Potentials of Cultivated Varieties and Wild Yam Seeds as Efficient Alternative Plant Genetic Resources for Resistant Genotypes against Yam Mosaic Virus (YMV) in Togo

In Togo, cultivated yams are severely infected by Yam Mosaic Virus (YMV). In order to find an efficient method for researching genotypes resistant to the virus, this study aims to screen plants obtained from yam seeds. As such, 640 yam seedlings were produced from seeds collected on 20 plants (accessions) of wild yams, D. praehensilis (10) and D. abyssinica (10) and on 12 plants of the complex D. cayenensis-rotundata. The yam seeds were collected during prospections carried out in october 2018, covering 14 districts in Central and Plateaux regions of Togo. Then, 20 yam seedlings (ten plants in two replicates) per accession, were inoculated with YMV isolate M9-30 using mechanical inoculation. Leaf samples taken from the inoculated seedlings, were analyzed by RT-PCR to detect the YMV, using QiAgen one step RT-PCR Kit and a pair of primers YMV1 & YMV2 (196 pb) . Data was analyzed using GenStat 12.1 and SPSS 20.  Following the observations and molecular analyzes, it appears that 46.5% of the seedlings inoculated in D. praehensilis, were resistant, while 27.08% of resistant plants and 0.47% of tolerant plants were obtained in  D. cayenensis-rotundata  complex and 17% resistant plants obtained in D. abyssinica. Statistical analysis showed a significant difference between among accessions of D. praehensilis and those of D. abyssinica at P≤0.05. The high rate of 30% of resistant plants provided in total, and specifically, the results obtained in D. cayenensis-rotundata compared to those provided in 2012 using clonal selection, i.e. 8.33%, suggest that, screening of seedlings from yam seeds, is efficient and could be used for researching yam genotypes resistant to YMV. Results of D. abyssinica and of some accessions of D. cayenensis-rotundata, would be influenced by the proximity of other yam species. The yam seeds production environment would, therefore, be an important factor to take into account.