Gigantochloa thoii

Gigantochloa thoii K.M. Wong

Sandakania 1: 18 (1992).
2n = unknown

Origin and geographic distribution
G. thoii is known only in cultivation in Peninsular Malaysia. For map click: Map308.TIF. Holttum surmises a Thai-Burmese origin for many Gigantochloa species now known only in cultivation in South-East Asia but, despite the poor state of bamboo exploration in Burma (Myanmar), no evidence has been found that this species exists there.

The young shoots of G. thoii are relished as a vegetable-delicacy. Although the culms are large and strong, they are not taken for any industry, probably because culms from adequately abundant wild populations of two other Gigantochloa bamboos, G. scortechinii Gamble and G. wrayi Gamble, are available, whereas G. thoii has not yet been planted as such a resource.

Production and international trade
There are no recorded economic and production data, as the shoots are used for local consumption only. They are usually sold in small quantities obtained from clumps grown in villages.

Densely tufted, sympodial bamboo. Culm erect, up to 16 m tall, diameter up to 12 cm, plain green; internodes copiously white-waxy, scantily dark-brown hairy at the upper part; nodes not conspicuously swollen. Branches at each midculm node arising from a single bud consisting of a dominant primary branch, with (usually) one subdominant secondary branch from its base on each side, and several lesser leafy branchlets from the base of secondary branches. Culm sheath pale to medium green, with dark brown hairs on the back; blade broadly lanceolate, green, spreading to reflexed; ligule lacerate, the base 2-4 mm long, the lacerations 5-18 mm long; auricles large lobes to 10 mm long, with bristles 10-18 mm long on the margin, dark green to purplish-green. Leaf blade 8-32 cm x 2-6 cm, lower surface softly pale-hairy; ligule shortly toothed, 0.5-1.5 mm long; auricles small lobes, with fine bristles to 4 mm long on the margin. Pseudospikelet 10-15 mm long, with 2-3 gemmiferous bracts, 2-3 glumes, 4-5 perfect florets and a vestigial terminal floret usually represented by an empty lemma. Caryopsis unknown.

Growth and development
Young shoots mainly develop during the rainy season. Flowering occurs in just a few culms in the clump, or can sometimes involve an entire clump. Reproductive culms senesce after flowering but regeneration from rhizomes in clumps that have senesced is possible. Flowering extends over many months in a fertile clump, but no seed has been found thus far.

Other botanical information
Several features allow G. thoii to be easily distinguished from true G. levis which is a common bamboo in the Philippines and Sabah, with which it has been confused in the past. G. thoii has white-waxy culms and the basal internodes are scantily dark-haired at the upper part only; its floret has no lodicules, a palea with a 2-4-veined back and the anther apical cusps bear long spines c. 0.1 mm long. True G. levis has culms which are non-waxy, and basal internodes that are densely dark-haired all over; its floret has 3 lodicules, a palea with a 4-5-veined back, and the anther apical cusps bear only short triangular spines hardly 0.05 mm long.

G. thoii is grown under tropical lowland conditions of Peninsular Malaysia.

Propagation and planting
Either rhizome cuttings (offsets) or culm cuttings may be used for vegetative propagation. Cultivated clumps from which new shoots are frequently removed for food develop rooted rhizome-like swellings at branch bases. Such 'aerial rhizomes' may be useful as vegetative planting material. It is likely, as has been demonstrated for some species of Bambusa, that regular debudding of rhizomes and removal of newly emerged culm shoots can encourage the development of 'aerial rhizomes'. Planting distance in the field is 3.5 m x 3.5 m.

Weeding was noted as an important aspect in the now non-existent shoot-producing G. thoii plot at Kepong. This could have been because the clumps were rather open in structure due to regular removal of shoots, leaving behind only several leafy mature culms. No reliable data on fertilizer application could be obtained.

Diseases and pests
The brown lesion disease, caused by Colletotrichum spp., can bring about serious damage. Heavy infestation of the leaves and subsequent insect attack can cause withering of foliage and senescence. The disease manifests as brown spots coalescing to form lesions. Fungicides such as thiram, benlate or captan have been recommended as prophylactics and control measures. Regular cleaning of bamboo clumps has been suggested, to reduce the risk of such infestation.

Only one incidence of an organized farm of G. thoii is known. The small holding of about 4.5 ha of G. thoii, in Kepong near Kuala Lumpur in Peninsular Malaysia, was said in 1983 to have had a young shoot production of up to 1000 katties (6000 kg) per week; off-peak production was estimated at 200-400 katties (1200-2400 kg) per week. The farm was started before 1957 but does not exist any more.

Handling after harvest
G. thoii shoots have so far only been sold fresh, or (after removal of sheaths) maintained in a brine solution. However, there is no standard prescription.

Genetic resources and breeding
As G. thoii exists only as cultivated clumps in Peninsular Malaysia and seeding has not been observed so far, it is likely that the genetic base will remain narrow. There are no germplasm collections and breeding programmes.

The excellent quality of G. thoii shoots for table use suggests it has potential as a plantation crop for bamboo-shoot production. However, bamboo shoots probably cannot form the sole raw material for a profitable canning or dried food industry because the required scale would involve cultivation on very large farms and shoot production is only seasonal.

K.M. Wong

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