types. The best, selected after tests in several areas, was 'Jakiri'. 

 The following data suggest the promise of this variety: 



Cultivar 



Days to 

 ynature 

 250-270 

 210-240 

 270-290 



Yield 

 (tonnes /hectare) 



Protein 

 (% dry matter) 



D. rotundata 'Oshei' . 

 D. duinetorum 'Jakiri' 

 D. cayenensis 'Batibo' 



22-30 

 30-45 

 12-18 



9.0 

 10.2 

 7.8 



In a study of a small collection of D. dumetorum in western Puerto 

 Rico over several years, varietal differences were noted in the following 

 characteristics: thorniness of the stem, anthocyanin content and pubes- 

 cence of the stem, thorniness of the petiole, overall leaf shape, folding 

 and pubescence of the leaves, tuber shape, branching tendency and site 

 of branching, irregularity of the tuber, rugosity of the cortex, amount 

 of surface roots, flesh color, amount of gums exuded on cutting the 

 tuber, ability to sting the flesh, ease of peeling, boiling time required, 

 stickiness of the cooked tuber, flavor, and bitterness. These differences 

 permit ample scope in the selection of better varieties or in improvement 

 by breeding. In a large collection of D. hispida, much less variation was 

 seen, and progress through breeding seemed to be limited. In Puerto 

 Rico, sufficient variation has not been introduced with respect to D. 

 pentaphylla and D. nummularia to permit selection, but these species 

 are known to be highly variable. 



In the study of only a small number of clones, erroneous impres- 

 sions may be gained concerning the entire species. Each of these species, 

 now little known scientifically, merits careful study before wild and 

 cultivated forms are carelessly destroyed. 



The five minor yam species mentioned here have much in common 

 with other edible species with respect to their growth cycle and re- 

 quirements, but each also differs with respect to small details. All are 

 propagated from pieces of the tuber, but D. pentaphylla, D. dume- 

 torum, and D. nummularia are also propagated from aerial tubers. All 

 can also be propagated from seeds when available. 



All are perennial plants with annually renewed foliage. The tubers 

 are renewed annually and serve only as temporary food reserves used 

 during the growth of the new vine and the new tuber. An exception is 

 D. hispida, the new tuber of which arises from a lobe of the old, and 

 therefore the tuber is perennial. It is also possible that the tuber of D. 

 nummularia is perennial. 



In contrast to other cultivated yams, these minor species are often 

 used as perennials, usually when they are harvested from the wild. 

 However, even when cultivated, they are often left in the soil for 2 or 3 

 years so that large tubers are produced. 



Like all yams, the minor species are adapted to a year-long cycle 



Growth Cycle 



16 



