Optimum sample size for Pratylenchus goodeyi (Cobb) Sher and Allen density and damage assessment in highland banana (Musa AAA) in Uganda

The optimum sample size for assessment of nematode densities and related damage in East African highland banana was estimated at Kikoni parish in Ntungamo district, Uganda. Kikoni parish is at an elevation ranging from 1360 to 1480 meters above sea level and the East African highland banana (Musa AAA, Matoke and Mbidde groups) is the dominant crop. The parish is approximately 10 km2 in size, with an estimated total of 500 farms. Out of these farms, 24 were randomly selected and a minimum of 15 plants per farm were sampled. Root samples were collected from recently flowered plants, assessed for root damage and nematodes were extracted from the scored root segments. Hierarchical classification analysis was performed on the values for density and damage to calculate the coefficient of variation and the method of maximum curvature was used to determine the optimum number of farms in the parish and number of banana plants within each farm for nematode density and damage assessment. Pratylenchus goodeyi was the dominant species with densities ranging from 500 to 25,000 per 100g fresh root weight, while the percentage dead roots ranged from 0.8% to 14.0% and the percentage root necrosis from 1.1% to 17.1%. The optimum numbers established, were three farms within the parish and five recently flowered banana plants in each farm.La grandeur optimale de l'\ue9chantillon pour \ue9valuer les densit\ue9s des n\ue9matodes et les d\ue9g\ue2ts qui y sont li\ue9s sur les bananes en hautes terres de l'Afrique de l'Est a \ue9t\ue9 estim\ue9e en Uganda dans la localit\ue9 de Kikoni, Ntungamo district, situ\ue9e entre 1360 et 1480 m d'altitude. La culture la plus dominante dans cette localit\ue9 est la banane comprenant les groupes de Musa AAA, Matoke et Mbidde. Kikoni a une grandeur de 10 km2 avec un nombre total d'environs 500 fermes. De ceci, 24 fermes ont \ue9t\ue9 s\ue9lectionn\ue9es au hasard et 15 plants \ue9chantillon\ue9s par ferme. Les \ue9chantillons des racines ont \ue9t\ue9 collectionn\ue9s des plants en floraison, \ue9valu\ue9s pour les d\ue9g\ue2ts sur les racines; et les n\ue9matodes ont \ue9t\ue9 extraits \ue0 partir des fragments des racines \ue9valu\ue9s. L'analyse hi\ue9rarchique de classification a \ue9t\ue9 perform\ue9e sur les valeurs pour la densit\ue9 et les d\ue9g\ue2ts afin de calculer le coefficient de corr\ue9lation. La m\ue9thode de courbure maximale a \ue9t\ue9 utilis\ue9e pour d\ue9terminer le nombre optimum de fermes dans la localit\ue9 et les plants des bananiers dans chaque ferme pour l'evaluation de la densit\ue9 des n\ue9matodes et les d\ue9g\ue2ts. Pratylenchus goodeyi \ue9tait l'esp\ue8ce dominante avec densit\ue9s allant de 500 \ue0 25000 par 100 g de poids frais des racines, pendant que le pourcentage des racines mortes variat de 0.8 \ue0 14.0 % et le pourcentage des racines n\ue9cros\ue9es de 1.1 \ue0 17.1 %. Le nombre optimun \ue9tabli \ue9tait de 3 fermes dans la localit\ue9 et 5 plants de bananiers en floraison dans chaque ferme