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New Guinea, a centre of diversity

Winged bean exhibits considerable diversity (cick here to see) across its distribution. This observed diversity reaches its zenith in the island of New Guinea, where in just one location, Mt Hagen, 48 named varieties have been recorded. This diversity led to speculation that New Guinea itself might be a natural Centre of Origin for the winged bean.

An experiment:

In part to test this hypothesis, a variety trial was planted out in Malaysia in 1978, in which 135 winged bean accessions- representative of collections from Papua new Guinea, Indonesia, Malaysia, Thailand, and Sri Lanka - were grown under artificially extended daylength conditions, as well as in natural equatorial daylengths.

Malaysia experiment
Under lights

135 winged bean accessions, replicated twice, growing under lights
(another block of the 135 accessions was grown without lights)

The results:

Forty seven characteristics were measured on these 135 accessions. The assembled data was then analysed statistically.

The results confirmed that the highlands of New Guinea is a unique centre of diversity for the winged bean (Table 1).

Multivariate analysis

Multivariate Statistical Analysis (click here to see)

However, there was no direct support in the data for the hypothesis that New Guinea is the Centre of Origin for the species. This trial and a supplementary replicated variety trial (click here to see) showed that Papua New Guinea varieties as a whole are earlier to mature, have fewer low-growing branches, and have higher mature seed yields at day 165 after planting (Table 2). These were all signs that the New Guinea varieties of winged bean were typical of a more advanced domesticate.

Comparison of varieties

Comparison of winged bean varieties (click here to see)

Of all the varieties tested, the one group of accessions that had the characteristics most expected of an imagined prototype for the species, was the group of accessions from Bogor in the island of Java. This group of accessions failed to flower in the 165 days allotted to the experiment, had strong horizontal branching from low down on the main stem and leaf nodes which quickly formed roots when in contact with moist soil, and had a sparse flowering habit when they eventually did flower (Table 2).

Other varieties tested were intermediate between the New Guinea and the Bogor collections.

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