Table 2.

Viral disease incidence and severity scores recorded in four agro-ecological zones and five yam species, during two surveys conducted in Cameroon in 2014 and 2016

Agro-ecological zone	Yam species	Plants examined	Mean incidence (%)	Mean severity	Associated symptoms
Zone II: high guinea savannah	D. alata	41	9.4	3	M, Lb, Ld, Sh, St
	D. bulbifera	5	0	0	–
	D. cayenensis	24	41.2	2.9	M, Mo, Ld, Sh, St
	D. dumetorum	1	0	0	–
	D. rotundata	859	15.5	2.4	M, Mo, Cu, Lb, Ld, Sh, St, Vb
	Total	930	16.5	2.5
Zone III: western highlands	D. alata	62	3.8	2	M, Mo, Ld, Sh
	D. bulbifera	11	4.6	3	M, Ld
	D. cayenensis	541	65.1	3	M, Mo, Cu, Lb, Ld, Sh, Vb
	D. dumetorum	112	3.8	2	M, Ld, Ln
	D. rotundata	204	32.2	2.5	M, Mo, Cu, Lb, Ld, Sh, St, Vb
	Total	930	43.6	3
Zone IV: humid forest with monomodal rainfall	D. alata	114	13.6	2.1	M, Mo, Ld, St
	D. bulbifera	0	0	0	–
	D. cayenensis	9	50.0	3.3	M, Mo, Ld, St
	D. dumetorum	172	5.0	2.3	M, Ld, St
	D. rotundata	635	37.8	2.6	M, Mo, Lb, Ld, Sh, St
	Total	930	28.2	2.6
Zone V: humid forest with bimodal rainfall	D. alata	103	16.1	2.9	M, Mo, Ld
	D. bulbifera	0	0	0	–
	D. cayenensis	292	53.4	2.7	M, Mo, Cu, Lb, Ld, Sh, Vb
	D. dumetorum	23	00	0	Ld
	D. rotundata	512	18.3	2.4	M, Mo, Cu, Lb, Ld, Sh, Vb
	Total	930	26.8	2.6
Totals by species	D. alata	320	11.2	2.4	M, Mo, Lb, Ld, St
	D. bulbifera	16	4.6	3	M, Ld
	D. cayenensis	866	61.1	2.9	M, Mo, Cu, Lb, Ld, Sh, St, Vb
	D. dumetorum	308	3.6	2.2	M, Ld, St
	D. rotundata	2210	23.7	2.5	M, Mo, Cu, Lb, Ld, Sh, St, Vb
Overall		3720	28.8	2.7

Yam viral disease symptoms: M = Mosaic, Mo = Mottling, Cu = Curling, Lb = Leaf bleaching, Ld = Leaf distortion, Sh = Shoe-stringing, St = Stunting, Vb = Vein-banding