|Authors: ||R.J. Martin, G.P. Savage, B. Deo, S.R.P. Halloy, P.J. Fletcher|
|Keywords: ||Oxalis tuberosa, yam, tuber, virus, oxalate, taste, colour, cultivar|
Oca (Oxalis tuberosa, also known as New Zealand yam in New Zealand) is a staple South American tuber crop that has been grown in New Zealand for over a century from a narrow genetic base.
Recently a wider range of genetic material with a greater diversity of tuber colours was collected in the Andes and evaluated in New Zealand.
The introductions were assessed for and cleared of virus, then evaluated in the field.
Tubers from the field trials were tested for oxalate levels and consumer tested for appearance and taste.
Twelve lines were cleared of virus quickly, and were multiplied up in agronomic field trials.
In the field, the crop was managed similarly to potatoes, although oca sets tubers much later.
Experimental yields have been up to 20 t/ha before frosts killed the tops.
There was a two-fold variation in oxalate levels between cultivars, but levels of oxalate were not as high as in some other consumer foods.
The oxalates were all in the soluble form.
Consumer acceptability in terms of colour, flavour, texture and overall acceptability differed between cultivars.
Cultivars with red skin, bright yellow flesh colour, a slightly mealy texture and a sweet taste were preferred.
The results of these assessments have led to an oca breeding programme to incorporate desirable traits, and the first new cultivar has recently been released.
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