Evaluation of Musa host plant response using nematode densities and damage indices

Host plant response of seven Musa accessions to Radophlus similis and helicotylenchus multicintus was evaluated at Namulonge, Uganda.Suckers detached from first cycle harvested plants grown in inoculated and not inoculated fields were indexed for root and corm damage. Nematodes were extracted from the indexed roots. Relationship between root damage parameters and nematodes population densities were examined using correlation and principal component analysis. Damage parameters were of major importance. Three groups of cultivars could be statistically differentiated. The cultivars Gros Michel(Musa AAA), Pisang Awak (Musa AAA) and Obino I Ewai (Musa AAB) were more sensitive and susceptible to nematode attack. Cultivar Nabusa (Musa AAA, highland banana clone set Nfuuka) was intermediate and did not differ significantly from either group

East African highland banana production as influenced by nematodes and crop management in Uganda

Production loss caused by nematodes in East African highland banana was evaluated at Sendusu, near Kampala in Uganda, 1120 m above sea level. The commonly grown cultivar, Mbwazirume, was grown in nematode-infested and non-infested plots under heavily mulched, clean-weeded and millet-intercropped management regimes. Influence of the different treatments was evaluated over the second to the fourth crop cycle and management was observed to have the greatestinfluence on production. The non-infested heavily mulched plots produced 16.1 tonnes per ha per cycle compared with the clean-weeded and non-infested millet-intercropped plots only 5.6 and 5.3 tonnes per ha per cycle, respectively. Presence of Radopholus similis and Helicotylenchus multicinctus reduced the average production in the well mulched, clean-weeded and millet-intercropped plots by 30%, 32% and 38%, respectively. The nematode-induced loss is a result of a reduction of bunch weight, a reduction of flower production and an increase in plant toppling. When plant toppling occurred on a mat, the chance was highly reduced that this mat produces a harvestable bunch in the following cycle. Damage by the banana weevil, Cosmopolites sordidus, was higher in nematode-infested plants compared with noninfested plants. Itmay be thatin nematode-infested plants, weevil larvae are more successfulin developing or thatadultweevils prefernematodeinfested plants for egg disposal. No interaction between Black Sigatoka and nematode infestation was observed

Path analysis: a novel approach to determine the contribution of nematode damage to East African highland banana (Musa spp., AAA) yield loss under two crop management practices in Uganda

Damage caused by plant-parasitic nematodes on East Africa Highland banana cultivar Mbwazirume was evaluated at Sendusu, Central Uganda. Banana plots were either nematode-infested or non-infested and received either continuous heavy mulch or were finger millet (Eleusine coracana) inter-cropped. An infestation with banana weevil, Cosmopolites sordidus, occurred naturally. Suckers detached from third crop cycle harvested plants were indexed for root and corm damage. Nematodes were extracted from the indexed roots. Banana weevil damage was observed in a cross-section through the corm of the harvested plant. Relationships between root damage, corm damage and nematode population densities were examined using correlation analyses. Path analysis was used to establish their relative effects on bunch weight. Independent of the type of crop management, percentage root necrosis, percentage dead roots, Radopholus similis and Helicotylenchus multicinctus population densities were each negatively correlated with bunch weight. Banana weevil damage and Pratylenchus goodeyi population densities were not correlated with bunch weight (P≤0.05). Path analysis revealed that root necrosis under heavy mulching and dead roots under finger millet inter-crop were the major factors associated with reduced bunch weight. Independent of the type of crop management, path analysis demonstrated that R. similis and then H. multicinctus contributed most, and to a lesser extent P. goodeyi, to root necrosis and dead roots. C. sordidus damage to the inner or outer corm appeared not to affect bunch weight

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

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

Inheritance of race-nonspecific resistance to Exserohilum turcicum in maize synthetic population OhS10

Progeny tests of resistant lines derived from maize (Zea mays L.) synthetic population OhS10 were conducted at one location during two years (1993-94) in Ohio (Guerne) and at two locations during one year (1993) in Uganda (Kabanyolo and Namulonge) to examine the inheritance of resistance to Exserohilum turcicum(Pass.), causal agent of northern leaf blight (NLB). Individual plants in single ear derived selfed progenies (S1 and S1:2) were inoculated in a controlled fashion (Guerne, Namulonge) or naturally infected (Kabanyolo). Host responses to infection were characterized by determining area under the disease progress curve (AUDPC), calculated from percent leaf area affected (PLAA) and lesion number counts, and lesion size. The majority of S1 and S1:2 progenies had few lesions, low rates of disease development, and high levels of resistance, indicating that multiple factors govern expression of resistance. Of the progenies tested, S20-4, S30-5, S30-6 and S30-7 exhibited consistently high levels of resistance to NLB.Des tests de descendance des lignees resistantes obtenues a partir d'une population synthetique de mais OhS10 ont ete executes a un endroit pendant deux annees (1993-1994) Ohio (Guerne) et a deux endroits pendant une annee (1993) en Ouganda (Kabanyolo et Namulonge) pour examiner la transmission de la resistance a Exserohilum turcicum (Pass.), qui cause le rouille des feuilles (qui sevit au nord) (NLB). Les plantes individuelles des progenies obtenues par descendance autofecondee issue d'un epis unique (S1 et S1:2) etaient inoculees de facon controee (Guerne, Namulonge) ou infectees naturellement (Kabanyolo). Les reponses des infections etaient caracterisees par la determination de la surface en dessous de la courbe de progres de la maladie (AUDPC), qui etaient calculee a partir du pourcentage de surface de la feuille affectee (PLAA) et le nombre des lesions et la taille de lesions. La majoritedes descendants S1 et S1:2 avaient peu de lesions, un developpement ralentie de la maladie et un niveau de resistance eleve, ce qui indique que plusieurs paramtres influencent l'expression de la resistance. S20-4, S30-5, S30-6 et S30-7 montrent un niveau de resistance eleve contre NLB

Inheritance of race-nonspecific resistance to Exserohilum turcicum in maize synthetic population OhS10

(African Crop Science Journal, 1997 5(1): 55-64

Measurement of the field response of Musa genotypes to Radopholus similis and Helicotylenchus multicinctus and the implications for nematode resistance breeding

Crop growth and damage parameters (plant growth and yield, root damage and nematode population densities), believed to be associated with resistance of Musa genotypes to nematodes under field conditions, were evaluated in a field trial of 24 Musa genotypes inoculated at planting with a combination of Radopholus similis and Helicotylenchus multicinctus with the objective to identify parameters with strong association with nematode resistance and high heritability. Correlation and path analysis of the association between plant growth, yield, root damage and nematode population densities showed a strong negative association between percentage dead roots, percentage root necrosis, R. similis and H. multicinctus population densities and yield. The strongest negative association was observed between percentage dead roots and yield. Broad-sense genotype heritability estimates demonstrated that heritability estimates for percentage dead roots, number of large lesions and nematode population density were most affected by inoculation with nematodes. These results indicate therefore that effective selection for nematode resistance under field conditions could be obtained by using an index, that includes percentage dead roots, the number of large lesions, and nematode population density