**2. Classification of the D diploid species, distribution, and dissemination**

The country of Mexico, besides being a part of the center of origin/diversity of *G. hirsutum,* also harbored 11 out of the 13 formally reported D species [3,7] and several non-described taxa of the New World diploid *Gossypium* species (one non-described taxon US-72,) [8-10]. The species of the *Houzingenia* subgenus are classified into six subsections: subsection *Houzingenia* Fryxell [*G. thurberi* Todaro (D1) and *G. trilobum* (Mociño & Sessé ex DC.) Skovsted (D8)]; subsection *Integrifolia* Todaro [*G. davidsonii* Kellogg (D3-d) and *G. klotzschianum* Andersson (D3-k)]; subsec‐ tion *Caducibracteolata* Mauer [*G*. *armourianum* Kearney (D2-1), *G*. *harknessii* Brandegee (D2-2), and *G*. *turneri* Fryxell (D10)]; subsection *Erioxylum* Rose & Standley [*G. aridum* (D4)*, G. lobatum* (D7)*, G. laxum* (D9)*,* and *G. schwendimanii* Fryx. & Koch (D11)]; subsection *Selera* (Ulbrich) Fryxell [*G*. *gossypioides* (D6)], and subsection *Austroamericana* Fryxell [*G. raimondii* Ulbrich (D5)] [3,4,7]. Eleven of the 13 species of the subgenus *Houzingenia* are distributed in Mexico and extend northward into Arizona (Fig. 1). The other two D species have disjointed distributions; *G. raimondii* is endemic to Peru, while *G. klotzschianum* is found in the Galápagos Islands. The species of the D genome are not well known and utilized in public and private breeding programs around the world. Additional information about morphological characteristics and distribution of the species can be found in Fryxell monograph [12] and several other publica‐ tions [8-9]. A supplemental information about recent collections [8-9] can be found at the USDA-ARS, SPA, CSRL, Plant Stress and Germplasm Development website (http:// www.lbk.ars.usda.gov/psgd/index-cotton.aspx). Also, the Mexican Instituto Nacional de Investigaciones Forestales Agricolas y Pecuarias (INIFAP), Iguala Gro. Mex. nursery has provided us with the opportunity to further study some of these species *ex situ*. Table 1 provides information on 12 of the species during their *ex situ* preservation at the Iguala nursery in Mexico. Data from *G. klotzschianum* is missing from this table. Species planted at the nursery flower from September to January, while *in situ*, some of the populations from these species flower through March-April..


populations in the states of Colima, Guerrero, and Oaxaca mature their capsules in February and March. Well-documented populations of collected *G. aridum* have now been made from several regions representing different non-described taxa and ecotypes [9]. These collections will continue to allow for *ex situ* preservation, maintenance and evaluation. This will also allow

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**Figure 2.** Habitat, trees, flower, capsule, and leaves of collected accessions of the *G. aridum* species.

be threatened (Fig. 1).

For the most part, populations of *G. aridum* occur as a part of the native vegetation in deciduous woodlands. Different non-described taxa and ecotypes appear to thrive in areas where the woodland is disturbed, particularly along road banks where the canopy is opened. In the niches where they occur, some of these populations are usually found in abundance, although these locations may be separated by many kilometers. This species, as presently circumscribed, is very diverse (non-described taxa/ecotypes) and some of these populations do not appear to

*Gossypium armourianum***(D2)** is distributed from Baja California to the Gulf of California on the San Marcos Island (Fig. 1). This species can be described as a compact branched shrub of around one m tall. The species for the most part contains ovate leavesyellow flowers with withe

common-garden comparisons of all populations.

**Table 1.** Averages of flowers and seed characteristics taken on some of the *Gossypium* species of the D genome established in the permanent nursery at Iguala, Guerrero Mexico.

*Gossypium aridum***(D4)**, as formally reported, is the most widely distributed wild *Gossypium* in Mexico [5,9]. The distribution of this species, non-described taxa (one non-described taxon US-72, [8-11]), and described ecotypes [8-9,11] of the New World extends from the northern state of Sinaloa to the southern state of Oaxaca (Fig. 1). The species and taxa/ecotypes can be described as medium to large trees from five to 18 m tall or larger. As expected from its wide range, this *Gossypium* species occupies a number of habitat niches (http:// www.lbk.ars.usda.gov/psgd/index-cotton.aspx). Comparisons among specimens of on-site observations indicate extensive differences in leaf size, vestiture of the leaves, morphology in the lysigenous glands on the capsules, and period of flowering. Morphologically, the leaves of the ecotype from Oaxaca are the largest of the species, with a relatively dense but fine indumentum. Several populations of *G. aridum* that appear to be very similar in morphology are distributed along the coastal foothills of Jalisco, Colima, Guerrero, and possibly Michoacán. Figure 2 presents an accessions of a population collected from recent exploration/collection trips [8-9]. The elevation of these populations range from <60 m up to >1000 m. Generally, these populations have almost no leaf trichomes, and small mature capsules (Table 1). Also, flowering in the states of Sinaloa, Nayarit and Jalisco is delayed until March and April in these types, and their capsules do not mature until late April-May (Fig. 2). While the Coastal populations in the states of Colima, Guerrero, and Oaxaca mature their capsules in February and March. Well-documented populations of collected *G. aridum* have now been made from several regions representing different non-described taxa and ecotypes [9]. These collections will continue to allow for *ex situ* preservation, maintenance and evaluation. This will also allow common-garden comparisons of all populations.

**Species Genome**

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**Petal color**

*G. trilobum* D8 Yellow Yellow Yellow

established in the permanent nursery at Iguala, Guerrero Mexico.

**Filament color**

*G. aridum* D4 Cherry Purple Purple Cordate 14 7.3 1.7 *G. armourianum* D2 Yellow White Cherry Ovate 13 6.0 1.7 *G. davidsonii* D3-d Yellow Yellow Yellow Cordate 14 4.8 1.8 *G. gossypioides* D6 Cherry Purple Purple Palmate 9 5.0 1.8 *G. harknessii* D2-2 Yellow Amarlla Yellow Cordate 7 6.6 4.3 *G. laxum* D9 Cherry Purple Purple Lobed 6 8.8 1.6 *G. lobatum* D7 Cherry Purple Purple Lobed 8 10 1.8 *G. schwendimanii* D11 Cherry Purple Purple Cordate 7 10 2.5 *G. raimondii* D5 Yellow Purple Purple Cordate 12 7.0 3.6 *G. thurberi* D1 Yellow White Yellow Palmate 14 3.3 1.6

*G. turneri* D10 Yellow Yellow Yellow Cordate 10 3.8 1.8

**Table 1.** Averages of flowers and seed characteristics taken on some of the *Gossypium* species of the D genome

*Gossypium aridum***(D4)**, as formally reported, is the most widely distributed wild *Gossypium* in Mexico [5,9]. The distribution of this species, non-described taxa (one non-described taxon US-72, [8-11]), and described ecotypes [8-9,11] of the New World extends from the northern state of Sinaloa to the southern state of Oaxaca (Fig. 1). The species and taxa/ecotypes can be described as medium to large trees from five to 18 m tall or larger. As expected from its wide range, this *Gossypium* species occupies a number of habitat niches (http:// www.lbk.ars.usda.gov/psgd/index-cotton.aspx). Comparisons among specimens of on-site observations indicate extensive differences in leaf size, vestiture of the leaves, morphology in the lysigenous glands on the capsules, and period of flowering. Morphologically, the leaves of the ecotype from Oaxaca are the largest of the species, with a relatively dense but fine indumentum. Several populations of *G. aridum* that appear to be very similar in morphology are distributed along the coastal foothills of Jalisco, Colima, Guerrero, and possibly Michoacán. Figure 2 presents an accessions of a population collected from recent exploration/collection trips [8-9]. The elevation of these populations range from <60 m up to >1000 m. Generally, these populations have almost no leaf trichomes, and small mature capsules (Table 1). Also, flowering in the states of Sinaloa, Nayarit and Jalisco is delayed until March and April in these types, and their capsules do not mature until late April-May (Fig. 2). While the Coastal

**Anther color**

**Leaf shape**

Lobed - Palmate **Number of seed per capsule**

**Seed Size length mm**

12 4.0 1.2

**Seed width mm**

**Figure 2.** Habitat, trees, flower, capsule, and leaves of collected accessions of the *G. aridum* species.

For the most part, populations of *G. aridum* occur as a part of the native vegetation in deciduous woodlands. Different non-described taxa and ecotypes appear to thrive in areas where the woodland is disturbed, particularly along road banks where the canopy is opened. In the niches where they occur, some of these populations are usually found in abundance, although these locations may be separated by many kilometers. This species, as presently circumscribed, is very diverse (non-described taxa/ecotypes) and some of these populations do not appear to be threatened (Fig. 1).

*Gossypium armourianum***(D2)** is distributed from Baja California to the Gulf of California on the San Marcos Island (Fig. 1). This species can be described as a compact branched shrub of around one m tall. The species for the most part contains ovate leavesyellow flowers with withe filaments and cherry anthers. The seeds are contained in a capsule with three to four cells, and seeds averaging 6.0 x 1.7 mm with brownish tightly compressed fibers (Table 1; [12]).

this species as *G. raimondii* possess a unique petal mutation called reverse petal spot (pigment is present on adaxial and abaxial petal surfaces). *G. gossypioides* has been reported with cryptic repeated genomic recombination during speciation, with conflicting morpho‐ logical, cytogenetic, and molecular evidence of its phylogenetic affinity to other New World cottons [13]. Figure 4 presents trees and mature capsules encountered at the natural habitat of this species. The seeds are contained in a capsule with three cells and seeds averaging

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**Figure 4.** One year accession of the species *G. gossypioides* which was maintained at the Iguala Guerrero Mex. nursery

*Gossypium harknessii***(D2-2)** is adapted to the desert environments of Baja California in the Cape region and adjacent islands. This species is described as a shrub of around three m tall and for the most part with cordate leaves. Plants present flowers with yellow colored petals, filaments, and anthers. The seeds are contained in a capsule commonly with three-to four cells and seeds

*Gossypium klotzschianum***(D3-k)** is one of the two species with disjointed distribution (not found in the country of Mexico) and is endemic to the Galápagos Islands. This species is described as a shrub up to four m tall and for the most part with petiolate-cordate leaves. Plants maintained at the Iguala nursery present flowers with yellow petals, filaments, and anthers.

averaging 6.6 x 4.3 mm with grayish sparse compressed fibers (Table 1; [12]).

with a flower, also, trees and mature capsules encountered at its natural habitat.

5.0 x 1.8 mm with grayish sparse compressed fibers (Table 1; [12]).

**Figure 3.** A two-year shrub of the species of *G. davidsonii*.

*Gossypium davidsonii***(D3-d)** is adapted to the desert environments of the southern Baja California peninsula and across the Gulf of California in the state of Sonora. This species is described as a branched shrub of one to two m tall and for the most part with cordate leaves. Figure 3 presents one of the accessions maintained at the Iguala nursery with cordate leaves. This species has flowers with yellow colored petals, filaments, and anthers. The seeds are contained in a capsule commonly with four cells and seeds averaging 4.8 x 1.8 mm with sparse com‐ pressed fibers (Table 1; [12]).

*Gossypium gossypioides***(D6)** is distributed in the central part of the state of Oaxaca and is adapted to a higher altitude than any other arborescent D *Gossypium* species, >1000 m. This species has been encountered only in the state of Oaxaca. It has been hypothesized that the distribution of *G. gossypioides* may be strongly influenced by elevation. One aspect of *G. gossypioides* that was recently reported is its deciduous habit as a drought escaping mechanism [8]. This species, like the other arborescent *Gossypium* species in the section *Erioxylum,* occurs in dry deciduous woodlands of Oaxaca and defoliates with the onset of the dry season. However, unlike the species of subsection *Erioxylum,* it flowers and fruits near the end of the wet season before defoliating. Fryxell [5] was unaware of the decidu‐ ous nature of the foliage similar to the other arborescent species of Mexico, which defoliat‐ ed as a mechanism to escape drought. This species is comprised of small trees from three to seven m tall. Figure 4 presents one of the accessions (one year old) maintained at the Iguala nursery with flowers with light cherry color, and purple filaments and anthers. Also,

this species as *G. raimondii* possess a unique petal mutation called reverse petal spot (pigment is present on adaxial and abaxial petal surfaces). *G. gossypioides* has been reported with cryptic repeated genomic recombination during speciation, with conflicting morpho‐ logical, cytogenetic, and molecular evidence of its phylogenetic affinity to other New World cottons [13]. Figure 4 presents trees and mature capsules encountered at the natural habitat of this species. The seeds are contained in a capsule with three cells and seeds averaging 5.0 x 1.8 mm with grayish sparse compressed fibers (Table 1; [12]).

filaments and cherry anthers. The seeds are contained in a capsule with three to four cells, and

*Gossypium davidsonii***(D3-d)** is adapted to the desert environments of the southern Baja California peninsula and across the Gulf of California in the state of Sonora. This species is described as a branched shrub of one to two m tall and for the most part with cordate leaves. Figure 3 presents one of the accessions maintained at the Iguala nursery with cordate leaves. This species has flowers with yellow colored petals, filaments, and anthers. The seeds are contained in a capsule commonly with four cells and seeds averaging 4.8 x 1.8 mm with sparse com‐

*Gossypium gossypioides***(D6)** is distributed in the central part of the state of Oaxaca and is adapted to a higher altitude than any other arborescent D *Gossypium* species, >1000 m. This species has been encountered only in the state of Oaxaca. It has been hypothesized that the distribution of *G. gossypioides* may be strongly influenced by elevation. One aspect of *G. gossypioides* that was recently reported is its deciduous habit as a drought escaping mechanism [8]. This species, like the other arborescent *Gossypium* species in the section *Erioxylum,* occurs in dry deciduous woodlands of Oaxaca and defoliates with the onset of the dry season. However, unlike the species of subsection *Erioxylum,* it flowers and fruits near the end of the wet season before defoliating. Fryxell [5] was unaware of the decidu‐ ous nature of the foliage similar to the other arborescent species of Mexico, which defoliat‐ ed as a mechanism to escape drought. This species is comprised of small trees from three to seven m tall. Figure 4 presents one of the accessions (one year old) maintained at the Iguala nursery with flowers with light cherry color, and purple filaments and anthers. Also,

seeds averaging 6.0 x 1.7 mm with brownish tightly compressed fibers (Table 1; [12]).

**Figure 3.** A two-year shrub of the species of *G. davidsonii*.

pressed fibers (Table 1; [12]).

208 World Cotton Germplasm Resources

**Figure 4.** One year accession of the species *G. gossypioides* which was maintained at the Iguala Guerrero Mex. nursery with a flower, also, trees and mature capsules encountered at its natural habitat.

*Gossypium harknessii***(D2-2)** is adapted to the desert environments of Baja California in the Cape region and adjacent islands. This species is described as a shrub of around three m tall and for the most part with cordate leaves. Plants present flowers with yellow colored petals, filaments, and anthers. The seeds are contained in a capsule commonly with three-to four cells and seeds averaging 6.6 x 4.3 mm with grayish sparse compressed fibers (Table 1; [12]).

*Gossypium klotzschianum***(D3-k)** is one of the two species with disjointed distribution (not found in the country of Mexico) and is endemic to the Galápagos Islands. This species is described as a shrub up to four m tall and for the most part with petiolate-cordate leaves. Plants maintained at the Iguala nursery present flowers with yellow petals, filaments, and anthers. The seeds are contained in a capsule commonly with four cells, ciliate on inner suture margins, and seeds averaging 5.0 x 2.5 mm with sparse inconspicuous fibers [12].

*Gossypium schwendimanii***(D11)** is the most recently described *Gossypium* species of the D genome from Mexico [3,12]. This species was encountered for the first time at the Guerrero-Michoacán border near Infiernillo where a population of *G. aridum* was located only 2 km from "typical" *G. schwendimanii*. Collected accessions from this location showed some morphological features similar to *G. aridum* that suggested some introgression between the two species. Recently, *G. schwendimanii* [9] was collected from an area about 20 km south of *G. lobatum*. Seeds were collected from two additional populations of *G. schwendimanii* from the hills above the west side of Presa Infiernillo. Little morphological diversity was evident among the populations. The full natural distribution or native range of *G. schwendimanii* is unclear because of the limited information available on the species. One factor that has an impact on its genetic identity is its apparent sympatry with *G. aridum* and *G. lobatum* over parts of its range. It is adapted to altitude ranging from 200 to 400 m. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and produces fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. The seeds are contained in a capsule with three-or four-cells and seed averaging 10.0 x 2.5 mm with densely pubescent fibers (Table

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*Gossypium thurberi***(D1)** is distributed from the state of Arizona, U.S.A to the state of Sonora, Mexico. This species can be described as a small tree or shrub of around 3 m tall. The species for the most part contains palmate leaves with flowers from white to yellow color, white filaments, and yellow anthers. The seeds are contained in a capsule with three-cells and seeds

*Gossypium trilobum***(D8)** is generally limited to moderately high elevations (1200 m) in western Mexico. This species belongs to section *Houzingenia* and is a sister species to *G. thurberi*, the most northerly (Sonora-Mex to Arizona-U.S.) distributed species of the *Gossypium.* Even though Fryxell [5] indicated that it was widely distributed from the state of Sinoloa to the state of Morelos, few if any collections have been made in the last 30 years in any of these locations. Based on the results of a survey made by Ulloa et al [8-9] special mention should be made of *G. trilobum*. In 2002-2004, sites were visited where herbarium specimens were collected in the past. In each of five widely separated locations represent‐ ed by herbarium (MEXU) collections (sites in N and W México, Jalisco, Michoacán, and Morelos), *G. trilobum* plants or populations were unable to be located. Although the status of *G. trilobum* in remote areas is unknown, the results from the survey by Ulloa et al [8-9] confirmed that the distribution of this species has been severely eroded by agricultural and human-population pressures. For the most part, the habitat of this species has been replaced by intense and extensive agricultural production of guava (*Psidium* spp.) in the State of Michoacan, Mexico. At this point, *G. trilobum* species is almost extinct or is becoming extinct in the wild. This species can be described as a small tree or shrub of around 4 m tall. The species for the most part contains lobed-palmate leaves, and yellow flowers, filaments and anthers. The seeds are contained in a capsule with three-cells and seeds averaging 4.0 x 1.2

averaging 3.3 x 1.6 mm with blackish color and no fibers (Table 1; [12]).

mm with blackish color and compressed pubescence (Table 1; [12]).

1; [9]).

*Gossypium laxum***(D9)** is reported to be located in the Cañon del Zopilote in the central state of Guerrero, and, more recently, it was reported to be found in the state of Michoacan along the road between Huetamo and Nuevo Churumuco. The full range of *G. laxum* is yet to be determined, but it probably extends many kilometers along the Rio Balsas watershed east and west of Cañon del Zopilote. This taxon does well in areas of open sunlight, such as road cuts, like other members of subsection *Erioxylum*. However, it can also be found as part of natural deciduous woodland vegetation. Morphological diversity is not extensive among the acces‐ sions that have been collected so far. The collected accession (US-98, D9-6-M, [9]) significantly extended the range of this species to the west. It is adapted to altitudes ranging from 200 to 900 m. Because some habitat sites of this species have generally been found not suitable for agriculture, *G. laxum* may be able to survive Mexico's demographic changes and does not seem to be threatened at present. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and produces fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. US-98 accession presented flowers similar to *G. lobatum*. The seeds are contained in a capsule with three-to five-cells and seeds averaging 8.8 x 1.6 mm with densely pubescent fibers (Table 1; [12]).

*Gossypium lobatum* (D7) is adapted to the environment of the central state of Michoacan. The collected accession (US-112, D7-10-M, [9]) extended the range of this species to the west of the state. The distribution of this taxon is probably throughout the Rio Tepalcatepec watershed with an eastern extension along the Rio Balsas watershed. *G. lobatum* has unique features such as its distichous leaf insertion and tomentose calyces with prominent lobes, the characteristic from which its name is derived. While all accessions had distichous leaves, the calyces of the western accession-populations were less hairy and the lobes less prominent. It is unknown how much suitable habitat has already been destroyed. Overall the species does not appear to be threatened at present. It is adapted to altitude ranging from 200 to 400 m. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. The seeds are contained in a capsule with three-cells and seeds averaging 10.0 x 1.8 mm with densely pubescent fibers (Table 1; [2]).

*Gossypium raimondii***(D5)** is the other of the two D species that has disjointed distribution and is endemic to Peru. This species was originally described as a shrub two to three m tall. However, accessions planted at the Iguala nursery from seed provided by the USDA-ARS Cotton Germplasm Collection, College Station TX were able to produce shrub like trees up to 10 m tall. For the most part, accessions at the Iguala nursery present large cordate leaves, flowers with yellow petals, and purple filaments and anthers. The seeds are contained in a capsule commonly with four-cells, narrowly ovoid, and seeds averaging 7.0 x 3.6 mm with densely pubescent fibers [12]. *G. raimondii* is considered the closest living ancestor relative of the allotetraploid cottons (Dt subgenome) [4,12].

*Gossypium schwendimanii***(D11)** is the most recently described *Gossypium* species of the D genome from Mexico [3,12]. This species was encountered for the first time at the Guerrero-Michoacán border near Infiernillo where a population of *G. aridum* was located only 2 km from "typical" *G. schwendimanii*. Collected accessions from this location showed some morphological features similar to *G. aridum* that suggested some introgression between the two species. Recently, *G. schwendimanii* [9] was collected from an area about 20 km south of *G. lobatum*. Seeds were collected from two additional populations of *G. schwendimanii* from the hills above the west side of Presa Infiernillo. Little morphological diversity was evident among the populations. The full natural distribution or native range of *G. schwendimanii* is unclear because of the limited information available on the species. One factor that has an impact on its genetic identity is its apparent sympatry with *G. aridum* and *G. lobatum* over parts of its range. It is adapted to altitude ranging from 200 to 400 m. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and produces fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. The seeds are contained in a capsule with three-or four-cells and seed averaging 10.0 x 2.5 mm with densely pubescent fibers (Table 1; [9]).

The seeds are contained in a capsule commonly with four cells, ciliate on inner suture margins,

*Gossypium laxum***(D9)** is reported to be located in the Cañon del Zopilote in the central state of Guerrero, and, more recently, it was reported to be found in the state of Michoacan along the road between Huetamo and Nuevo Churumuco. The full range of *G. laxum* is yet to be determined, but it probably extends many kilometers along the Rio Balsas watershed east and west of Cañon del Zopilote. This taxon does well in areas of open sunlight, such as road cuts, like other members of subsection *Erioxylum*. However, it can also be found as part of natural deciduous woodland vegetation. Morphological diversity is not extensive among the acces‐ sions that have been collected so far. The collected accession (US-98, D9-6-M, [9]) significantly extended the range of this species to the west. It is adapted to altitudes ranging from 200 to 900 m. Because some habitat sites of this species have generally been found not suitable for agriculture, *G. laxum* may be able to survive Mexico's demographic changes and does not seem to be threatened at present. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and produces fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. US-98 accession presented flowers similar to *G. lobatum*. The seeds are contained in a capsule with three-to five-cells and seeds

*Gossypium lobatum* (D7) is adapted to the environment of the central state of Michoacan. The collected accession (US-112, D7-10-M, [9]) extended the range of this species to the west of the state. The distribution of this taxon is probably throughout the Rio Tepalcatepec watershed with an eastern extension along the Rio Balsas watershed. *G. lobatum* has unique features such as its distichous leaf insertion and tomentose calyces with prominent lobes, the characteristic from which its name is derived. While all accessions had distichous leaves, the calyces of the western accession-populations were less hairy and the lobes less prominent. It is unknown how much suitable habitat has already been destroyed. Overall the species does not appear to be threatened at present. It is adapted to altitude ranging from 200 to 400 m. This species is another arborescent *Gossypium* species of the subsection *Erioxylum* and comprises trees up to 10 m tall *in situ*. It flowers and fruits near the end of the wet season before defoliating. Plants of these populations present flowers with light cherry color, and purple filaments and anthers. The seeds are contained in a capsule with three-cells and seeds averaging 10.0 x 1.8 mm with

*Gossypium raimondii***(D5)** is the other of the two D species that has disjointed distribution and is endemic to Peru. This species was originally described as a shrub two to three m tall. However, accessions planted at the Iguala nursery from seed provided by the USDA-ARS Cotton Germplasm Collection, College Station TX were able to produce shrub like trees up to 10 m tall. For the most part, accessions at the Iguala nursery present large cordate leaves, flowers with yellow petals, and purple filaments and anthers. The seeds are contained in a capsule commonly with four-cells, narrowly ovoid, and seeds averaging 7.0 x 3.6 mm with densely pubescent fibers [12]. *G. raimondii* is considered the closest living ancestor relative of

and seeds averaging 5.0 x 2.5 mm with sparse inconspicuous fibers [12].

210 World Cotton Germplasm Resources

averaging 8.8 x 1.6 mm with densely pubescent fibers (Table 1; [12]).

densely pubescent fibers (Table 1; [2]).

the allotetraploid cottons (Dt subgenome) [4,12].

*Gossypium thurberi***(D1)** is distributed from the state of Arizona, U.S.A to the state of Sonora, Mexico. This species can be described as a small tree or shrub of around 3 m tall. The species for the most part contains palmate leaves with flowers from white to yellow color, white filaments, and yellow anthers. The seeds are contained in a capsule with three-cells and seeds averaging 3.3 x 1.6 mm with blackish color and no fibers (Table 1; [12]).

*Gossypium trilobum***(D8)** is generally limited to moderately high elevations (1200 m) in western Mexico. This species belongs to section *Houzingenia* and is a sister species to *G. thurberi*, the most northerly (Sonora-Mex to Arizona-U.S.) distributed species of the *Gossypium.* Even though Fryxell [5] indicated that it was widely distributed from the state of Sinoloa to the state of Morelos, few if any collections have been made in the last 30 years in any of these locations. Based on the results of a survey made by Ulloa et al [8-9] special mention should be made of *G. trilobum*. In 2002-2004, sites were visited where herbarium specimens were collected in the past. In each of five widely separated locations represent‐ ed by herbarium (MEXU) collections (sites in N and W México, Jalisco, Michoacán, and Morelos), *G. trilobum* plants or populations were unable to be located. Although the status of *G. trilobum* in remote areas is unknown, the results from the survey by Ulloa et al [8-9] confirmed that the distribution of this species has been severely eroded by agricultural and human-population pressures. For the most part, the habitat of this species has been replaced by intense and extensive agricultural production of guava (*Psidium* spp.) in the State of Michoacan, Mexico. At this point, *G. trilobum* species is almost extinct or is becoming extinct in the wild. This species can be described as a small tree or shrub of around 4 m tall. The species for the most part contains lobed-palmate leaves, and yellow flowers, filaments and anthers. The seeds are contained in a capsule with three-cells and seeds averaging 4.0 x 1.2 mm with blackish color and compressed pubescence (Table 1; [12]).

**3. Collections/explorations and unclassified taxa**

return to Russia (Q. Obispo, personal communication; [8]).

without rain.

The gene pool of Upland/Acala *G. hirsutum* from the country of Mexico derived one of the primary sources for improvement of most of the Acala and Upland cotton growing in the world today. In addition, another cotton genetic resource of this country is the 11 formally reported D diploid *Gossypium* species and several unclassified taxa [8-11] of the Western Hemisphere. Mexico and its boundaries are the center of diversity of these endemic species. Some of these species and their genomes (US-72, D4, D7, D9, D10, and D11) with arborescent or shrub growth habits express unique flowering and fruiting habits (following defoliation in the dry season) and salt and drought resistance mechanisms that allow them to survive extended periods

The Diploid D Genome Cottons (*Gossypium* spp.) of the New World

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Because of the importance of the gene pool of *G. hirsutum* from Mexico, the collection/ exploration trips of the D diploid species have been difficult to execute and document. Two of the greatest explorers and taxonomists of the *Gossypium* genus, and especially species from the country of Mexico, were Drs. Fryxell and Stewart. P.A. Fryxell made several collectionexpeditions from 1968 to 1975 in the country, providing a larger number of specimens to several Herbariums (Herbarium Nacional de Mexico-MEXU and Herbarium Instituto de Ecologia A.C. Mexico-XAL) with clear and precise descriptions of habitat and location of collected accessions [5]. He also made the most recent taxonomic classification of *Gossypium* species [7]. A. E. Percival, J. M. Stewart (USDA), A. Hernandez and F. de Leon (INIFAP) made several collection-expeditions in 1984 throughout the states of the Yucatan Peninsula and in parts of the states of Tamaulipas, Veracruz, Tabasco, Oaxaca and Chiapas. Also, A. E. Percival (USDA-ARS), J. M. Stewart (Univ. of Arkansas), E.A. Garcia, and L. Peréz (INIFAP, Mexico) made additional collection-expeditions in 1990 in the state of Baja California Sur and parts of the states of Sonora and Sinaloa. As a result of their early efforts, a number of *Gossypium* accessions of the subgenus *Houzingenia* from various parts of Mexico were deposited in the USDA-ARS Cotton Germplasm Collection College Station, TX, USA. Also, during the 1980s, Dr. Lemeshev of the Academy of Science of Russia established a *Gossypium* nursery in Iguala City, state of Guerrero in the country of Mexico. Also, some or all of these species are catalogued in the germplasm collection of the Vavilov Institute in St. Petersburg and in several collections of Former Soviet Union countries (e.g., Uzbekistan) based on several collection-expeditions by the Universidad Autónoma de Guerrero Mexico and the Academy of Science of Russia in the states of Veracruz, Tabasco, Campeche, Yucatán, Chiapas, Guerrero, Oaxaca, Michoacán, Morelos, Colima, Sinaloa, Sonora and Baja California Sur between 1989 and 1993 by F. Talipov, C. Cataláio, F. Salgado and M. Bahena. This nursery was abandoned upon Dr. Lemeshev's

Until recently no national resources were dedicated to the preservation of this natural treasure [8-9]. In 2002-2006, the United States Department of Agriculture – Agriculture Research Service (USDA-ARS) and the Mexican Instituto Nacional de Investigaciónes Forestales Agricolas y Pecuarias (INIFAP) sponsored joint *Gossypium* germplasm collection trips by U.S. and Mexican cotton scientists. As a result of these efforts, a significant number of *Gossypium* accessions of the subgenus *Houzingenia* from various parts of Mexico were collected (Table 2). Collected

**Figure 5.** Shrubs of *G. turneri* in their natural habitat showing green vegetation after extended drought.

*Gossypium turneri***(D10)** is adapted to the coast of the state of Sonora Mpio. of Guaymas and primarily associated with soils of weathered igneous concentration (Fig. 1). On a long-term basis, *G. turneri* is well adapted to the sea-shore environments and sea level altitude in which it occurs. Based on a recent exploration (J.M. Stewart and M. Ulloa, 2004 expedition), the species has salt and drought resistance mechanisms that allow it to survive extended periods without rain. During this trip, the first *G. turneri* bush encountered was actually in the yard/sea-cliff. Although the species had a very small yield of seed the year when it was encountered because of drought, no evidence was seen of plants that died from the lack of water. Like most other *Gossypium*, in those areas where the species occurs, the plants are quite numerous. Unless unforeseen expansion of the resort industry occurs along the coastal region north of La Manga, the species habitat, in general, probably will not undergo rapid degradation. If resort con‐ struction should occur on the sea cliffs and adjoining valleys, then the species most likely would be lost in the wild. This species can be described as a shrub of around 1 m tall. Figure 5 presents shrubs in their natural habitat still showing green vegetation after extended drought. The species for the most part contains cordate leaves with yellow flowers, filaments and anthers. The seeds are contained in a capsule with three-to five-cells and seeds averaging 3.8 x 1.8 mm with blackish color and compressed pubescence (Table 1; [12]).
