Performance of new hybrid yam (D. rotundata Poir) varieties in the forest zone of Nigeria

摘要

Four hybrid yam varieties (TDr 89/01438, TDr 89/02665, TDr 95/01924 and TDr 89/01213) and three local cultivars (Danacha, Obiaturugo and 93-2) were evaluated for tuber yield, leaf mosaic virus and nematodes infection at Orin-Ekiti for three years, 1999 to 2001. Varietal differences and relationship between tuber yield, severity of leaf mosaic virus and tuber infection by nematodes were determined. Tuber yields were highest in 89/02665 and 95/01924 with a mean of 16 and 14 t.ha~(-1) respectively. The lowest yielders were Danacha (5 t.ha~(-1) and a hybrid 89/01438 (6.6 t.ha~(-1)). in the two highest yielding varieties, 47 to 53 percent of yields were contributed by ware yam sizes which contributed 34 percent of the total number of tubers harvested.Seven percent of the tubers harvested were of ware sizes in Danacha and they contributed 11 percent to total yield. Reaction to leaf mosaic virus was low in TDr 89/02665, mild in 95/01924, and moderate to severe in 89/01438, 93-2 and Danacha. Nematode attack on tubers was mild in all varieties. Positive correlations were found between tuber yield and percent weight of ware yams (r= 0. 53~(**)) and percent number of ware tubers (r= 0.76~(***)). Correlation was negative and significant between tuber yieldand virus infection (r= -0.59~(***)) whereas it was not significant for nematode infection (r= 0.13). Two hybrid varieties 89/02665 and 95/01924 are recommended for on-farm testing by farmers in forest areas of Nigeria.