Enhancing productivity of farmer-saved seed yam in Ghana: Positive selection and neem leaf powder factors

Recycling of diseased and pests infested seed yam ( Dioscorea spp.) has resulted in drastic yield reductions in yam production. The objective of this study was to determine the effect of positive selection on the quality of farmer-saved seed yam and also evaluate the effect of neem leaf powder in managing plant parasitic nematodes damage to yam. Two farming systems namely; Positive selection (PS) and Farmer practice (FP) and two soil amendment regimes; neem leaf powder at 20 g stand-1 (NA20) and no neem amendment (NA0) were tested on one variety of yam (Dente). A 2 x 2 x 1 factorial study, mounted on a randomised complete block design in a split plot arrangement was conducted in four replications. Positive selection occupied main plots; while Farmer practice occupied sub-plots. The study was conducted in eight communities located in two municipalities of Ghana, during 2015-2017. Parameters evaluated included Yam Mosaic Virus incidence and severity, incidence and severity of nematode cracks and galling on yam tubers, plant establishment and yield of yam. It was observed that Yam Mosaic Virus (YMV) disease incidence decreased from 38% in 2016 to 31% in 2017 in PS plots as a result of using virus-free planting materials. However, in FP plots, it increased from 67% in 2016 to 72% in 2017. Neem leaf powder amendment resulted in significantly (P< 0.05) low tuber galling (7%) compared with 40% in unamended plots. Similarly, PS plots yielded 7.7 t ha-1 compared to 5.9 t ha-1 in FP fields. In conclusion, Positive selection out-yielded FP by 30.5%; while PS-neem leaf powder interaction resulted in 38.5% over and above FP without neem amendment. Le recyclage des semences d'igname ( Dioscorea spp.) contaminées par des maladies et des parasites a entraîné une réduction drastique du rendement de la production d'igname. L'objectif de cette étude était de déterminer l'effet de la sélection positive sur la qualité des semences d'igname conservées par les agriculteurs et également d'évaluer l'effet de la poudre de feuilles de neem dans la gestion des dommages causés par les nématodes parasites des plantes. Deux systèmes agricoles à savoir; Sélection positive (PS) et pratique paysanne (PF) et deux régimes d'amendement du sol; De la poudre de feuille de neem à 20 g du stand-1 (NA20) et aucun amendement de neem (NA0) ont été testés sur une variété d'igname (Dente). Une étude factorielle de 2 x 2 x 1, montée sur une dispositif en blocs aléatoires complets dans un arrangement en