活动始于摩洛哥。本研究针对以色列境内种植的阿甘树开展了选育与无性繁殖相关工作。我们选取挂果量相对较高的植株，通过茎段扦插生根的方式进行繁殖。在筛选出的30个无性系中，植株的生根能力存在显著差异。对难生根无性系ARS7与易生根无性系ARS1的深入对比分析表明，ARS7扦插苗的成活率显著低于ARS1。此外，对不定根原基（adventitious root primordia）的组织学分析显示，ARS7中存在大量异常融合的原基。激素谱分析结果显示，ARS1中积累更多细胞分裂素（cytokinin），而ARS7中生长素（auxin）含量更高，这表明不同的生长素/细胞分裂素比例是导致二者生根能力差异的潜在机制。

本研究还探究了生根能力与嫁接亲和性之间的潜在关联。对ARS1与ARS7开展正反嫁接实验，但未检测到二者在嫁接愈合成功率上存在显著差异。据此，对生根位点与嫁接位点的比较转录组测序分析显示，两个无性系间与生根相关的差异表达基因数量多于与嫁接相关的差异表达基因。聚类分析、京都基因与基因组百科全书（KEGG）富集分析以及韦恩（Venn）图分析均证实，在两个位点区域中，均富集到与生长素代谢、运输及信号转导、细胞分裂素代谢及信号转导、细胞壁修饰以及细胞分裂相关的基因。此外，研究还发现ARS1与ARS7生根位点区域中存在多个关键基因的差异表达。

综上，尽管不定根形成与嫁接愈合过程均涉及伤响应、细胞重编程、细胞分裂、细胞分化以及维管束重建等生物学过程，但调控这两个过程的基因既有共性，也存在大量差异。因此，单个基因型的植株可能生根能力较弱，但嫁接亲和性良好。