**Abstract**

North America is a center of diversity for *Prunus* species. Tree architecture, chilling requirement, heat requirement, fruit development period, fruit size, fruit texture, disease resistance, and adaptive changes to multiple environmental conditions are a few examples of the traits of which tremendous genetic variability is available in the native plum species. Wild native *Prunus* species constitute an important potential source of genetic diversity for stone fruit breeding and selection. A review of the North American plum taxonomic treatment and phylogenetic studies is described. Various studies have been done with three major groups being identified: Americana series, Chickasaw series, and Beach series.

**Keywords:** plums, phylogeny, taxonomy, *Prunus*, *Prunocerasus*

#### **1. Introduction**

The genus *Prunus* L. belongs to the subfamily Amygdaloideae (=Prunoideae) of the Rosaceae. It has a worldwide distribution with approximately 200 species. Edible species are mostly distributed in the northern hemisphere [1–5]. The genus contains species that are important in the production of fruit, nuts, and lumber. Plums, cherries, almonds, apricots, and peaches are the most commonly known fruit and nuts in this genus. The world's net production of almonds, apricots, cherries, peaches, nectarines, plums, and sloes in 2010 was approximately 40.8 million tons. Peach and nectarine production was the largest in the world with 20.5 million tons. US peach and nectarine production was approximately 1.3 million tons, with a farm gate value of 683 million dollars [6].

North America is an important center of diversity for plum species adapted (native) to widely divergent climates and soils representing an important potential source of genes for plant breeding. In [7], Layne and Bassi reported high levels of variation in the *Prunus* germplasm for tree size, growth habit, flower size and color, chill hour requirement, fruit size, flesh texture, flesh color, resistance to diseases, and adaptability to diverse climatic and geographic regions. Plums are the stone fruit with the greatest diversity of flavor, aroma, texture, color, form, and size [2, 8].

Stone fruit breeders have used this tremendous genetic variability through interspecific hybridizations (in particular with species in the subgenus *Prunus* or *Prunophora*) for the improvement of *Prunus* scion and rootstock cultivars [9]. Among those, native North American plum species have been identified as a source of resistance to blossom blight and brown rot (*Monilinia fructicola*), bacterial spot (*Xanthomonas campestris* pv. *pruni*), bacterial canker (*Pseudomonas syringae* pv. *syringae*), plum leaf scald (*Xylella fastidiosa*), peach tree short life (PTSL), root-knot nematode (*Meloidogyne* spp.), lesion nematode (*Pratylenchus* spp.), clitocybe root rot (*Armillaria tabescens*), and others [9–12].

**Group Species Origin Cultivation**

Eastern Europe and west-central Asia Nova Scotia,

China New York,

China, Japan Maine,

USA (Ohio, Texas, northward to Minnesota and Montana)

CAN (Newfoundland west to Rainy and Assiniboine rivers), USA (New England

USA (standing between *P. americana* and

USA (Southern range to Delaware and Kentucky, including southern Atlantic

USA (South and southeast Nebraska and central and western Kansas)

USA (sea beaches, New Brunswick to Virginia, Georgia, Alabama, and

USA (Colorado, Guadalupe, and the Leona) North of

USA (the Mississippi valley) From Texas to

USA (Pacific coast) Sierra regions of

the Wildgoose group)

and Gulf states)

Connecticut)

central New England, New York, southern Ontario and Michigan, and the Pacific coast states

Europe and US used as rootstock

California

Vermont, Ontario, and southern Iowa

Prince Edward Island, Manitoba, and Vancouver, to Florida, Louisiana, and Texas

Prince Edward Island, Manitoba, and Vancouver, to Florida, Louisiana, and Texas

Not cultivated

Burlington, Vermont, and Iowa

Massachusetts

Iowa, Vermont, New York, and Massachusetts

Cultivated by settlers in Kansas and Maryland

Not cultivated

California and southern Oregon

Cultivated Domestica plums

*Prunus domestica*

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

*domestica*

*Prunus cerasifera*

*Prunus simonii*

*Prunus triflora*

*Prunus americana*

*Prunus americana nigra*

*Prunus hortulana mineri*

*Prunus rivularis*<sup>z</sup> *Prunus hortulana*<sup>y</sup>

*Prunus hortulana*

*angustifolia*

*angustifolia watsonii*

*Prunus maritima*

*Prunus subcordata* Europe

states)

Damsons *Prunus*

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

Myrobalan plums

Simon plums

Japanese plums

Indigenous Americana group

> Nigra group

Miner Group

Wayland group

Wildgoose group

Beach plum

Pacific plum

**29**

Chickasaws *Prunus*

Sand plum *Prunus*

Resistance to bacterial leaf spot and bacterial canker was identified in a cultivar derived from *P. salicina* Lindl., *P. cerasifera* Ehrh., *P. angustifolia* Marshall, *P. americana* Marshall, and *P. munsoniana* W. Wight & Hedrick. *Prunus hortulana* L.H. Bailey was found resistant to root-knot nematode and has been recommended as a rootstock for European plums. Improved tolerance for PTSL was found in hybrids from *P. americana*, *P. hortulana*, *P. angustifolia*, and/or *P. umbellata* Elliot. Potential uses of the native North American plum species as breeding parents, scions, and/or rootstocks were summarized by [10, 12].

#### **2. Taxonomic treatment**

In [8], Waugh described the genus *Prunus* as trees or shrubs, mostly with edible fruit and flowers, white or pink, with spreading petals. Stamens 15–30, distinct, with filiform filaments. Style, terminal; stigma, usually truncate. The fruit has a fleshy exterior, is glabrous, and contains a hard bony pit, which contains the seed.

Inconsistencies in the taxonomy of *Prunus* were recognized by Waugh [8] and Hedrick [2]. Bortiri et al. [1] summarized the classification discrepancies in *Prunus* as follows: (1) four different genera (*Amygdalus*, *Cerasus*, *Prunus*, and *Padus* [13]) and later two (*Amygdalus* and *Prunus*) [14]; (2) five genera (*Amygdalus*, *Persica*, *Prunus*, *Armeniaca*, and *Cerasus* (including *Padus* and *Laurocerasus*)) [15]; (3) *Prunus* as a single genus divided in seven sections (*Amygdalus*, *Armeniaca*, *Prunus*, *Cerasus*, *Laurocerasus*, *Ceraseidos*, and *Amygdalopsis*) [16]; (4) *Prunus* with previous seven sections as subgenera [17]; (5) *Prunus* classified into five subgenera (*Prunophora* (*Prunus*), *Amygdalus*, *Cerasus*, *Padus*, and *Laurocerasus*) and with subgenus *Prunus* divided in three sections (*Euprunus*, *Prunocerasus*, and *Armeniaca*) [3]; and (6) *Prunus* divided into three genera (*Padus*, *Laurocerasus*, and *Prunus*) [18].

Recently, the concept of *Prunus* as single genus has become widely accepted, but subgenera classification is still undistinguished as new phylogenetic relationships within *Prunus* come to light. The USDA-GRIN [19] germplasm collection organizes the genus *Prunus* into subgenus *Amygdalus*, *Cerasus*, *Emplectocladus*, and *Prunus*. Subgenus *Cerasus* was divided into sections *Cerasus* and *Laurocerasus* and subgenus *Prunus* into sections *Armeniaca*, *Microcerasus* (including some plums), *Penarmeniaca*, *Prunocerasus* (the North American plums), and *Prunus*.

Waugh [8] recognized the difficulty in classifying the North American plums and stated "plums grow pretty much as they please, and the botanist has to take them as he finds them." The distribution, cultivation, hybridization, and breeding value of native plums have been extensively studied [2, 4, 5, 8, 20, 21].

Waugh [8] classified the cultivated and indigenous *Prunus* of North America into groups. These groups were clustered into seven series: Americana, Chickasaw, Hortulana, Maritima, Sand Cherry, Choke Cherry, and Black Cherry [22] (**Table 1**). The Americana series included the Americana group (including *P. americana* var. *lanata*) and the Nigra group (*Prunus nigra* Aiton). The Chickasaw series included the Chickasaw and the Sand plum groups. The Hortulana series, categorized as "hybrids," included the Wildgoose group, the Wayland group, and the Miner


*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic… DOI: http://dx.doi.org/10.5772/intechopen.91638*

*Prunophora*) for the improvement of *Prunus* scion and rootstock cultivars [9]. Among those, native North American plum species have been identified as a source of resistance to blossom blight and brown rot (*Monilinia fructicola*), bacterial spot (*Xanthomonas campestris* pv. *pruni*), bacterial canker (*Pseudomonas syringae* pv. *syringae*), plum leaf scald (*Xylella fastidiosa*), peach tree short life (PTSL), root-knot nematode (*Meloidogyne* spp.), lesion nematode (*Pratylenchus* spp.), clitocybe root

Resistance to bacterial leaf spot and bacterial canker was identified in a cultivar derived from *P. salicina* Lindl., *P. cerasifera* Ehrh., *P. angustifolia* Marshall, *P. americana* Marshall, and *P. munsoniana* W. Wight & Hedrick. *Prunus hortulana* L.H. Bailey was found resistant to root-knot nematode and has been recommended as a rootstock for European plums. Improved tolerance for PTSL was found in hybrids from *P. americana*, *P. hortulana*, *P. angustifolia*, and/or *P. umbellata* Elliot. Potential uses of the native North American plum species as breeding parents, scions, and/or

In [8], Waugh described the genus *Prunus* as trees or shrubs, mostly with edible fruit and flowers, white or pink, with spreading petals. Stamens 15–30, distinct, with filiform filaments. Style, terminal; stigma, usually truncate. The fruit has a fleshy exterior, is glabrous, and contains a hard bony pit, which contains the seed. Inconsistencies in the taxonomy of *Prunus* were recognized by Waugh [8] and Hedrick [2]. Bortiri et al. [1] summarized the classification discrepancies in *Prunus* as follows: (1) four different genera (*Amygdalus*, *Cerasus*, *Prunus*, and *Padus* [13]) and later two (*Amygdalus* and *Prunus*) [14]; (2) five genera (*Amygdalus*, *Persica*, *Prunus*, *Armeniaca*, and *Cerasus* (including *Padus* and *Laurocerasus*)) [15]; (3) *Prunus* as a single genus divided in seven sections (*Amygdalus*, *Armeniaca*, *Prunus*,

*Cerasus*, *Laurocerasus*, *Ceraseidos*, and *Amygdalopsis*) [16]; (4) *Prunus* with

*Prunus* into sections *Armeniaca*, *Microcerasus* (including some plums), *Penarmeniaca*, *Prunocerasus* (the North American plums), and *Prunus*.

value of native plums have been extensively studied [2, 4, 5, 8, 20, 21].

previous seven sections as subgenera [17]; (5) *Prunus* classified into five subgenera (*Prunophora* (*Prunus*), *Amygdalus*, *Cerasus*, *Padus*, and *Laurocerasus*) and with subgenus *Prunus* divided in three sections (*Euprunus*, *Prunocerasus*, and

Recently, the concept of *Prunus* as single genus has become widely accepted, but subgenera classification is still undistinguished as new phylogenetic relationships within *Prunus* come to light. The USDA-GRIN [19] germplasm collection organizes the genus *Prunus* into subgenus *Amygdalus*, *Cerasus*, *Emplectocladus*, and *Prunus*. Subgenus *Cerasus* was divided into sections *Cerasus* and *Laurocerasus* and subgenus

Waugh [8] recognized the difficulty in classifying the North American plums and stated "plums grow pretty much as they please, and the botanist has to take them as he finds them." The distribution, cultivation, hybridization, and breeding

Waugh [8] classified the cultivated and indigenous *Prunus* of North America into groups. These groups were clustered into seven series: Americana, Chickasaw, Hortulana, Maritima, Sand Cherry, Choke Cherry, and Black Cherry [22] (**Table 1**). The Americana series included the Americana group (including *P. americana* var. *lanata*) and the Nigra group (*Prunus nigra* Aiton). The Chickasaw series included the Chickasaw and the Sand plum groups. The Hortulana series, categorized as "hybrids," included the Wildgoose group, the Wayland group, and the Miner

*Armeniaca*) [3]; and (6) *Prunus* divided into three genera (*Padus*, *Laurocerasus*,

rot (*Armillaria tabescens*), and others [9–12].

rootstocks were summarized by [10, 12].

**2. Taxonomic treatment**

Prunus

and *Prunus*) [18].

**28**


classifications [3]. *Prunus persica* L.-*P. dulcis* (Mill.) D.A. Webb, *P. domestica* L.*-P.*

In Bortiri et al. [1] the phylogeny and systematics of *Prunus* based on ITS and chloroplast *trnL-trnF* spacer DNA sequences identified two major clades: subgenera *Padus-Laurocerasus*-*Cerasus* and subgenera *Prunus*-*Amygdalus*-*Emplectocladus*-*Cerasus* (sect. *Microcerasus*)-sect. *Penarmeniaca* (similar to Mowrey and Werner [23], Lee and Wen [27], and Bortiri et al. [1]). Their results indicated that plums of northeastern North America were closely related and that *P. mexicana* belonged to a

sorbitol-6-phosphate dehydrogenase, to assess the lack of support for deep nodes in the clade subgenera *Prunus-Amygdalus-Emplectocladus* (as reported in previous data). The phylogenies based on ITS, cpDNA *trnL-trnF*, and *s6pdh* sequences were compared and combined. Phylogenetic analysis of the combined data supported two major clades: subgenera *Cerasus-Laurocerasus-Padus* and subgenera *Amygdalus-Emplectocladus-Prunus*. Section *Microcerasus* (subgenera *Cerasus*) was reported

*Prunus* subg. *Prunus* sect. *Prunocerasus* was reported to be monophyletic by Shaw

Similarly, a survey of cpDNA haplotypes available within section *Prunocerasus* was reported by Shaw and Small [30]. The cpDNA *rpL*16 region was sequenced for 207 accession representatives of 17 North American plums, including *P. texana* D. Dietr. (as described before). More than one of the three primary cpDNA

Bortiri et al. [31] studied the evolution of vegetative and morphological characters of 37 species of *Prunus* and other genera of Rosaceae. Morphological characters were combined with ITS, *trn*L-*trn*F, and *trn*S-*trn*G data from previous studies [1, 28]. The addition of the morphological data with *trn*S-*trn*G supported some nodes that were found in ITS and *trn*L-*trn*F studies. Three clades were reported: "Clade A" with subgenera *Padus* and *Laurocerasus*; "Clade B" with subgenera *Amygdalus*, *Emplectocladus*, and *Prunus*; and "Clade C" with subgenera *Cerasus*. "Clade B" was characterized by the production of three axillary buds. *Padus* and

Genetic diversity within *Prunus cerasifera* (cherry plum) was studied using morphological characters, cytometry, cpDNA, and SSR markers [32]. Morphological characters showed differences between clones. Analysis of cpDNA reported 15 haplotypes clustered in 3 groups. Considerable diversity among accessions was

*Laurocerasus* were not supported as monophyletic (high homoplasy).

and Small [29]. The phylogenetic analysis was based on seven cpDNA regions: *rp*S16, *rp*L16, *trn*L, *trn*G, *trn*L*-trn*F, *trn*S*-trn*G, and *trn*H*-psb*A. Three clades were strongly supported in sect. *Prunocerasus*: the "American Clade," the "Chickasaw Clade," and the "Beach Clade" (names based on Waugh's (1901) classification). The American clade included *P. americana* Marshall var. *americana* Sudw., *P. americana* Marshall var. *lanata*, *P. mexicana*, *P. rivularis* Scheele, *P. hortulana*, and *P. umbellata* var. *injucunda*; the Chickasaw clade included *P. angustifolia*, *P. munsoniana*, *P. gracilis* Engelm. & A. Gray, *P. nigra*, *P. umbellata* Elliot var. *umbellata*, *P. alleghaniensis* Porter var. *alleghaniensis*, and *P. alleghaniensis* Porter var. *davisii* (W. Wight) Sarg.; and the Beach clade included *P. geniculata* Harper, *P. maritima* Marshall var. *maritima*, and *P. maritima* Marshall var. *gravesii* (Small)


Lee and Wen's [27] phylogenetic analysis of the genus *Prunus* using ITS sequences recognized two major groups: the *Amygdalus*-*Prunus* group, and the *Cerasus*-*Laurocerasus*-*Padus* group. The results were not congruent with Rehder's [3]

Bortiri et al. [28] used the nuclear gene *s6pdh*, which encodes NADP<sup>+</sup>

*salicina* Lindl., and *P. cerasus* L.*-P. fruticosa* Pall were monophyletic.

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

taxonomic treatment.

nested within subgenus *Prunus*.

haplotypes was found in many of the taxa.

reported based on these studies.

**31**

sister clade.

G.J. Anderson.

*Classified as* Prunus rivularis *but with doubts. <sup>y</sup>* Prunus hortulana *consider as part of the Wayland and the Wildgoose group.*

#### **Table 1.**

*z*

*Cultivated and indigenous plums in North America by group, area of origin, and cultivation [8].*

group. The Maritima series the Beach plum group, the Southern sloe group [including *P. umbellata* Elliot var. *injuncunda* (Small) Sarg.], the Oklahoma plum group, and *P. glandulosa* Thunb. (ungrouped). The Sand Cherry series were equivalent to the Dwarf cherries group. The Choke Cherry and the Black Cherry series conserved their name as groups [8, 22] (**Table 1**).

Wight [5] separated the genus *Prunus* in plums, cherries, and dwarf cherries. Waugh's [8, 22] taxonomic treatment included cherries as part of plums. Wight's [5] groups/series were Americana, Subcordata, Hortulana, Angustifolia, Maritima, and Gracilis. The Angustifolia group agreed with Waugh's [22] Chickasaw series. Waugh [22] did not include *P. mexicana S. Watson* (Americana group), *P. munsoniana* (Angustifolia group), *P. subcordata* Benth. (Subcordata group), *P. alleghaniensis* Porter (Maritima group), and *P. umbellata* (Maritima group), as part of his groups/series.

#### **3.** *Prunus* **phylogenetic studies**

Phylogeny and systematics in the genus *Prunus* was reported by [23]. They employed isozymes to study the phylogenetic relationships in *Prunus*. Section *Prunocerasus* was found to be polyphyletic, with a clade formed by *P. americana*, *P. munsoniana*, *P. hortulana*, *P. subcordata*, and *P. angustifolia*, and a clade formed by *P. maritima* Marshall and *P. umbellata*.

Chloroplast DNA is an alternative source of genetic variation and is maternally inherited in *Prunus*. Chloroplast DNA is highly conserved and in relative abundance in the cell as compared with the nuclear DNA. Kaneko et al. [24] and Uematsu et al. [25] used cpDNA to classify cherries, apricots, and wild and cultivated peaches in Japan. In [26], Badenes and Parfitt reported a phylogeny similar to Mowrey and Werner [23]. All the *Prunus* species were grouped as in conventional subgenus

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic… DOI: http://dx.doi.org/10.5772/intechopen.91638*

classifications [3]. *Prunus persica* L.-*P. dulcis* (Mill.) D.A. Webb, *P. domestica* L.*-P. salicina* Lindl., and *P. cerasus* L.*-P. fruticosa* Pall were monophyletic.

Lee and Wen's [27] phylogenetic analysis of the genus *Prunus* using ITS sequences recognized two major groups: the *Amygdalus*-*Prunus* group, and the *Cerasus*-*Laurocerasus*-*Padus* group. The results were not congruent with Rehder's [3] taxonomic treatment.

In Bortiri et al. [1] the phylogeny and systematics of *Prunus* based on ITS and chloroplast *trnL-trnF* spacer DNA sequences identified two major clades: subgenera *Padus-Laurocerasus*-*Cerasus* and subgenera *Prunus*-*Amygdalus*-*Emplectocladus*-*Cerasus* (sect. *Microcerasus*)-sect. *Penarmeniaca* (similar to Mowrey and Werner [23], Lee and Wen [27], and Bortiri et al. [1]). Their results indicated that plums of northeastern North America were closely related and that *P. mexicana* belonged to a sister clade.

Bortiri et al. [28] used the nuclear gene *s6pdh*, which encodes NADP<sup>+</sup> -dependent sorbitol-6-phosphate dehydrogenase, to assess the lack of support for deep nodes in the clade subgenera *Prunus-Amygdalus-Emplectocladus* (as reported in previous data). The phylogenies based on ITS, cpDNA *trnL-trnF*, and *s6pdh* sequences were compared and combined. Phylogenetic analysis of the combined data supported two major clades: subgenera *Cerasus-Laurocerasus-Padus* and subgenera *Amygdalus-Emplectocladus-Prunus*. Section *Microcerasus* (subgenera *Cerasus*) was reported nested within subgenus *Prunus*.

*Prunus* subg. *Prunus* sect. *Prunocerasus* was reported to be monophyletic by Shaw and Small [29]. The phylogenetic analysis was based on seven cpDNA regions: *rp*S16, *rp*L16, *trn*L, *trn*G, *trn*L*-trn*F, *trn*S*-trn*G, and *trn*H*-psb*A. Three clades were strongly supported in sect. *Prunocerasus*: the "American Clade," the "Chickasaw Clade," and the "Beach Clade" (names based on Waugh's (1901) classification). The American clade included *P. americana* Marshall var. *americana* Sudw., *P. americana* Marshall var. *lanata*, *P. mexicana*, *P. rivularis* Scheele, *P. hortulana*, and *P. umbellata* var. *injucunda*; the Chickasaw clade included *P. angustifolia*, *P. munsoniana*, *P. gracilis* Engelm. & A. Gray, *P. nigra*, *P. umbellata* Elliot var. *umbellata*, *P. alleghaniensis* Porter var. *alleghaniensis*, and *P. alleghaniensis* Porter var. *davisii* (W. Wight) Sarg.; and the Beach clade included *P. geniculata* Harper, *P. maritima* Marshall var. *maritima*, and *P. maritima* Marshall var. *gravesii* (Small) G.J. Anderson.

Similarly, a survey of cpDNA haplotypes available within section *Prunocerasus* was reported by Shaw and Small [30]. The cpDNA *rpL*16 region was sequenced for 207 accession representatives of 17 North American plums, including *P. texana* D. Dietr. (as described before). More than one of the three primary cpDNA haplotypes was found in many of the taxa.

Bortiri et al. [31] studied the evolution of vegetative and morphological characters of 37 species of *Prunus* and other genera of Rosaceae. Morphological characters were combined with ITS, *trn*L-*trn*F, and *trn*S-*trn*G data from previous studies [1, 28]. The addition of the morphological data with *trn*S-*trn*G supported some nodes that were found in ITS and *trn*L-*trn*F studies. Three clades were reported: "Clade A" with subgenera *Padus* and *Laurocerasus*; "Clade B" with subgenera *Amygdalus*, *Emplectocladus*, and *Prunus*; and "Clade C" with subgenera *Cerasus*. "Clade B" was characterized by the production of three axillary buds. *Padus* and *Laurocerasus* were not supported as monophyletic (high homoplasy).

Genetic diversity within *Prunus cerasifera* (cherry plum) was studied using morphological characters, cytometry, cpDNA, and SSR markers [32]. Morphological characters showed differences between clones. Analysis of cpDNA reported 15 haplotypes clustered in 3 groups. Considerable diversity among accessions was reported based on these studies.

group. The Maritima series the Beach plum group, the Southern sloe group [including *P. umbellata* Elliot var. *injuncunda* (Small) Sarg.], the Oklahoma plum group, and *P. glandulosa* Thunb. (ungrouped). The Sand Cherry series were equivalent to the Dwarf cherries group. The Choke Cherry and the Black Cherry series conserved

*Cultivated and indigenous plums in North America by group, area of origin, and cultivation [8].*

**Group Species Origin Cultivation**

USA (Alleghany mountains in

Louisiana, and Arkansas)

Tennessee)

Pennsylvania)

North Carolina)

and Colorado)

USA (Southern Kansas to Texas and

USA (seashore from South Carolina to Florida and westward to Mississippi,

*P. pumila* in USA (coasts of northern states), *P. pumila* besseyi (from Manitoba to Kansas, westward to California and Utah), and *P. cuneata* in USA (New Hampshire to Minnesota and southward to

CAN (Newfoundland to Manitoba and British Columbia) to USA (Georgia, Texas,

CAN (Quebec) to USA (Kansas and southward, New Mexico, and Mexico) Not cultivated

Not cultivated

Not cultivated

Not cultivated

Not cultivated

Nebraska eastward

Wight [5] separated the genus *Prunus* in plums, cherries, and dwarf cherries. Waugh's [8, 22] taxonomic treatment included cherries as part of plums. Wight's [5] groups/series were Americana, Subcordata, Hortulana, Angustifolia, Maritima, and Gracilis. The Angustifolia group agreed with Waugh's [22] Chickasaw series. Waugh [22] did not include *P. mexicana S. Watson* (Americana group), *P. munsoniana* (Angustifolia group), *P. subcordata* Benth. (Subcordata group), *P. alleghaniensis* Porter (Maritima group), and *P. umbellata* (Maritima group), as part

Phylogeny and systematics in the genus *Prunus* was reported by [23]. They employed isozymes to study the phylogenetic relationships in *Prunus*. Section *Prunocerasus* was found to be polyphyletic, with a clade formed by *P. americana*, *P. munsoniana*, *P. hortulana*, *P. subcordata*, and *P. angustifolia*, and a clade formed by

Chloroplast DNA is an alternative source of genetic variation and is maternally inherited in *Prunus*. Chloroplast DNA is highly conserved and in relative abundance in the cell as compared with the nuclear DNA. Kaneko et al. [24] and Uematsu et al. [25] used cpDNA to classify cherries, apricots, and wild and cultivated peaches in Japan. In [26], Badenes and Parfitt reported a phylogeny similar to Mowrey and Werner [23]. All the *Prunus* species were grouped as in conventional subgenus

their name as groups [8, 22] (**Table 1**).

Oklahoma plum

Alleghany plum

Southern sloe

Dwarf cherries

Choke Cherry

Black Cherry

*Classified as* Prunus rivularis *but with doubts. <sup>y</sup>*

*z*

**Table 1.**

Prunus

*Prunus gracilis*

*Prunus alleghaniensis*

*Prunus umbellata*

*Prunus pumila Prunus pumila besseyi Prunus cuneata*

*Prunus virginiana*

*Prunus serotina*

Prunus hortulana *consider as part of the Wayland and the Wildgoose group.*

**3.** *Prunus* **phylogenetic studies**

*P. maritima* Marshall and *P. umbellata*.

of his groups/series.

**30**


**Paper Badenes and Parfitt [26] Lee and Wen [27]**

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

Support for subgenus *Prunus*, *Cerasus*, and *Amygdalus*. Relative small number of taxa used in the study. Subgenus *Cerasus* suggested to be more extensively evolved than either *Prunus* or *Amygdalus*

**Paper Bortiri et al. [1] Bortiri et al. [28]**

ITS nuclear ribosomal DNA and chloroplast *trn*L-*trn*F spacer DNA

*Padus*, and *Laurocerasus* [3]

Outgroups *Exochorda racemosa*, *Oemleria cerasiformis*,

48 species/5 subgenus: *Prunus* (sect.: *Prunus, Prunocerasus, Armeniaca*), *Amygdalus*, *Cerasus* (sect.: *Microcerasus, Pseudocerasus, Mahaleb, Phyllomahaleb*),

*Prinsepia sinensis*, *Physocarpus capitatus*, *Sorbaria sorbifolia,* and *Spiraea cantoniensis*

Molecular Molecular

MP MP, ML

Characters (no.)

Informative characters (no.)

Substitutions (no.) Inversions (no.)

Percent variability

Phylogeny in classification

Phylogenetic analysis

Analytical methods

Metrics (analysis)

Taxa (no.)/ subgenus (sect.)

**33**

Trees (no.) 10 MP = 15,000 MPT (L = 630, CI = 0.632,

Indels (no.) 29 indels (>3 bp) aligned (ITS1 = 13 bp,

PIC 218 bp aligned (ITS1 = 114 bp, 5.8 s = 12 bp,

Notes Number of parsimony informative

23 662 bp aligned (ITS1 = 223–242 bp,

RC = 0.510). Consensus tree 16,383 MPTs (L = 630, CI = 0.632, RI = 0.808). ML tree

5.8 s = 154 bp, and ITS2 = 201–219 bp)

ITS2 = 92 bp) (not including indels)

32.9% aligned (ITS1 = 47.1%, 5.8 s = 7.79%,

Genus *Prunus* was monophyletic. Support for *Maddenia* nested within genus *Prunus*. Within genus *Prunus*, two major groups were recognizable: *Amygdalus*-*Prunus* group and *Cerasus-Laurocerasus-Padus* group

characters included outgroups. The % variability cannot be directly compared with studies that excluded the outgroups for

Nuclear gene sorbitol 6-phosphate dehydrogenase (*s6pdh*) and data from previous study ITS and *trn*L-*trn*F [1]

22 species (representing all the major clades found in previous study)/5 subgenus: *Prunus* (sect.: *Prunus, Prunocerasus, Armeniaca*), *Amygdalus, Cerasus* (sect.: *Microcerasus, Pseudocerasus, Mahaleb, Phyllomahaleb*), *Padus*, and

*Exochorda racemosa*, *Oemleria cerasiformis*, *Sorbaria sorbifolia, Spiraea cantoniensi, Holodiscus microphyllus*, *Chamaebatiaria millefolium*, *Kageneckia oblonga*, *Vauquelinia californica*, *Gillenia stipulata, Pyrus caucasica*, *Sorbus* sp., *Amelanchier alnifolia*, *Aruncus dioicus*, *Neilla sinensis*,

218 bp aligned (ITS1 = 114 bp, 5.8 s = 12 bp,

log likelihood = 3641.3155

and ITS2 = 92 bp)

ITS2 = 16 bp)

ITS2 = 42.0%)

the number of PICs

*Laurocerasus* [3]

and *Spiraea betulifolia*


*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic… DOI: http://dx.doi.org/10.5772/intechopen.91638*

**Paper<sup>z</sup> Kaneko et al. [24] Mowrey and Werner [23]**

Molecular Molecular

Trees (no.) 2 2 (average 30 principal components)

Notes *Lithocerasus* formed part of *Cerasus* in

Outgroups *Fragaria vesca Exochorda giraldii*, *Maddenia hypoleuca*,

**Paper Badenes and Parfitt [26] Lee and Wen [27]**

cpDNA cutting with 21 3.2 kb and 10

9 species/5 subgenus: *Prunus*, *Amygdalus*,

2.1 kb endonucleases

and *Cerasus.*

Molecular Molecular

MP MP, NJ, ML

Phenetics—principal components

34 species/4 subgenus: *Prunus* (sect.: *Prunus*, *Prunocerasus*, *Armeniaca*), *Amygdalus*, *Cerasus* (sect.: *Sargentiella*, *Microcalymma*, *Magniculpula*, *Phyllomahaleb*), and *Lithocerasus* (sect.: *Microcerasus*, *Armeniacocerasus*) [35]

Support for subgenus *Prunus.* Subgenus *Lithocerasus* was identified as an artificial

grouping of species

Rehder's [3] classification

ITS nuclear ribosomal DNA

subgenus: *Prunus* (sect.: *Prunus*, *Prunocerasus, Armeniaca*), *Amygdalus*, *Cerasus* (sect.: *Microcerasus*, *Pseudocerasus*, *Mahaleb*, *Phyllomahaleb*), *Padus*, and

*Laurocerasus* [3]

40 species (represented by 52 accessions)/5

*Oemleria cerasiformis*, *Prinsepia sinensis*, *Prinsepia uniflora*, *Lyonothamnus floribundus*

Isozyme

Phenetics—percent differential restriction fragments and Engel's

cpDNA using *BamH*I, *Hind*III,

11 species/3 subgenus: *Cerasus*, *Padus*, *Armeniaca* [3]/genus *Prunus*

genetic distance

and *Sma*I

Phylogenetic analysis

Prunus

Analytical methods

Metrics (analysis)

Taxa (no.)/ subgenus (sect.) genus

Outgroups

Characters or bp (no.) Informative characters (no.) Indels (no.) Substitutions (no.) Inversions (no.) PIC Percent variability Phylogeny in classification

Phylogenetic analysis

Analytical methods

Metrics (analysis)

**32**

Taxa (no.)/ subgenus (sect.)


**Paper Shaw and Small [29]**

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

*Prunocerasus* analysis introns: *trnL*UAA = 522 bp, *rpS*16 = 683 bp, *rpL*16 = 996 bp, and *trnG*UUC = 711 bp. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 703 bp, *trnL*UUA*trnF*GAA = 397 bp, and *trnH*GUG-*psbA* = 363 bp. Combined data = 4375 bp. *Prunus* analysis *trnH*GUG-*psbA* = 516 bp, *rpL*16 = 1105 bp, *trnS*GCU-*trnG*UUC = 903 bp,

and *trnG*UUC = 746 bp. Combined data = 3270 bp

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

*trnG*UUC = 4 bp. Combined data = 41 bp

*trnG*UUC = 32 bp. Combined data = 92 bp

*trnG*UUC = 0 bp. Combined data = 1 bp

*trnG*UUC = 36 bp. Combined data = 134 bp

*trnG*UUC = 4.80%. Combined data = 4.09%.

American, the Chickasaw, and the Beach clades

Notes *Prunus texana* was first used in this study. *Prunus texana* and *P. fasciculata* were not recognized by Waugh [8], Wight [5], and Rehder [3] **Paper Rohrer et al. [36] Shaw and Small [30] Katayama and Uematsu [37]**

Molecular Molecular Molecular

UPGMA MP UPGMA

A total of 207 accessions = 18 species (subgenus *Prunus* sect. *Prunocerasus*)

Indels (no.) *Prunocerasus* analysis introns: *trnL*UAA = 0 bp, *rpS*16 = 2 bp, *rpL*16 = 7 bp, and

Substitutions (no.) *Prunocerasus* analysis introns: *trnL*UAA = 1 bp, *rpS*16 = 4 bp, *rpL*16 = 6 bp, and

Inversions (no.) *Prunocerasus* analysis introns: *trnL*UAA = 0 bp, *rpS*16 = 0 bp, *rpL*16 = 0 bp, and

PIC *Prunocerasus* analysis introns: *trnL*UAA = 1 bp, *rpS*16 = 6 bp, *rpL*16 = 13 bp, and

Percent variability *Prunocerasus* analysis introns: *trnL*UAA = 0.19%, *rpS*16 = 0.88%, *rpL*16 = 1.31%,

*trnG*UUC = 0 bp. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 2 bp, *trnL*UUA*trnF*GAA = 0 bp, and *trnH*GUG-*psbA* = 3 bp. Combined data = 14 bp. *Prunus* analysis *trnH*GUG-*psbA* = 13 bp, *rpL*16 = 10 bp, *trnS*GCU-*trnG*UUC = 14 bp,

*trnG*UUC = 4 bp. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 4 bp, *trnL*UUA*trnF*GAA = 3 bp, and *trnH*GUG-*psbA* = 1 bp. Combined data = 23 bp. *Prunus* analysis *trnH*GUG-*psbA* = 11 bp, *rpL*16 = 21 bp, *trnS*GCU-*trnG*UUC = 28 bp, and

*trnG*UUC = 0 bp. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 0 bp, *trnL*UUA*trnF*GAA = 0 bp, and *trnH*GUG-*psbA* = 0 bp. Combined data = 0 bp. *Prunus* analysis *trnH*GUG-*psbA* = 0 bp, *rpL*16 = 0 bp, *trnS*GCU-*trnG*UUC = 1 bp, and

*trnG*UUC = 4 bp. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 6 bp, *trnL*UUA*trnF*GAA = 3 bp, and *trnH*GUG-*psbA* = 4 bp. Combined data = 37 bp. *Prunus* analysis *trnH*GUG-*psbA* = 24 bp, *rpL*16 = 31 bp, *trnS*GCU-*trnG*UUC = 43 bp, and

and *trnG*UUC = 0.56%. Intergeneric spacers: *trnS*GCU-*trn*GUUC = 0.85%, *trnL*UUA*trnF*GAA = 0.76%, and *trnH*GUG-*psbA* = 1.10%. Combined data = 37 bp. *Prunus* analysis *trnH*GUG-*psbA* = 4.65%, *rpL*16 = 2.80%, *trnS*GCU-*trnG*UUC = 4.76%, and

Genus *Prunus* was monophyletic. Subgenus *Prunus* sect. *Prunocerasus* and sect. *Prunus* were monophyletic. The genus *Prunus* was formed by two groups: subgenera *Laurocerasus-Padus* and subgenera *Amygdalus*-*Emplectocladus-Prunus-Cerasus*(sect. *Microcerasus*). *Prunus texana* and *P. subcordata* were included in sect. *Prunocerasus*. Within sect. *Prunocerasus* three groups were identified: the

*rpL*16 intron CpDNA analysis based on five

by RFLP

restriction enzymes (*Sal*I, *Xho*I, *Bam*HI, *Sac*I, and *Pst*I)

A total of 18 accessions = 14 *Prunus* species and 1 interspecific hybrid

Characters or bp

Informative characters (no.)

Phylogeny in classification

Phylogenetic analysis

Analytical methods

Metrics (analysis)

Taxa (no.)/ subgenus (sect.)/genus

**35**

Fifteen microsatellites primer pairs

18 species/subgenus *Prunus* sect. *Prunocerasus* (13 and 3 undetermined hybrids), subgenus *Prunus* (*P. cerasifera*), and

(no.)



**Paper Bortiri et al. [1] Bortiri et al. [28]**

*trn*L-*trn*F = 563 bp, ITS = 759 bp *s6pdh =* 1387 bp. Combined data

*trn*L-*trn*F = 4.62%, ITS = 10.01% *s6pdh* = 16.87%. For combined data

Metrics (analysis) Seven noncoding chloroplast DNA regions: *trnL*UAA, *rpS*16, *rpL*16, and *trnG*UUC

Trees (no.) Combined data set—MP = 25,171 MPT (L = 422, CI = 0.92, RI = 0.94)

introns; *trnS*GCU-*trn*GUUC; *trnL*UUA-*trnF*GAA; and *trnH*GUG-*psbA* intergeneric

43 species/5 subgenus: *Prunus* [sect.: *Prunus*, *Prunocerasus* (17 taxa), *Armeniaca*], *Amygdalus*, *Cerasus* (sect.: *Microcerasus*, *Pseudocerasus*, *Mahaleb*, *Phyllomahaleb*),

*s6pdh* sequence—MP = 273 MPT (L = 1198, CI = 0.58, RI = 0.81). s6pdh sequence—ML tree log likelihood = 7720.96. For combined data set—MP = 9 MPT (L = 1592, CI = 0.58, RI = 0.61). For combined data set—ML tree log likelihood = 12056.56

set = 2760 bp (*s6pdh, trn*L-*trn*F, and ITS)

*s6pdh =* 234 bp (excluding outgroups = among *Prunus* species). Combined data set = 226 bp (*s6pdh* = 148,

*trn*L-*trn*F = 18, and ITS = 60)

*s6pdh =* 234 bp (excluding outgroups = among *Prunus* species). Combined data set = 226 bp (s6pdh = 148,

*trn*L-*trn*F = 18, and ITS = 60)

(sect. *Microcerasus*)

set = 8.18% (*s6pdh* = 10.67%, *trn*L*trn*F = 3.19%, and ITS = 7.9% = calculated with characters from Bortiri et al. [1])

Genus *Prunus* was monophyletic. In the combined data set, the genus *Prunus* was formed by two groups: subgenera *Cerasus-Laurocerasus-Padus* and subgenera *Amygdalus-Emplectocladus-Prunus-Cerasus*

Includes *P. fasciculata* sect. *Emplectocladus*

(L = 187, CI = 0.733, RI = 0.834). ITS sequence—MP = stopped at 30000 MPT (L = 678, CI = 0.567, RI = 0.714). Combined data set—consensus tree 8318 MPT (L = 876, CI = 0.695, RI = 0.727)

*trn*L-*trn*F = 26 bp (excluding outgroups), ITS = 76 bp (excluding outgroups = among

Trees (no.) *trn*L-*trnF* sequence—MP = 76 MPT

*Prunus* species)

(>2 bp)

Indels (no.) *trn*L-*trn*F = 9 indels (>2 bp), ITS = 2 indels

PIC *trn*L-*trn*F = 26 bp (excluding outgroups),

Genus *Prunus* was monophyletic. *Exochorda*, *Oemleria*, and *Prinsepia* were not supported as sister groups with *Prunus*. Genus *Prunus* was divided in two clades: subgenera *Amygdalus*-*Prunus*-*Cerasus* (sect. *Microcerasus*)- *Emplectocladus* group and subgenera *Cerasus-Laurocerasus-Padus* group. Subgenus *Prunus* sect. *Prunus* was

*Emplectocladus*) was used in a study

*Padus*, and *Laurocerasus* [3]

monophyletic

**Paper Shaw and Small [29]**

Notes First time that *P. fasciculata* (sect.

Molecular

spacers

Outgroups *Physocarpus opulifolius*

ITS = 76 bp (excluding outgroups = among *Prunus* species) (not including indels)

Characters (no.)

Prunus

Informative characters (no.)

Substitutions (no.) Inversions (no.)

Percent variability

Phylogeny in classification

Phylogenetic analysis

Taxa (no.)/ subgenus (sect.)

**34**

Analytical methods MP, BI


**Paper Bortiri et al. [31] Wen et al. [38]**

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

Chloroplast *ndh*F region and ITS nuclear

A total of 59 (*ndh*F) or 51 (ITS) accessions of *Prunus*/5 subgenus: *Prunus* (sect.: *Prunus, Prunocerasus, Armeniaca*), *Amygdalus, Cerasus* (sect.: *Microcerasus, Pseudocerasus, Mahaleb*, *Phyllomahaleb*), *Padus*, and *Laurocerasus* [3]. In addition, *Madenia hypoleuca* and the *Pygeum* group

*Oemleria cerasiformis*, *Prinsepia uniflora*, *Physocarpus monogynus*, *Lyonothamnus floribundus*, and *Holodiscus discolor*

*ndh*F sequence—MP = 196,200 MPT (L = 815, CI = 0.71, COI = 056, RI = 0.86). ITS sequence—MP = 49,200 MPT (L = 791, CI = 0.56, COI = 0.45, RI = 0.70)

Both data set identified genus *Prunus* as a monophyletic group. Both data sets were incongruent at the species level in *Prunus*. The *ndh*F data supported two major groups: subgenera *Laurocerasus* (including *Pygeum*) and *Padus*, and subgenera *Amygdalus*, *Cerasus*, and *Prunus*. The ITS data supported a clade composed of subgenera *Amygdalus*, *Prunus,* and *Cerasus* sect. *Microcerasus*, and the paraphyletic clade of *Padus* and *Laurocerasus*

ribosomal gene.

ITS nuclear ribosomal gene, *trn*L-*trn*F spacer, *trn*S-*trn*G spacer, *trn*G intron, and

37 species/5 subgenus: *Prunus* (sect.: *Prunus*, *Prunocerasus*, *Armeniaca*), *Amygdalus*, *Cerasus* (sect.: *Microcerasus*, *Pseudocerasus*, *Mahaleb*, *Phyllomahaleb*),

*Spiraea cantoniensi, Gillenia stipulata, Lyonothamnus floribundus*, *Maddenia hypoleuca*, *Physocarpus capitatus*, *Physocarpus opulifolius*, and *Rhodotypos*

MPT (L = 110, CI = 0.36, RI = 0.73). Molecular data results from Bortiri et al. [1] and Bortiri et al. [28]. Combined data set—MP = 20 MPT (L = 1741, CI = 0.49, RI = 0.65). Combined data set—ML tree

ITS = 178 bp, *trn*L-*trn*F = 50 bp, and *trn*S-

25 morphological characters.

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

*Padus*, and *Laurocerasus* [3]

Outgroups *Oemleria cerasiformis*, *Sorbaria sorbifolia,*

Trees (no.) Morphological data set—MP = 50,000

log likelihood = 12499.63

*trn*G = 142 bp

*trn*G = 142 bp

homoplasy)

Indels (no.) Combined data set = 3

Combined data set = 771 bp

PIC ITS = 178 bp, *trn*L-*trn*F = 50 bp, and *trn*S-

Three clades were reported: "Clade A" with subgenera *Padus* and *Laurocerasus*; "Clade B" with subgenera *Amygdalus*, *Emplectocladus*, and *Prunus*; and "Clade C" with subgenera *Cerasus*. "Clade B" was characterized by the production of three axillary buds. *Padus* and *Laurocerasus* were not supported as monophyletic (highly

**Paper Depypere et al. [33] Chavez et al. [39]**

Morphology and molecular Molecular

UPGMA, PCo, and BI MP and ML

*scandens*

Metrics (analysis)

Taxa (no.)/ subgenus (sect.)/genus

Characters or bp (no.)

Informative characters (no.)

Substitutions (no.) Inversions (no.)

Percent variability Phylogeny in classification

Phylogenetic analysis

Analytical methods

**37**


*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic… DOI: http://dx.doi.org/10.5772/intechopen.91638*

**Paper Rohrer et al. [36] Shaw and Small [30] Katayama and Uematsu [37]**

(L = 34, CI = 0.97, RI = 0.99)

*rpL*16 intron = 797 bp

*rpL*16 intron = 23 bp

*rpL*16 intron = 2.88%

Twenty-two unique haplotypes were identified in sect. *Prunocerasus*. Ten different haplotypes were associated with the American clade, two haplotypes with the Beach clade, and seven haplotypes with the Chickasaw clade. Additionally, one Texana haplotype, one Subcordata haplotype, and one peculiar *Umbellata* haplotype

The common practice of choosing one specimen to represent a taxon can be misleading in closely related groups. Choosing different genotypes could have resulted in a different result than previous studies

*hondoensis*

Strict consensus = 8 MPT (L = 68, CI = 0.93, RI = 0.64)

Eleven genome types. The UPGMA tree consisted of two major groups: genome types A-I (subgenus *Amygdalus*, *Prunus*, and *Cerasus* sect. *Microcerasus*) and other with genomes J-K (subgenus *Laurocerasus* and *Padus*).

The 9.1 kb region between *psb*A and *atp*A genes would be useful tool to study the cpDNA evolution in *Prunus*

Outgroups *Pyrus ussuriensis* var.

subgenus *Armeniaca* (*P. armeniaca*).

A total of 186 putative alleles with a mean value of 12.4 per locus

Characters or bp (no.)

Prunus

Informative characters (no.)

Indels (no.) Substitutions (no.) Inversions (no.)

Percent variability

Phylogeny in classification

Notes The congeneric

Phylogenetic analysis

Analytical methods

**36**

Trees (no.) Strict consensus = 3 MPT

PIC *rpL*16 intron = 23 bp

No clear phylogenetic relationships were determined. The microsatellites are evolving too rapidly in North American plums to be truly useful at resolving species relationships

relationship of plums to peach and cherry allowed the successful use of these primers in section *Prunocerasus*. Microsatellites are evolving too rapidly to be truly useful at resolving species phylogeny

**Paper Bortiri et al. [31] Wen et al. [38]**

Morphology and molecular Molecular

MP, ML, and BI MP and BI


Phylogenetic analysis based on four single-copy cpDNA regions (*atp*B-*rbc*L, *mat*K, *rpl*16, and *trn*L-*trn*F) of Eurasian plums, *Prunus* section *Prunus*, confirmed this section to be monophyletic. Four well supported clades were reported: "Clade A" with *P. salicina*, *P. sogdiana*, and *P. ussuriensis*; "Clade B" with *P. cocomilia*; "Clade C" with *P. brigantina*, *P. ramburii*, and *P. spinosa*; and "Clade D" with subclade D1 *P. domestica-P. insititia*-*P. divaricata*-*P. ursine* and subclade D2 *P.*

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic…*

*DOI: http://dx.doi.org/10.5772/intechopen.91638*

Chavez et al. [39] identified genomic regions that provided the greatest number of characters and variability and improved the phylogenetic signal at the low level in *Prunus* section *Prunocerasus* relationships. The American and the Chickasaw clades were identified. An outgroup clade was comprised by *P. persica* and *P. fasciculata*. The results reported were similar to those reported by Mowrey and

Previous studies demonstrated the value of morphology, cytometry, nuclear DNA, and cpDNA as data for phylogenetic studies in *Prunus.* Most of the previous phylogenetic research used Mason's [21] and Rehder's [3] taxonomic classification. A complete summary of *Prunus* phylogenetic research is summarized in **Table 2**.

The subgenus *Prunus* section *Prunocerasus* (the North American plums) constitutes important genetic resources (gene pool) of unique traits such as tree architecture, chilling requirement, heat requirement, fruit development period, fruit size, fruit texture, disease and insect resistance, and adaptive changes to multiple environmental conditions, among others. These species could be used in the breeding of improved stone fruit cultivars in the future. The summary of the taxonomic and phylogenetic relationships presented in this chapter provides a base to understand the species relationships. In addition, it will help for the conservation and mainte-

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*cerasifera* [34].

Werner [23].

**4. Final remark**

**Author details**

Dario J. Chavez<sup>1</sup>

**39**

1 University of Georgia, USA

2 University of Florida, USA

nance of a broader germplasm base within *Prunus*.

\* and José X. Chaparro<sup>2</sup>

\*Address all correspondence to: dchavez@uga.edu

provided the original work is properly cited.

*PIC = potentially informative character.*

#### **Table 2.**

*Summary of* Prunus *phylogenetic studies.*

Endocarp and leaf morphometrics combined with AFLP markers were used to study the morphological and genetic variation of five European members of section *Prunus*: *P. cerasifera*, *P. cocomilia* Ten., *P. domestica*, *P. insititia* L., *P. spinosa* L., and *P. fruticans* [33]. Three clusters were reported: a first cluster *P. cerasifera-P. cocomilia*, a second *P. domestica-P. insititia*, and a third *P. spinosa* and *P. fruticans*.

*The North American Plums (*Prunus *Spp.): A Review of the Taxonomic… DOI: http://dx.doi.org/10.5772/intechopen.91638*

Phylogenetic analysis based on four single-copy cpDNA regions (*atp*B-*rbc*L, *mat*K, *rpl*16, and *trn*L-*trn*F) of Eurasian plums, *Prunus* section *Prunus*, confirmed this section to be monophyletic. Four well supported clades were reported: "Clade A" with *P. salicina*, *P. sogdiana*, and *P. ussuriensis*; "Clade B" with *P. cocomilia*; "Clade C" with *P. brigantina*, *P. ramburii*, and *P. spinosa*; and "Clade D" with subclade D1 *P. domestica-P. insititia*-*P. divaricata*-*P. ursine* and subclade D2 *P. cerasifera* [34].

Chavez et al. [39] identified genomic regions that provided the greatest number of characters and variability and improved the phylogenetic signal at the low level in *Prunus* section *Prunocerasus* relationships. The American and the Chickasaw clades were identified. An outgroup clade was comprised by *P. persica* and *P. fasciculata*. The results reported were similar to those reported by Mowrey and Werner [23].

Previous studies demonstrated the value of morphology, cytometry, nuclear DNA, and cpDNA as data for phylogenetic studies in *Prunus.* Most of the previous phylogenetic research used Mason's [21] and Rehder's [3] taxonomic classification. A complete summary of *Prunus* phylogenetic research is summarized in **Table 2**.

#### **4. Final remark**

The subgenus *Prunus* section *Prunocerasus* (the North American plums) constitutes important genetic resources (gene pool) of unique traits such as tree architecture, chilling requirement, heat requirement, fruit development period, fruit size, fruit texture, disease and insect resistance, and adaptive changes to multiple environmental conditions, among others. These species could be used in the breeding of improved stone fruit cultivars in the future. The summary of the taxonomic and phylogenetic relationships presented in this chapter provides a base to understand the species relationships. In addition, it will help for the conservation and maintenance of a broader germplasm base within *Prunus*.

#### **Author details**

Dario J. Chavez<sup>1</sup> \* and José X. Chaparro<sup>2</sup>


\*Address all correspondence to: dchavez@uga.edu

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Endocarp and leaf morphometrics combined with AFLP markers were used to study the morphological and genetic variation of five European members of section *Prunus*: *P. cerasifera*, *P. cocomilia* Ten., *P. domestica*, *P. insititia* L., *P. spinosa* L., and *P. fruticans* [33]. Three clusters were reported: a first cluster *P. cerasifera-P. cocomilia*, a second *P. domestica-P. insititia*, and a third *P. spinosa* and *P. fruticans*.

*PIC = total indels + nucleotide substitutions + inversions. Percent variability = PIC/characters or bp.*

**Paper Depypere et al. [33] Chavez et al. [39]**

Outgroups *P. fasciculata*, *P. persica*, and *P. pumila* Trees (no.) cpDNA sequences—MP = 13 MPT

SSRs (41), cpDNA (seven regions), nuclear genes (33 vernalization response genes, 16 tree architecture, and 3

A total of 8 species: *P. americana*, *P. angustifolia*, *P. hortulana*, *P. mexicana*, *P. munsoniana*, *P. geniculata*, *P. maritima, P.*

(L = 623, CI = 0.92, RI = 0.81, RC = 0.74) – ML = lnL = 5414.74. Nuclear genes – MP = 1 MPT (L = 2535, CI = 0.88, RI = 0.88, RC = 0.78) –

ML = lnL = 41509.34. Combined nuclear + cpDNA + ITS – MP = 2 MPT (L = 2732, CI = 0.88, RI = 0.88, RC = 0.77) – ML = lnL = 48496.34.

The American and the Chickasaw clades were identified. An outgroup clade was comprised by *P. persica* and *P. fasciculata*

Identified multiple gene regions that provided the greatest number of characters, variability, and improved phylogenetic signal at the species level in

*Prunus* section *Prunocerasus*

Combined data set = 27,623 bp

isozymes), and ITS

*umbellata*

1594

Leaf and endocarp morphometrics and

A total of 82 accessions/5 species: *P. cerasifera*, *P. domestica*, *P. insititia*, *P. spinosa,* and *P. fruticans*,

PCoA and AFLP of three distinct clusters. A first cluster consists of all *P. cerasifera* samples and the sole *P. cocomilia*. A second cluster includes all individuals of *P. domestica* and *P. insititia*. A third cluster comprises all *P. spinosa* and *P. fruticans*

samples

*PIC = potentially informative character.*

*Summary of* Prunus *phylogenetic studies.*

Notes Low number of *Prunus* species for sampling

AFLP primers

Metrics (analysis)

Prunus

Taxa (no.)/ subgenus (sect.)/genus

Characters or bp (no.)

Informative characters (no.)

Indels (no.) Substitutions (no.) Inversions (no.) PIC Percent variability Phylogeny in classification

*z*

**38**

**Table 2.**
