EFFECTS OF SERIAL PLANTING OF SEED YAM TUBERS ON VIRUS INCIDENCE AND YAM TUBER DEGENERATION

Abstract

Vegetative propagation of yam ( Dioscorea spp.) with seed tubers is done to ensure uniformity of crop growth and yield. The objective of this study was to evaluate the effect of serial planting of seed yam on virus incidence and tuber degeneration in the Southern Guinea Savanna agro-ecologies of Nigeria. This study was conducted during the wet seasons of 2010 to 2012 at Kwara State and Abuja Federal Capital Territory (Abuja-FCT) in Nigeria. TDa 05/00129 and TDr 89/02665 yam bred lines from the International Institute of Tropical Agriculture, Ibadan, and three popular local varieties from each of Kwara State and Abuja Federal Capital Territory (Abuja- FCT) were used in the study. Harvested seed yams were tested for Yam mosaic virus (YMV), Yam mild mottle virus (YMMV), Dioscorea alata bacilliform viruses (DaBV) and Cucumber mosaic virus (CMV). Data obtained for germination percentage, virus incidence and tuber yields were subjected to ANOVA with mean separation done using Tukey HSD method in SPSS version 24. Viruses YMV, YMMV and DaBV were detected in seed yam as single or mixed infections. High virus incidence was associated with low tuber yield while low virus infection was associated with high tuber yield for most yam varieties. However, TDa 05/00129 produced high tuber yield inspite of high incidence of viruses in the tubers, indicating adaptation of this variety. There was progressive increase in virus population in yam seeds from the first to the third year of study with concurrent degeneration of seed yam and low yield at harvest.La multiplication v\ue9g\ue9tative de l\u2019igname (esp\ue8ces de dioscorea ) avec des tubercules de graine est faite pour assurer l\u2019uniformit\ue9 de la croissance de culture et pour rapporter. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019effet de la plantation p\ue9riodique de l\u2019igname de graine sur la d\ue9g\ue9n\ue9rescence d\u2019incidence et de tubercule de virus en agro\ue9cologie du sud de la savane de la Guin\ue9e du Nig\ue9ria. Cette \ue9tude a \ue9t\ue9 entreprise pendant les saisons des pluies de 2010 \ue0 2012 \ue0 l\u2019\ue9tat de Kwara et au territoire capital f\ue9d\ue9ral d\u2019Abuja (Abuja-FCT) au Nig\ue9ria. TDa 05/00129 et TDr 89/02665 igname multipli\ue9e raye de l\u2019institut international de l\u2019agriculture tropicale, Ibadan, et trois vari\ue9t\ue9s locales populaires de chacun de l\u2019\ue9tat de Kwara et du territoire capital f\ue9d\ue9ral d\u2019Abuja (Abuja-FCT) ont \ue9t\ue9 employ\ue9es dans l\u2019\ue9tude. Des ignames moissonn\ue9es de graine ont \ue9t\ue9 examin\ue9es virus pour le virus doux du virus de mosa\uefque d\u2019igname (YMV), virus ignifuge de l\u2019igname (YMMV), les virus bacilliformes de dioscorea alata (DaBV) et de concombre mosa\uefque (CMV). Des donn\ue9es obtenues pour le pourcentage de germination, l\u2019incidence de virus et les rendements de tubercule ont \ue9t\ue9 analys\ue9es utilisant ANOVA avec la m\ue9thode moyenne de Tukey HSD de s\ue9paration dans la version 24 de SPSS. Des virus YMV, YMMV et DaBV ont \ue9t\ue9 d\ue9tect\ue9s en igname de graine en tant qu\u2019infections simples ou m\ue9lang\ue9es. L\u2019incidence \ue9lev\ue9e de virus a \ue9t\ue9 associ\ue9e au bas rendement de tubercule tandis que la basse infection de virus \ue9tait associ\ue9e au rendement \ue9lev\ue9 de tubercule pour la plupart des vari\ue9t\ue9s d\u2019igname. Cependant, TDa 05/00129 a produit le rendement \ue9lev\ue9 de tubercule malgr\ue9 l\u2019incidence \ue9lev\ue9e des virus dans les tubercules, indiquant l\u2019adaptation de cette vari\ue9t\ue9. Il y avait augmentation progressive de population de virus pendant graines d\u2019igname d\ue8s la d\ue9but \ue0 la troisi\ue8me ann\ue9e d\u2019\ue9tude avec la d\ue9g\ue9n\ue9rescence concourante de l\u2019igname de graine et du bas rendement \ue0 la r\ue9colte