Table 2. — Dioscorea rotundata and D. cayenensis characteristics 



and rating system^ 



Number Characteristic observed Rating system Scale and extremes 



1 



Number of stems per plant • • • 



Counted 



1 to many. 



2 



Branching tendency of 



Absence or presence 



l = no, 2 = yes. 





lower stem. 



of branches, 









0.5 meter. 





3 



Anthocyanin content of stem . 



Estimated visually ■ • 



O = none, 5 = 









maximum. 



4 



Amount of wax on lower 



do 



Do. 





stem. 







5 



Quantity of thorns on stems • • 



do 



1 = minimum, 5 = 









maximum. 



6 



Presence of striations on 



do 



1 = minimum, 





stems. 





5 = some. 



7 



Anthocyanin content of 



do 



1== minimum, 





petiole. 





3 = maximum. 



8 



Presence of striations on 



do 



O = none, 3 = 





petiole. 





maximum. 



9 



Length of petiole compared 



Checked by hand • • 



. 1 = less than V2 





to leaf blade. 





blade length. 









2 = longer. 



10 



The extent to which the 



Estimated visually • 



• 1 = little. 





petiole ears encircle the 





3 = much. 





stem. 







11 



Type of leaf 



. J udged by a some- 



1 = deltoid, 2 = 







what linear scale. 



shield, 3 = 









intermediate. 









4 = ovate, short, 









5 = ovate. 









6 = ovate, long. 



12 



Intensity of virus symptoms 



Estimated visually • 



• O = none, 5 = 





of young foliage. 





maximum. 



13 



Anthocyanin content of leaf • 



do 



Do. 



14 



Amount of wax on leaf 



do 



Do. 



15 



Green color intensity of leaf ■ 



do 



■ 1 = very light 









green, 5 — very 









dark green. 



16 



Yellow shading of foliage • • • 



do 



• O==none, 5 — 









maximum. 



17 



Shape of leaf 



■ Judged only with 



1 = ovate, 5 = 







respect to length 



deltoid. 







and width. 





18 



Bluntness of lobes of leaf • • • 



• Estimated visually • 



. 1 = very pointed. 









5 == very blunt. 



19 



Development of an apical 



do 



• 1 = minimum, 5 = 





tail. 





maximum. 



20 



Smoothness of leaf surface • 



do 



• 1 = very rugose. 









5 = very 









smooth. 



21 



Leatheriness of leaf 



. Estimated by feel • 



. l = not leathery, 



5 = very 

 leathery. 



11 



