Discussion

Previous studies of genetic diversity within the M. acuminata complex have suggested geographic distribution as a determining factor (Cheesman 1947, 1948; Simmonds 1956; De Langhe et al. 2000; Perrier et al. 2009, 2011; Jenny et al. 2024). However, delimitation of wild Musa species is difficult. The herbaceous habit and large dimensions of the leaves and inflorescences of bananas make the preservation of herbarium specimens challenging (e.g., Simmonds 1956; De Langhe et al. 2000). Many specimens include only immature fruits, which are insufficient for correct identification. Published records often provide insufficient descriptions that focus mainly on pseudostem and inflorescence characteristics, rendering identification problematic. This study aims to address these limitations through repeated field campaigns in Thailand, providing detailed documentation of morphological and genetic variation. All voucher specimens were prepared from plants occurring in the wild and were georeferenced and photographed. The colors were described using a standard color chart (IPGRI-INIBAP/CIRAD 1996). Representatives of the selected taxonomic entities were sketched in the field and later inked for the final plates.

Taxonomic status of the M. acuminata complex

Segregation of the M. acuminata complex in Thailand into species and subspecies corroborated previous taxonomic treatments (Simmonds 1956; De Langhe et al. 2000; Wong et al. 2001; Perrier et al. 2009; Rouard et al. 2018). Dendrograms generated from morphological and distributional data (Fig. 6) strongly supported the recognition of M. acuminata as a distinct species, consistent with conventional classifications (Cheesman 1948; Simmonds 1956; Nasution 1991; Wong et al. 2001; Inta et al. 2023). The extensive sampling of M. acuminata across Thailand provides substantial evidence supporting the use of subspecific ranks within the complex, a view contrasting with Nasution’s (1991) classification of all M. acuminata variations in Indonesia as varieties. Nasution erected 15 varieties to accommodate the subspecific variation, including nine new combinations encompassing acuminata, malaccensis, and microcarpa, but did not provide justification for these taxonomic decisions. The findings align more closely with Simmonds’ (1956: 469) assertion that the various forms of M. acuminata represent “distinct geographico-morphological units.” Indeed, the geographically defined distributions of the M. acuminata infraspecific taxa observed in this study are congruent with the results of phenetic analyses (Perrier et al. 2009).

Moreover, the status of the four subspecies—siamea, malaccensis, truncata, and the newly described kraburiensis—is well supported by the morphological analysis (Fig. 6). The separation of the four subspecies, as shown in the following key, was determined mainly by leaf base shape, rachis position, bud imbrication, and the color of male bracts. Meanwhile, several characters previously used by banana researchers were found to be highly variable among different populations within the subspecies. These ambiguous characters included blotches on the leaves of young suckers, pseudostem pigmentation, and waxiness of the leaf sheaths. In addition, the shapes of the free tepals used by Nasution (1991) to discriminate var. malaccensis and var. microcarpa were not helpful. Nasution described var. malaccensis as having a rounded, acuminate free tepal and var. microcarpa as having an obovate, acute free tepal. Previous work (Inta et al. 2023) examined floral morphological evolution in Musa and suggested that tepal morphology is uniform across M. acuminata subspecies, with the tepals of all subspecies exhibiting an elliptic shape and an acuminate apex.

On the identity of subspecies siamea and burmannica

Although M. acuminata subsp. siamea and subsp. burmannica (mentioned as the ‘Annam’ and ‘Tavoy’ forms, respectively, by Cheesman 1948) were traditionally described as having similar obtuse, imbricate, and red-purple male-phase inflorescences, they were previously separated based on waxiness and pigmentation of the pseudostems, bud shapes, bunch position and compactness, and the length of the fruit pedicel and apex (Cheesman 1948; Simmonds 1956; De Langhe and Devreux 1960). The collection lacked accessions exhibiting the complete suite of characteristic traits of Simmonds’ subsp. siamea (waxy pseudostem, subhorizontal and compact bunch, tepals often with yellow tips, and polygonal-round fruit cross section) or the corresponding suite of traits of Simmonds’ subsp. burmannica (non-waxy pseudostem, pendant and lax bunch, and angular fruit cross section).

Further confusion arises from the use of fruit pedicel and apex lengths, which different authors have ascribed to the subspecies. Cheesman (1948: 27) described the “Tavoy form” (M. acuminata subsp. burmannica sensu Simmonds) as having “the pedicel very short and not very distinct, acumen approximately 0.5 cm long.” Conversely, he described the “Annam form” (M. acuminata subsp. siamea sensu Simmonds) as having “a short (0.5 cm) but quite distinct pedicel and a well-marked acumen 0.5 cm long.” However, De Langhe and Devreux (1960) presented contrasting data in their comparative morphological table. They stated that subsp. burmannica has a long fruit pedicel (1 cm) and a long apex (1 cm or longer), whereas subsp. siamea has a shorter fruit pedicel and apex (0.5 cm).

Jenny et al. (2024) also reported that the morphological traits they examined were insufficient to definitively classify specimens within the subsp. siamea/burmannica complex because of the morphological similarity of these specimens.

Cheesman (1948), Simmonds (1962), and Perrier et al. (2009) reported that subspecies burmannica and siamea are distributed in overlapping areas from southeastern India and Myanmar to Vietnam. In these cases, it is suspected that the reported banana collections were too limited to be definitive. Cheesman (1948: 22) himself noted observing only a “dozen clones” of M. acuminata in the I.C.T.A. collection. Therefore, despite extensive surveys along the Thailand–Myanmar border from Mae Hong Son through Prachuap Khiri Khan, no “true” subsp. burmannica accession sensu Simmonds was found, and subsp. burmannica cannot be maintained in the traditional sense. It is argued that subsp. burmannica should be included within subsp. siamea, which possesses cuneate or oblique leaf bases; purple, reddish-purple to purplish-brown male-phase inflorescences; variable degrees of bract imbrication; and bract apices overlapping by more than 1 cm.

This argument is supported by the results of Diversity Arrays Technology (DArT), simple sequence repeat (SSR) markers, molecular cytogenetics, and genotyping-by-sequencing (GBS), which indicated that the two subspecies were not separated (Dupouy et al. 2019; Jenny et al. 2024).

According to the rules of botanical nomenclature (Turland et al. 2018), among the two subspecies proposed by Simmonds (1956), subsp. siamea takes precedence because it appeared earlier (page 466). Therefore, subsp. siamea is the accepted name, with subsp. burmannica (page 468) reduced to synonymy.

M. acuminata complex of subsp. microcarpa and subsp. truncata

Simmonds (1956) distinguished subsp. microcarpa from its counterparts “by the yellowish tinge and virtual waxlessness of the foliage; by the intense chocolate brown pigmentation of sheaths and, often, midribs; by the fading purple flush on the peduncle and male(-phase) rachis; by the plump non-imbricate male bud (male-phase inflorescence with bract apices not overlapping); by the bracts purple without and pale red within but weakly rolled at the time of falling; and by its essentially montane distribution. The fruits are variable in size.” All these morphological features, especially the male-phase inflorescence features (Fig. 5), are variably present in subsp. truncata, subsp. malaccensis, and subsp. siamea found in Thailand and could not be used for identification.

Simmonds (1956) reduced M. truncata to a synonym of M. acuminata subsp. microcarpa because of their similar morphology. However, AFLP and RFLP marker analyses recently revealed their distinct status (Carreel et al. 1994; Wong et al. 2001; Perrier et al. 2009). Previous literature stated that subsp. microcarpa was endemic to the lowlands of the island of Borneo (Nasution 1991; Wong et al. 2001) and that subsp. truncata is distributed in the highlands of Peninsular Malaysia (Carreel et al. 1994; Perrier et al. 2009). The fact that subsp. microcarpa, according to Simmonds’ description, could not be found in Thailand agrees with its geographic distribution and the genome assemblies recently reported by Perrier et al. (2011) and Rouard et al. (2018). Cheesman (1948) also mentioned that subsp. truncata plants were not vigorous under less humid and lowland conditions and ultimately died. It is suspected that geographic isolation may have caused subspecific polymorphisms between the two subspecies.

Distribution boundaries of M. acuminata subspecies

The survey results confirmed Simmonds’ (1956) view that Peninsular Thailand and the Thailand–Myanmar border are areas of “extreme complexity.” Musa acuminata subsp. truncata, as a new record for Thailand, extends its known natural distribution from mountainous areas of mainland Malaysia across the Thailand–Malaysia border. The results agree with earlier reports (Cheesman 1948; Simmonds 1956; Wong et al. 2001) that subsp. truncata is montane and does not thrive well at low altitudes, as the sole accession of this subspecies could not be maintained in the nursery near Bangkok.

Musa acuminata subsp. siamea is more drought- and heat-tolerant and is the most widespread of all the subspecies. It was found throughout northern, central, western, northeastern, and eastern Thailand, where a dry season of 3–6 months occurs. Evidence from other reports indicates that this subspecies has also been observed in southern China, Laos, and Vietnam (Wu and Kress 2000; Lheureux et al. 2007; Jenny et al. 2024). The absence of M. acuminata specimens from most of northeastern and eastern Thailand (Fig. 1) may be due to extensive and continuous deforestation in these regions. Meanwhile, subsp. microcarpa, which has not been found in Thailand, is probably restricted to the island of Borneo (Perrier et al. 2011; Rouard et al. 2018). However, field surveys of subsp. microcarpa in its natural habitats are needed to confirm its existence or its synonymy with subsp. siamea.

Based on the investigations, the distribution of M. acuminata subsp. malaccensis has been extended from southern Peninsular Malaysia to northwestern Thailand. This subspecies prefers cool conditions and continuous precipitation throughout the year. The morphological analysis did not support the assumption of De Langhe et al. (2000) that these northern populations were ‘pseudo-malaccensis.’ In contrast, it is believed that they are typical of their southern counterparts, and it is hypothesized that this subspecies might have been distributed along the mountain chain, which had the same climate pattern from south to north, since ancient times when the climate was colder and rainfall was higher. When the climate became warmer and drier, the distribution range receded. Some populations have persisted in isolated areas where the climate has remained wet and cool. Exploration along the rainward side of the Tanao Si/Tenasserim mountain chain in Myanmar would be important to provide more evidence for this hypothesis. Subspecies malaccensis was commonly found in the lowlands of southern Thailand and also grew in areas overlapping with populations of subsp. truncata in the highlands of Narathiwat and Yala. The fact that it was found at approximately 200–1,000 m above sea level in northern Thailand leads to the conclusion that it has a much wider altitudinal range than previously reported (Ridley 1924; Simmonds 1956; Nasution 1991; Wong et al. 2001; Perrier et al. 2009).

Deviation of M. acuminata subspecific forms

Three new taxonomic entities of M. acuminata are reported in this manuscript (Fig. 7): two forms with yellow bracts and one with a strikingly deviant inflorescence morphology. Many Musa taxa have been listed as having yellow bracts, e.g., M. basjoo Siebold ex Miq. (Miquel 1867), M. siamensis Häkkinen & Rich.H.Wallace (Häkkinen and Wallace 2007), M. acuminata var. flava (Ridl.) Nasution (Nasution 1991), and M. acuminata subsp. banksii (F.Muell.) N.W.Simmonds (Simmonds 1956). Forma byssina and forma luteola, described here, belong to M. acuminata subsp. siamea and subsp. kraburiensis, respectively. They are easily distinguished from M. acuminata var. flava, a native variety distributed in Kalimantan and on the Malay Peninsula, by lacking a cuneate or oblique leaf base and a convolute male-phase inflorescence. The name byssina refers to the bracts having a light yellow color reminiscent of raw silk. The name luteola denotes the golden-yellow color of egg yolk (Eckel 2010–2023).

In their natural habitats, f. byssina appeared to be less common than f. luteola. However, it may not actually be less common. The area south of Phanom Dongrek Mountain has many yellow-bracted populations, but they are patchily distributed over large areas and can grow only where there is sufficient moisture and limited human disturbance. Despite being observed in only one area of the Isthmus of Kra, the f. luteola population extended over 4 km, and the number of clumps reached up to 50. In contrast, f. byssina was represented by only a single clump at each of several locations among typical red-purple M. acuminata populations. Nevertheless, preliminary observations showed squirrels and bats visiting the yellow flowers of f. luteola at night and insects visiting during the day (W. Nilapaka, pers. obs.). The lighter bract color may attract these nocturnal and diurnal visitors. Bract color may be less important for pollinator attraction than floral scent and nectar or pollen rewards.

The extraordinary inflorescence architecture of M. acuminata subsp. siamea f. nanakornii (Fig. 7D) has attracted plant enthusiasts and researchers alike. Because of the infertility of the form, the three initial specimens collected were vegetatively propagated and grown by the villagers as ornamental plants. For research purposes, a clone found in Chiang Mai was introduced into the Queen Sirikit Botanic Garden, and Chomchalow et al. (2014) reported these bunch mutations for the first time. The aberration, in which a male-phase inflorescence replaces each flower on the hands of the banana bunch, is possibly caused by abnormalities involving flower and inflorescence meristem indeterminacy. This mutation might involve the abnormal expression of a transcription factor or other genes in related pathways. The genetic and hormonal regulation of inflorescence meristem activity has been reviewed in angiosperms (Thompson and Hake 2009) and studied in monocots, e.g., corn (Laudencia-Chingcuanco and Hake 2002; Chuck et al. 2008) and grasses (Bommert and Whipple 2018), and in dicots, e.g., cauliflower (Azpeitia et al. 2021). However, many studies of the genome, transcriptome, and cell and tissue differentiation are required because almost no studies of inflorescence formation in bananas have previously been conducted.

There are five main conclusions from this study. First, M. acuminata is discontinuous from the other related species investigated. Second, the use of subspecific rank within the M. acuminata complex is considered the most suitable way of dealing with the variation encountered in the wide-ranging collections of bananas throughout Thailand. Third, subsp. microcarpa has not been found in Thailand, and subsp. burmannica cannot be maintained and is reduced to synonymy with subsp. siamea. Fourth, the addition of subsp. kraburiensis as a newly described subspecies and subsp. truncata as a new record for the Thai flora brings the total number of Thai subspecies to four. Lastly, the taxonomic status of these four M. acuminata subspecies—kraburiensis, malaccensis, siamea, and truncata—found in Thailand is supported by morphology.

Based on this study, in addition to geographic distribution, the most important morphological characters for the determination of these M. acuminata subspecies are leaf base shape, rachis position, male-phase bract imbrication, and bract color. The minimal collection requirements for accurate identification are the base of one mature leaf, a male-phase inflorescence, and a hand of fully mature fruits. In addition, four series of photographs are needed: (1) the clump of pseudostems with a mature bunch showing the rachis position; (2) the leaf base and apex on their adaxial sides and the middle part of the leaf on its abaxial side to represent the waxiness and color of the underside; (3) the male-phase inflorescence and outermost bracts showing their shapes, external and internal bract colors, and reflexing after anthesis; and (4) the male flowers showing the adaxial side of the compound tepal, free tepal, stamens, and pistil. The standard color chart (e.g., IPGRI-INIBAP/CIRAD 1996) and a scale should always accompany all photographs.

For further studies of genetic variation, mixing among subspecies, and the actual natural distribution of M. acuminata subpopulations in relation to geographic locations, multilocus genetic assays such as SSR, SNP, or inter-MITE analyses are required.

Taxonomic treatment

M. acuminata

Colla, Mem. Gen. Musa 25: 394. 1820

7EBA254C-6B34-5709-9497-6C9B3BDC7CEA

Diagnosis.

Musa acuminata is distinguished from M. balbisiana by its revolute bracts, bare rachis, and non-clasping petiole canal margins, two rows of ovules in one locule; in contrast, M. balbisiana possesses imbricate bracts, a rachis with persistent bracts, and clasping petiole canal margins, four rows of ovules in one locule.

Type.

Rumphius (1747), Herbarium Amboinense 5: t. 61 Fig. 1, M. simiarum Pissang Jacki. (lectotype: designated by Häkkinen and Väre 2008).

Description.

Pseudostem of main shoot 1.4–7 m tall, 17–65 cm in circumference, light green, greenish yellow to medium green, with 1–6 suckers, often with large blotches. Leaf blade oblong, 80–340 by 25–95 cm, with or without blotches, with thin to thick wax cover, base cuneate or rounded to auriculate, more or less oblique, apically blunt; petiole 16–130 cm long, proximally with dark purple-brown blotches varying in size, margins inward curved to spreading. Peduncle glabrous, or covered by short hairs varying in density. Inflorescence curved or drooping; rachis bract lanceolate to elliptical or ovate, varying in color on the abaxial side from dark purple to orange-red, sometimes with yellow striation, revolute before falling. Flowers with ivory-colored perianth and yellow petals lobes, sometimes with pink tinge; female flowers with an ovate, inner adaxial tepal, green ovary, and ivory-colored stigma; male flowers with an elliptic free adaxial inner tepal, ivory-colored ovary, and yellow to orange stigma. Infructescence c. 120 cm long, drooping; peduncle 30–75 cm long, rounded in cross section and c. 4 cm across; 3–15 hands per bunch, 5–23 fruits per hand; biseriate male-phase rachis bracts not persistent after anthesis. Fruits inserted in two rows; pedicel 0.3–2 cm long; berry 5–12 long cm by 1.5–2.5 cm wide; apex bottle-shaped, 0.4–1.5 cm. Seeds brown to black, irregular in size and shape, angular in cross section, with rough surface.

Distribution.

India (Assam), Myanmar, Thailand, Laos, Vietnam, China, Malaysia, Indonesia (type), and Australia (Queensland).

Notes.

The most widely distributed species occurring throughout Thailand. Four subspecies are recognized here. Transitional forms have been observed in areas of overlapping distribution, suggesting possible hybrid zones.

Key to subspecies of M. acuminata

1 | Leaf base cuneate to oblique, bract apex overlapping 1–2 cm | 2
– | Leaf base round, cordate or auriculate, bract apex not overlapping or overlapping less than 1 cm | 4
2 | Bracts purple, bluish purple to purple brown | 3
– | Bracts yellow | M. acuminata subsp. siamea f. byssina
3 | Male-phase inflorescence on one rachis one | M. acuminata subsp. siamea f. siamea
– | Male-phase inflorescences on one rachis numerous | M. acuminata subsp. siamea f. nanakornii
4 | Peduncle and rachis purplish brown and dark purple, external bracts dark purple, internal bract ivory to pale red-purple fading to ivory at the base | M. acuminata subsp. truncata
– | Peduncle and rachis green, external and internal bracts purple, red-purple, red to orange red, rarely yellow | 5
5 | Rachis 2.5 cm or less in diameter, horizontal to pendulous; male-phase inflorescence apex directed downward | M. acuminata subsp. malaccensis
– | Rachis more than 3.0 cm in diameter, horizontal to ascending; male-phase inflorescence apex directed horizontally or upward | 6
6 | Bract red, orange-red, red purple or pink-purple | M. acuminata subsp. kraburiensis f. kraburiensis
– | Bract yellow | M. acuminata subsp. kraburiensis f. luteola

Musa acuminata Colla subsp. kraburiensis

Swangpol & Somana subsp. nov.

F1EDC7AB-0E39-5BDC-B3D5-31BCDBEE306C

urn:lsid:ipni.org:names:77394109-1

Fig. 9

Diagnosis.

Musa acuminata subsp. kraburiensis is distinguished from M. acuminata subsp. malaccensis, M. acuminata subsp. siamea and M. acuminata subsp. truncata by horizontal or angled upward rachis, rachis diameter more than 2.5 cm and male-phase inflorescence angled upwards.

Type.

Thailand: • Kapoe District, Ranong Province, 15 December 2023, with flowers, Swangpol & Somana 689 (holotype: BKF!).

Description.

Pseudostem of main shoot 1.7–4.0 m tall, 25–50 cm in circumference, light green, with 2–4 suckers. Leaf petiole 40–100 cm long, with small to large dark purple-brown to brown blotches, petiolar canal straight with erect margins; leaf blade 105–250 cm by 40–95 cm, with little or no visible sign of wax; basally rounded, cordate or auriculate. Inflorescence peduncle 15–40 cm long, sometimes with short hairs, in the female phase fusiform to conical in outline, 20–40 cm by 10–15 cm; in the male phase lanceolate to ellipsoid to ovate in outline, with apices of the inner rachis bracts completely concealed by the outer bracts; both sides of bracts covered by thin layer of wax, purple, red-purple, pink-purple to orange-red, rarely yellow, sometimes with yellow or red purple streaks on the abaxial side; bract revolute before falling. Rachis at anthesis horizontal or angled upwards, rachis diameter more than 3 cm, green, bracts leaving prominent scars after shedding. Flowers with ivory-colored perianth and yellow petals lobes; female flowers with an ovate, inner adaxial tepal, green ovary, and ivory-colored stigma; male flowers with an elliptic free adaxial inner tepal, ivory-colored ovary, and yellow to orange stigma. Infructescence. Infructescence horizontal, with 4–15 hands per bunch and 5–24 fruits per hand. Fruit pedicel 0.5–1.0 cm long; berry 2–10 cm by 1.3–3.0 cm; apex bottle-necked, 0.5–1.5 cm. Seeds brown to black, angular in cross section, with rough surface.

Figure 9.: Musa acuminata subsp. kraburiensis Swangpol & Somana, subsp. nov. A. Clump; B. A leaf showing the base and apex; C. A transverse section of the petiole; D. A female-phase inflorescence; E. A male-phase inflorescence; F. Flowers showing, from left to right, a female flower, a female flower without the tepals, a compound tepal and a free tepal of a female flower, a free tepal and a compound tepal of a male flower, five anthers, a pistil, and a male flower; G. Left, a hand of fruits, and right, transverse and longitudinal sections of fruits. Illustrated by Narongsak Sukkaewmanee; graphic by Sasivimon C. Swangpol and Wandee Inta.

Distribution and habitat.

Endemic to the Kra Isthmus, at ca. 9–10.5°N, in Peninsular Thailand along the Tanao Si/Tenasserim mountain chain. The northern border of the distribution area extends from Pathio to Phato District, Chumphon Province, and ends in Suk Samran District, Ranong Province.

Ecology.

Scatter populations of this subspecies are found on hills, slopes, and open areas near streams along Routes No. 4 and No. 4006 and in fruit orchards in Amphoe Lang Suan.

Etymology.

The epithet kraburiensis refers to the Kraburi River basin in the vicinity of the Kra Isthmus, where this taxon is endemic.

Vernacular.

Kluai Pa Kraburi (Thai: กล้วยป่ากระบุรี, “wild banana from Kraburi”).

Notes.

The Kra Isthmus area where subsp. kraburiensis was found is in the biogeographic transition zone between two floristic provinces, Indochinese and Sundaic (Woodruff 2003). The subspecies is possibly a natural fertile hybrid connecting subsp. siamea at the southernmost end of its distribution boundary with the northernmost area of subsp. malaccensis in Peninsular Thailand. At the boundary in Amphoe Tha-Sae, Changwat Chumphon, there are also subsp. siamea–subsp. kraburiensis hybrid-like plants. Meanwhile, in Amphoe Lang Suan and Amphoe Phato, Changwat Chumphon, subsp. kraburiensis grows alongside subsp. malaccensis. A yellow-bracted form of this subspecies is found in Changwat Ranong.

M. acuminata Colla subsp. kraburiensis

Swangpol & Somana f. luteola Swangpol & W.Inta f. nov.

86C3527D-751F-53FD-AA7A-56D3BC11FFF7

Diagnosis.

Musa acuminata subsp. kraburiensis f. luteola is distinguished from f. kraburiensis by its yellow bracts, whereas the male bracts of f. kraburiensis are typically red to orange-red, or occasionally red-purple to pink-purple.

Type.

Thailand: • Kapoe District, Ranong Province, 15 December 2023, with male-phase inflorescence, Swangpol & Somana 690 (holotype: BKF!); • Mueang Ranong District, Ranong Province, 24 September 2016, with male-phase inflorescence, Swangpol & Somana 601 (paratype: BKF!).

Description.

Pseudostem of main shoot 2–3.5 m tall, 20–45 cm in circumference, light green, with 2–4 suckers. Leaf petiole 60–80 cm long, without blotches or with small to large dark brown blotches, petiolar canal straight with erect margins; leaf blade 140–250 cm by 50–80 cm, with little or no visible sign of wax; basally rounded, cordate or auriculate. Inflorescence peduncle 15–35 cm long, sometimes with short hairs, in the female phase fusiform to conical in outline, 20–40 cm by 10–15 cm; in the male phase lanceolate to ellipsoid to ovate in outline, with apices of the inner rachis bracts completely concealed by the outer bracts; both sides of bracts covered by thin layer of wax, yellow; bract revolute before falling. Rachis at anthesis horizontal or angled upwards, rachis diameter more than 3 cm, green. Flowers with ivory-colored perianth and yellow petals lobes; female flowers with an ovate, inner adaxial tepal, green ovary, and ivory-colored stigma; male flowers with an elliptic free adaxial inner tepal, ivory-colored ovary, and yellow to orange stigma. Infructescence horizontal, with 5–10 hands per bunch and 5–20 fruits per hand. Fruit pedicel 0.5–1.0 cm long; berry 6–7.5 cm by 1.7–2.0 cm; apex bottle-necked, 0.5–1.5 cm. Seeds brown to black, angular in cross section, with rough surface.

Distribution and habitat.

Endemic to a single location in Ranong Province, Thailand. It is estimated that no more than 30 clumps of this yellow-bracted forma grow sparsely on a hillside in an area of approximately 10 km2.

Vernacular.

Kluai Pa Kraburi Pli Lueang (“wild banana from Kraburi with yellow buds” –in Thai), Kluai Pa Kraburi Si Thong (“golden wild banana from Kraburi” –in Thai).

Notes.

The plant is possibly a natural mutant of M. acuminata subsp. kraburiensis. Observations indicated that the yellow-bracted forma attracts squirrels, birds, and insects similarly to the red-bracted counterpart; however, the former appears intolerant of strong sunlight, weaker, and less numerous than the latter. The population is highly threatened by land clearing for agricultural purposes and road expansion.

Musa acuminata Colla subsp. malaccensis

(Ridl.) N.W.Simmonds, Kew Bull. 11, 3, 1956: 463–489

8AD39ABC-0D3C-5E29-B65D-D433557B8434

Type.

Malaysia [Selangor, Pahang], 1891, Henry Nicholas Ridley (lectotype: SING 062891).

Distribution and habitat.

Thailand • Northern: Tak (Doi Musoe, Along the Road Nos. 105 and 1090, Namtok Pa Wai), Mae Hong Son (Ban Mae Sam Lap); • Peninsular: Surat Thani (Surat Thani Rubber Research Station, Along the Road No. 401), Phangnga (Lam Pakarang, Khao Lak-Lam Ru NP, Along the Road No. 4), Phuket (Along the Road No. 402), Krabi (Wat Tham Suea, Khao Phanom Bencha Forest Park, Tha Pom Klong Song Nam), Nakhon Si Thammarat (Along the Road No. 401, Namtok Phrom Lok), Phatthalung (Khao Pu – Khao Ya NP, Khao Chai Son), Trang (Namtok Sai Rung), Satun (Namtok Than Plio, Thale Ban NP), Songkhla (Along the Road No. 42, Namtok Ton Nga Chang, Khao Kho Hong), Pattani (Namtok Mai Khao), Yala (Namtok Sukthalai, Betong Hospital, Along the Road No. 401), Narathiwat (Hala-Bala Wildlife Sanctuary).

Ecology.

Open areas at the edge of the forest, from 10–780 m a.s.l.

Vernacular.

Kluai Thuean and Kluai Pa, both mean “wild banana” –in Thai, Kluai Pa Malaka (“wild banana from Malacca” –in Thai).

Notes.

This subspecies is widespread throughout Peninsular Thailand and has recently been documented in new locations within the northwestern provinces but is absent from the southwestern and central areas. It is expected to occur across the border in Myanmar on the western side of the Tenasserim Range.

Musa acuminata Colla subsp. siamea

N.W.Simmonds, Kew Bull. 11, 3: 463–489. 1956

93F6E37F-9A68-5A51-8482-6F52EF867553

Type.

Trinidad, ICTA introduction no. 403, Simmonds 18834 (holo: K!).

Musa acuminata Colla subsp. siamea

N.W.Simmonds f. byssina Swangpol & Athawongsa f. nov.

6F5F96CC-760F-5A93-8ECC-08D3AD8501B1

Diagnosis.

Musa acuminata subsp. siamea f. byssina is distinguished from other forma by its yellow bracts, whereas bracts that are purple, bluish-purple, or purple-brown with yellow tips are commonly found in f. siamea and f. nanakornii.

Type.

Thailand • Pak Chong District, Nakhon Ratchasima Province, 20 January 2006, with male-phase inflorescence, Swangpol & Samana 173 (holotype: BKF!); • Pong Nam Ron District, Chanthaburi Province, 21 January 2006, with male-phase inflorescence, Swangpol & Samana 177 (paratype: BKF!)

Description.

Pseudostem of main shoot 2–3 m tall, 30–40 cm in circumference, light green, greenish yellow to medium green, with 3–4 suckers. Leaf petiole 45–60 cm long, with or without dark purple brown blotches, petiolar canal with erect margins; leaf blade 170–200 cm by 35–60 cm, covered by thin to thick layer of wax; basally oblique, left side cuneate, right side rounded, to cuneate. Inflorescence peduncle 20–40 cm long, with dense cover of short hairs, in the female phase fusiform to conical in outline, 20–40 cm by 10–15 cm; in the male phase 15–25 cm by 5–10 cm, with apices of the inner rachis bracts exposed, on the both side yellow, covered by thin layer of wax; bracts revolute before falling. Rachis drooping at male anthesis, rachis diameter usually less than 2.5 cm in diameter, green. Flowers with ivory-colored perianth and yellow petals lobes; female flowers with an ovate, inner adaxial tepal, green ovary, and ivory-colored stigma; male flowers with an elliptic free adaxial inner tepal, ivory-colored ovary, and yellow to orange stigma. Infructescence. Infructescence drooping, with 6–10 hands per bunch and 10–25 fruits per hand. Fruit pedicel 0.5–1.6 cm long; berry 7–10 cm by 1.8–2 cm; apex bottle-necked, 0.5–1.0 cm. Seeds brown to black, angular in cross section, with rough surface.

Distribution and habitat.

Endemic to Thailand. Found rarely in Chanthaburi, Nakhon Ratchasima, and Kamphaeng Phet provinces.

Ecology.

Grows in shade at the edge of the forest and in disturbed areas, on low slopes or in open areas.

Etymology.

The epithet byssina refers to the yellow color of a raw silk cocoon, representing the color of the plant’s inflorescence bracts.

Vernacular.

Kluai Pa Pli Leung (“yellow bud banana”—in Thai), Suwannakhattali (“golden banana”—in Thai), and Kluai Pa Mai Thong (“golden silk banana”—in Thai).

Notes.

A yellow mutant occurring naturally but rarely. The degree of yellowish-pink coloration varies among specimens found in Kamphaeng Phet, Nakhon Ratchasima, and Chanthaburi, and they are suspected to be unrelated mutants.

Musa acuminata Colla subsp. siamea

N.W.Simmonds f. nanakornii Swangpol, Chom. & Sukkaew. f. nov.

E6B55A5F-4E9F-5E56-A159-9F0A1C186C78

Fig. 10

Diagnosis.

Musa acuminata subsp. siamea f. nanakornii is similar to f. siamea based on its oblique to cuneate leaf base. It is distinguished from f. siamea by male inflorescences per rachis numerous, each with long rachilla branches from each flower bud. Female flowers, mostly infertile, occasionally produce fruits with a few seeds.

Type.

Thailand • Khek Noi, Phetchabun Province, 2 February 2006, with male-phase inflorescence, Sukkaewmanee s.n. (holotype: BKF!); • Phop Phra District, Tak Province, 4 October 2010, with male-phase inflorescence, Swangpol & Somana 442 (paratype: BKF!)

Description.

Pseudostem of main shoot 2–3 m tall, 40–50 cm in circumference, light green to green yellow, with 2–6 suckers. Leaf petiole 70–80 cm long, with or without brown blotches, petiolar canal with erect margins; leaf blade 200–250 cm by 60–80 cm, covered by thin to thick layer of wax; basally oblique. Inflorescence peduncle 40–45 cm long, with dense cover of short hairs, in the female phase fusiform to ovate, 30–40 cm by 25–30 cm, female flowers mostly infertile; in the male phase inflorescences per rachis numerous, rachis bracts of both sides purple, purple-brown, red-purple to pink-purple, yellow apices, on the inner (adaxial) side covered by thin layer of wax; bracts revolute before falling. Rachis drooping, with rachilla branches of lateral buds and abnormal flowers. Infructescence drooping, with 4–6 hands per bunch and 8–20 fruits per hand. Fruit is often undeveloped.

Figure 10.: Musa acuminata subsp. siamea f. nanakornii Swangpol, Chom. & Sukkaew, f. nov. A. A hand of withering female flowers; B. An aberrant female flower; C. An inflorescence with hands of aborted female flowers and a primary male-phase inflorescence with numerous hands of secondary male-phase inflorescences on extended rachillas; D. Two male flowers, left, a normal flower, and right, an abnormal flower; E. A hand of secondary male-phase inflorescences without an extended rachilla. Illustrated by Narongsak Sukkaewmanee; graphic by Sasivimon Swangpol and Wandee Inta.

Figure 11.: Musa acuminata subsp. truncata (Ridl.) Kiew. A. Clump; B. A leaf showing the base and apex; C. A transverse section of the petiole; D. A female-phase inflorescence; E. A male-phase inflorescence; F. Flowers showing, upper row from left to right, a female flower, a compound tepal, a pistil, five anthers, and a free tepal of a female flower, and lower row from left to right, a compound tepal, five anthers, a pistil, a free tepal of a male flower, and a male flower; G. Left, a hand of fruits, and right, transverse and longitudinal sections of fruits. Drawn by Narongsak Sukkaewmanee; graphic by Sasivimon C. Swangpol and Wandee Inta.

Distribution and habitat.

In cultivation in northern and northeastern Thailand (Tak, Phetchabun, and Nan). Probably also in Laos.

Etymology.

The formal name is dedicated to Dr. Weerachai Nanakorn, former President of the Botanical Society under the Patronage of HM Queen Sirikit of Thailand and former Director of the Queen Sirikit Botanic Garden (QSBG), who introduced this clone into cultivation at QSBG in 2009.

Vernacular.

Kluai Roi Pli (“one-hundred-bud banana”—in Thai), Kluai Khom Raya (“chandelier banana”—in Thai).

Notes.

The banana is a natural mutant. Its numerous male-phase inflorescences are differentiated from the original male flowers and have extended rachillas of varying lengths. All accessions found in three provinces were grown by Hmong hill-tribe villagers as ornamental plants. The male-phase inflorescences are sometimes eaten because they are believed to promote fertility in both men and women.

Musa acuminata Colla subsp. truncata

(Ridl.) Kiew, Ann. Bot. 88, 6: 1025. 2001

E57D17D1-C435-50EC-89F1-FEA59AA8FAFD

Type.

Malaysia [Selangor, Pahang], 1905, Henry Ridley 13694 (lectotype: SING).

Description.

Pseudostem of main shoot 3–6 m tall, 30–45 cm in circumference, light green, with 2–4 suckers, often with large blotches. Leaf petiole 50–100 cm long, with small to large, dark purple-brown blotches, petiolar margins erect; leaf blade 155–245 cm by 55–75 cm, with little or no visible sign of wax; base obliquely rounded, typically with a more distal left-handed side. Inflorescence peduncle 18–43 cm long, with short hairs varying in density, in the female phase fusiform to conical in outline, 20–40 cm by 10–15 cm, in the male phase with ovate rachis bracts ovate, 10–23 cm by 7–10 cm; apices of the inner rachis bracts completely concealed by the outer bracts, apically acute, revolute before shedding, ivory-colored or pale red-purple fading to ivory at the base on the inner (adaxial) side and dark purple without yellow tips on the outer (abaxial) side, not persistent after anthesis. Rachis drooping at male anthesis, rachis diameter usually less than 2.5 cm in diameter, purplish brown to dark purple. Flowers with ivory-colored perianth and yellow petals lobes; female flowers with an ovate, inner adaxial tepal, green ovary, and ivory-colored stigma; male flowers with an elliptic free adaxial inner tepal, ivory-colored ovary, and yellow to orange stigma. Infructescence. Infructescence horizontal or slightly curved downward, with 4–15 hands per bunch and 15–28 fruits per hand. Fruit pedicel 1.2–2 cm long; berry 10–12 cm by 1.5–2 cm. Seeds brown to black, angular in cross section, with rough surface.

Distribution and habitat.

Thailand • Peninsular: Narathiwat (Sukhirin, close to Hala-Bala Wildlife Sanctuary Wang, Ban Sai Borisat, Namtok Chat Warin Sungai Padi, along highway no. 4077 Sri Sakorn), Yala (Betong, KERR 7643, BM), Songkla (Ban Pian, KERR 14821 BM).

Ecology.

Hill and montane tropical forests, at 90–750 m altitude.

Etymology.

The epithet truncata refers to the “truncate apex” or square end of the leaves (Ridley 1909).

Vernacular.

Kluai Thuean (meaning “wild banana”) was used in southernmost Thailand as mentioned by Simmonds (1956) for M. acuminata subsp. microcarpa and referred to Kerr specimens in which this vernacular name was applied to both M. acuminata subsp. siamea and M. acuminata subsp. microcarpa; Kluai Pa (also means “wild banana”), Kluai Pa Pli Muang (“purple-bud wild banana”—in Thai).

Notes.

A new record for Thailand. Simmonds (1956) previously mentioned this subspecies native to Thailand as M. acuminata subsp. microcarpa. Hybrids of M. acuminata subsp. truncata and M. acuminata subsp. malaccensis were found growing together in Changwat Yala. The hybrids possess bracts with an intense red color internally.