1). This topology was identical to the classification based on their morphology and habits [10], [18], [19], [20], [21], [22] and [23]. Pairwise distances are shown in Table S3. The UBE3 sequence dataset was employed for construction of the nucleotide molecular formulae (NMF). The 724 bp aligned sequence corresponds to the DNA tract from bases 15 to 738 of the entire sequence of the UBE3 fragment from the 5′ end and includes all the variable sites of this region ( Table 2; Fig. S1). The position number of each variable site used in the formula was determined according to the newly generated 724 bp-length sequence alignment.

The ten polymorphic base sites used in the NMF of the taxa for the genus Juglans are No. 42, 85, 125, 205, 227, 322, 457, 459, 595 and 663 ( Table 2; Fig. S1). For instance, “Nuclear_DNA_UBE3_cds” was used to refer to the coding region of the nuclear UBE3 gene employed in the NMF and “aln_724 bp” refers to the aligned Talazoparib sequence length (724 bp) of BMS-354825 in vivo the nine representative species/variety/cultivars

in Juglans L. As a result, “Nuclear_DNA_UBE3_cds_aln_724bp_ ” can be constructed as an NMF for molecularly characterizing the cultivar Juglans regia ‘Zha 343’, with the figure following the nucleotide character indicating the position of the corresponding polymorphic base site from the 5′ end of the aligned sequence [24]. The NMF can be constructed in a similar way for the rest of the samples of the genus Juglans and the outgroups. “Nuclear DNA_UBE3_cds_aln_724bp_” is omitted to save space in the description below. “Type ”, for example, in the following next taxonomic key, refers to the taxon/taxa with –typed base mutation, i.e., nucleotide A can be detected at base position 42 from the 5′ end in the UBE3 region. Other types of base mutation are indicated in the same way. As shown in Fig. 2, a novel taxonomic key based on nucleotide molecular formulae is constructed by which the molecular feature of each taxon is given. Plants of Juglans sect. Cardiocaryon are precious tree species for high quality wood production. J. mandshurica and J.cathayensis are closely related taxa in Juglans sect. Cardiocaryon.

J. mandshurica is mostly distributed in provinces of North and Northeast China, where the climate is colder. J. cathayensis is mainly distributed in warmer provinces of South and Southwest China [19], [20] and [23]. The four black walnut species of Juglans sect. Rhysocaryon are closely related with each other, with some presence in North America as well [18], [19], [20], [21], [22] and [23]. Members of Juglans sect. Juglans are economically important tree species for edible walnut production. The distribution of Juglans sigillata and J. sigillata ‘Lushui 1Hao’ is limited to Southwest China (mainly Yunnan Province) [19], [20] and [23]. J. sigillata ‘Lushui 1 Hao’ is a traditional local cultivar with an annual nut production of more than 1.0 × 108 kg. In contrast, the annual nut production of J.