Effect of using virus-free cutting on growth, yield and appearence quality of tuber in sweet potatoes (Ipomea batatas Lam.) and the duration period of these effect

bouture calidad crecimiento croissance crop yield cuttings duration esquejes growth ipomoea batatas plant condition plantas libres de virus plante indemne de virus profitability quality rendement des cultures rendimiento de cultivos rentabilidad tubercule tubers