On the identity of Musa sp. 'Yunnan'

D R Constantine, Bridgwater, Somerset, U.K.
Chamaerops No.47 - published online 25-06-2003

- Left: Musa itinerans flowering in a field collection (probably at the Phu Ho Fruit Research Centre) in Vietnam.
Photo: Markku Häkkinen.
- Middle: Yunnan" flowering for the first time in cultivation in the Harry P. Leu Gardens, Orlando, Florida.
Photo: Eric Schmidt.
- Right: Well grown vegetative plant of "Yunnan" in the garden of Marc Vissers, Belgium. The waxy pseudostem and bluish hue of the plant, although different from the type description of M. itinerans, seems typical of the appearance of the plants in cultivation in Europe.
Photo: Marc Vissers

In February 2000, Toby Spanner introduced seed of Musa sp. "Yunnan" into commerce with the following announcement in his newsletter:

Musa sp. "Yunnan" - Yunnan Banana
These seeds originally came in as the rare Ensete wilsonii, the Snow Banana; however, seed shape and size suggest that the seeds are not Ensete but Musa sp. Our collector insists that the seeds were collected at very high altitude in China's Yunnan province, where Ensete wilsonii usually grows up to 2700 m (9000 ft.). Even with its identity not cleared yet we think this could be a very interesting cold hardy species that would probably thrive under the same conditions as the legendary Musa basjoo and M. sikkimensis.

From the outset, "Yunnan" aroused particular interest in horticulture because of its hoped for cold tolerance and its graceful, garden worthy habit. Some were also intrigued by its enigmatic origin.

As part of a wider study, a Finnish Musa researcher named Markku Häkkinen made a comparison in 2002 of seed and seedlings of "Yunnan" and a Vietnamese banana known as Chuoi Rung Hoa Soan (CRHS). Markku found that in the physical characteristics of the seed and the vegetative characteristics of the young plants, "Yunnan" and CHRS appeared to be identical.

CHRS was first found in north west Vietnam by an INIBAP/VASI collecting mission in 1994. The plant was given the accession number VN1-054 and in an internal VASI report it was identified as Musa itinerans. The precise basis for the identification is not clear but it seems to have been made because of the similar habit in the field of CHRS and Musa itinerans (Chuoi Rung in Vietnam). Musa itinerans is characterised by its extremely long rhizomes so that suckers pop up two metres or more away from the parent stem. This characteristic astonished scientists at the Imperial College of Tropical Agriculture in Trinidad who were the first to describe the species. The name of the species derives from this itinerant habit which was also reportedly seen in CRHS in the field in Vietnam.

Markku's work seemed to indicate that "Yunnan" and CRHS were one and the same. Markku discussed his work with Liu Aizhong, a specialist in Chinese Musaceae, who confirmed that Musa itinerans was rather common in Yunnan. It seemed, therefore, not to be very surprising that the seed collected in Yunnan and offered to Toby was indeed Musa itinerans. Markku and Aizhong's conclusion was the basis of Toby's note in his March 2002 newsletter that "Yunnan" was Musa itinerans:

With the help of some dedicated "Musophiles" in Finland and China, we were finally able to identify the banana that we have been distributing as Musa sp. "Yunnan". It seems to be Musa itinerans, a species fairly widely distributed in China, but as to our knowledge, still very rare in cultivation.

Doubts remained. The remarkable suckering habit of Musa itinerans had not been reported in plants of "Yunnan" in cultivation. Seedlings suckered profusely, but always close to the parent stem; close even in comparison to other Musa species. There were other vegetative dissimilarities noted between "Yunnan" in cultivation and the type description of Musa itinerans in the botanical literature. For example, "Yunnan" is a rather waxy plant whereas the leaf sheaths and petioles of Musa itinerans are devoid of wax. The leaf apex of Musa itinerans is truncate and the base rounded whereas the leaf apex of "Yunnan" is somewhat acute and the base distinctly auriculate. Musa itinerans has the robust vegetative habit and stature of a cultivated banana, whereas "Yunnan" has a rather slender, graceful habit.

The type description of Musa itinerans was based on plants growing in the open ground in Trinidad from Burmese seed, whereas the features of "Yunnan" mentioned here were from plants growing under glass in Europe from Chinese seed. These vegetative differences could simply represent a spectrum of types within Musa itinerans. Further, there was no information from European plants on inflorescence characteristics that are critical in diagnosing a species. Despite these shortcomings, the apparent differences in vegetative characteristics were nonetheless intriguing, and discussion continued. In April 2002, in an exchange of E-mails on this subject with Markku and Aizhong, Markku provided pictures of the male bud of CRHS taken in Vietnam during the INIBAP/VASI mission. It thus became possible to compare the male bud of CRHS with that of Musa itinerans. They were immediately seen to be completely different.

Musa itinerans has a rather plain, convolute male bud whereas CRHS has an extraordinary, colourful and very distinctly imbricate male bud. In one published report, the INIBAP/VASI mission described the inflorescence of CRHS as having "bright yellow bracts with distinctive dried up tips arranged spirally on the markedly imbricate male bud".

From the photographic evidence, it seemed obvious that "Yunnan"/CRHS could not be Musa itinerans. Rather, it seemed clear that "Yunnan"/CRHS, was a hitherto unrecognised, new Musa species.

The discovery of a new Musa in Vietnam (CRHS) would not be very surprising as much of that country is biologically, let alone botanically, little explored. However, the discovery of a new Musa in China ("Yunnan") and in highly botanised Yunnan of all places would be very surprising indeed. Liu Aizhong knows more about Chinese bananas than anyone, from the field as well as the herbarium, and has done much to clarify the tremendous confusion in the Chinese literature on Musa. Yet, Aizhong did not recognise CRHS at all, and neither did another great authority on the bananas, George Argent of RBG Edinburgh.

The evidence suggested that "Yunnan"/CRHS could not be Musa itinerans. Then, in August 2002, Eric Schmidt published photographs of "Yunnan" flowering in cultivation for the first time at the Harry P. Leu Gardens in Orlando, Florida. This turned the story on its head.

Eric published two photographs of the inflorescence of "Yunnan" on the Zingiber discussion group Internet site. Eric's photographs clearly showed that the inflorescence of "Yunnan" resembled Musa itinerans and not CRHS. Despite the fact that the Leu Gardens plants do not show the long suckers but form "a tight clump with very slender stalks", it seemed that "Yunnan" was Musa itinerans after all!

The identification of "Yunnan" as Musa itinerans seems to be correct, although we are still left with some questions. "Yunnan" and CRHS cannot be the same species, however similar the seed and young plants appeared to be in Markku's study. Was Markku supplied with seed of Musa itinerans in the first place and not CRHS? It seems clear that the determination of CRHS as Musa itinerans in the internal VASI report is wrong. So what is CRHS? It really does seem to be a new, hitherto unrecognised species.

What is the significance of the discrepancies in the vegetative characteristics of "Yunnan" and the type description of Musa itinerans? It may be significant that the type was described from a very limited sampling of the species from Burma rather than from knowledge of the species across its range in the field. Is it significant that while "Yunnan" suckers freely in cultivation, long, itinerant rhizomes so characteristic of Musa itinerans have not yet been reported, even on flowering plants of "Yunnan" grown in the open ground at the Harry P. Leu Gardens in Florida? It is possible that "Yunnan" represents a distinct subspecies of M. itinerans. Although the botanical affiliations of the plant are not fully known, it seems reasonable now to treat Toby's "Yunnan" as a cultivar, namely M. itinerans "Yunnan".

Among other things, this story reveals that there is still much to discover about the wild Musa species of Asia and that we may expect further exciting introductions. We await the formal description of CHRS as a new species, and possibly the first to have been "discovered" via the Internet! There will surely be more to come on this subject in the future.

D R Constantine maintains a website on the Musaceae

 

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