The Sweet Potato Ipomoea batatas
The kumara, more commonly known internationally as sweet potato
(also sweetpotato), Ipomoea batatus (L.) Lam., belongs to the Convolvulaceae Family.
The world 1999 sweet potato production has been estimated to be 137,126,043
t, with 9,520,353 ha harvested with an average yield of 14.40 t/ha (FAO
1999). Sweet potato is a perennial plant commonly cultivated as an annual
crop. Under appropriate growing conditions it forms starchy storage roots
(tuberous roots). Storage roots contain about 50-79% starch and 4-15%
sugar on dry weight basis or 7-28% starch on a fresh weight basis. Fresh
storage roots can also be a source of vitamin C, provitamin A, vitamin B
(thiamine), and iron. The sweet potato is mainly grown in tropical and
warmer temperate regions of the world. Optimum yields of I. batatus are
obtained from crops grown in moderate rainfall areas (750- 1250 mm) and
temperature range of 22-25 deg C and fertile light soils are preferable.
Pre-European Maori grew kumara as an annual crop. At the time of first European contact
many different varieties existed. Colenso collected the names of 48
varieties and Best gives the names 82 varieties plus 14 from other
sources. Many of these were undoubtedly iwi or regional synonyms. In 1963
when Doug Yen published information about his collection of kumara
varieties only four pre-European varieties remained. They are 'Rekamaroa',
'Hutihuti', 'Taputini' and 'Houhere'. Our first seasons results show that
'Taputini' performs well under 100 year drought conditions and it likely
that different varieties were selected for different conditions. It raises
the interesting question as to whether 'Taputini' may perform better than
modern varieties under drought conditions.
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