Genetic diversity among farmer-preferred cassava landraces in Uganda

Understanding of genetic diversity among a breeding population is an important requirement for crop improvement as it allows for the selection of diverse parental combinations and formation of heterotic pools for genetic gain. This study was carried out to determine genetic diversity within and among 51 farmer-preferred cassava ( Manihot esculenta ) landraces and 15 elite accessions grown in Uganda. Twenty six simple sequence repeat (SSR) markers used for genetic diversity assessment in this study revealed a total of 154 alleles, of which 24% were unique alleles present only in landraces. The genetic diversity and observed herozygosity in landraces were slightly higher than in elite accessions. Elite accessions clustered with some of the landraces indicating that there were some alleles in common. However, 58.8% of the landraces fell into 3 different clusters independent of the elite accessions. Including these landraces with unique alleles in cassava breeding schemes will increase the chances of producing farmer preferred adapted elite cultivars. The study also revealed genetic differentiation among accessions from different regions providing an opportunity for establishment of heterotic pools within a breeding programme.La compr\ue9hension de la diversit\ue9 g\ue9n\ue9tique est une condition importante dans la s\ue9lection de diverses combinaisons parentales et la formation des groupes h\ue9terotiques d\u2019int\ue9r\ueat g\ue9n\ue9tique pour l\u2019am\ue9lioration des cultures. Cette \ue9tude \ue9tait conduite pour d\ue9terminer la diversit\ue9 g\ue9n\ue9tique parmi 51 vari\ue9t\ue9s locales de manioc ( Manihot esculenta ) pr\ue9f\ue9r\ue9es des fermiers et 15 accessions \ue9lites cultiv\ue9es en Ouganda. Vingt six marqueurs simples \ue0 sequence r\ue9p\ue9t\ue9e (SSR) utilis\ue9s pour l\u2019\ue9valuation de la diversit\ue9 g\ue9n\ue9tique ont r\ue9v\ue9l\ue9 un total de 154 all\ue8les, parmi lesquelles 24% \ue9taient des all\ue8les uniques pr\ue9sentes dans les races locales seulement. La diversit\ue9 g\ue9n\ue9tique et l\u2019h\ue9terozygosit\ue9 observ\ue9es dans les races locales \ue9taient l\ue9g\ue8rement sup\ue9rieures que dans les accessions \ue9lites. Celles-ci s\u2019\ue9taient regroup\ue9es avec quelques vari\ue9t\ue9s locales indiquant donc qu\u2019elles avaient quelques all\ue8les en commun. Par ailleurs, 58.8% des races locales ont form\ue9 trois diff\ue9rents groupes ind\ue9pendamment des accessions \ue9lites. Inclure ces races locales \ue0 all\ue8les uniques dans les syst\ue8mes d\u2019am\ue9lioration du manioc permettra d\u2019augmenter les chances de produire des cultivars \ue9lites pr\ue9f\ue9r\ue9s des fermiers. L\u2019\ue9tude montre aussi que la diff\ue9renciation g\ue9n\ue9tique trouv\ue9e parmi les accessions de diff\ue9rentes r\ue9gions est une opportunit\ue9 offerte pour l\u2019\ue9tablissement des groupes h\ue9terotiques dans le programme d\u2019am\ue9lioration

Genotype identification for intercropping systems : summary

Meeting: Symposium on Intercropping in Semi-Arid Areas, 2d, 4-7 Aug. 1980, Morogoro, TZIn IDL-391

Effects of Mulching Materials on the Growth, Development and Yield of White Yam

Two similar experiments are described in which the effects of different mulching material and staking on the growth, development and yield of white yam ( Dioscorea rotundata ) Minisetts were studied. One white yam cultivar TDR 131 was used and the treatments were: black and white embossed polyethylene plastic (Visqeen 38 mu) with either black or white surface up; light weight black polyethylene plastic, rise straw; staking but no mulch, and no staking and no mulch. Each experiment was laid out in a randomized complete block design with four replications. Polyethylene plastic mulch with white surface up was superior to all other treatments. Total dry matter per plant and total fresh tuber yield were all consistently higher in plants grown under the white surface polyethylene plastic mulch. in 1985, mean tuber size was more than 34% larger than in the traditional staking system and nearly double the value obtained with no staking no mulch treatment. In 1986, mean tuber size was again larger with white surface plastic mulch but not significantly different from those of the staking and rice straw treatments. Plants in all treatments attained peak leaf area index (LAI) about 100 days after planting and those in the white surface plastic mulch maintained a higher LAI for most of the growing season. White surface polyethylene plastic mulch gave the larger Leaf Area Index and Greater Leaf Area Duration which ensure a high bulking rate over a comparatively longer period. It is suggested that under tropical conditions, farmers would obtain better seed yam yields through the use of white surface polyethylene plastic mulch

Studies on mixtures of maize and beans with particular emphasis on the time of planting beans

Meeting: Symposium on Intercropping for Semi-Arid Areas, 10-12 May 1976, Morogoro, TZIn IDL-196

Effects of Mulching Materials on the Growth, Development and Yield of White Yam

Two similar experiments are described in which the effects of different mulching material and staking on the growth, development and yield of white yam ( Dioscorea rotundata ) Minisetts were studied. One white yam cultivar TDR 131 was used and the treatments were: black and white embossed polyethylene plastic (Visqeen 38 mu) with either black or white surface up; light weight black polyethylene plastic, rise straw; staking but no mulch, and no staking and no mulch. Each experiment was laid out in a randomized complete block design with four replications. Polyethylene plastic mulch with white surface up was superior to all other treatments. Total dry matter per plant and total fresh tuber yield were all consistently higher in plants grown under the white surface polyethylene plastic mulch. in 1985, mean tuber size was more than 34% larger than in the traditional staking system and nearly double the value obtained with no staking no mulch treatment. In 1986, mean tuber size was again larger with white surface plastic mulch but not significantly different from those of the staking and rice straw treatments. Plants in all treatments attained peak leaf area index (LAI) about 100 days after planting and those in the white surface plastic mulch maintained a higher LAI for most of the growing season. White surface polyethylene plastic mulch gave the larger Leaf Area Index and Greater Leaf Area Duration which ensure a high bulking rate over a comparatively longer period. It is suggested that under tropical conditions, farmers would obtain better seed yam yields through the use of white surface polyethylene plastic mulch

Effets du type de paillis et de la densité de plantation sur la croissance, le développement et le rendement de mini-semenceaux d'igname guinée

Dans IDL-1152

Control of Digitaria abyssinica (A.Rich) Stapf. with Glyphosate

Investigated were conducted in Uganda on the effect of glyphosate dose rate, timing of application, and the combination of glyphosate with cultural methods for the control of Digitaria abyssinica (A.Rich) Stapf. Results showed a dose rate of 1.5 kg a.e.ha-1 to be optimum. Application with pre-plant tillage did not increase D. abyssinica control, but increased populations of other weeds and costs. Glyphosate efficacy was increased when preceded by slashing, burning or digging. At least one month was required between the cultural pre-treatments and spraying to allow new shoots to emerge. Glyphosate was most effective when applied to D. abyssinica shoots up to eight weeks after emergence. The optimum timing for spraying was between one and two month after cultural pre-treatment. Glyphosate applications considerably reduced labour requirement for preparation of D. abyssinica infested land

Effect of Spacing, Stage and Method of Desuckering on Bunch Size and Yield of Banana Cultivar Kibuzi(AAA-EA)

Two experiments using banana (Musa sp.) cultivar Kibuzi were established to determine the effect of plant spacing, height of suckers at removal and method of desuckering on growth, bunch weight and yield. In the first experiment, cultivar Kibuzi was planted at recommended spacing of 3 x 3 m. Two suckers per stool were maintained and extra suckers were removed at heights of 300 mm, 500 mm and 1000 mm by digging them out or cutting the suckers at soil level. In the second experiment, cultivar Kibuzi was planted at spacings of 2.5 x 2.5, 3 x 3 and 3.75 x 3.75 cm giving plant populations of 1600, 1111 and 711 stools ha-1, respectively. Plant height, pseudostem girth, both at 50 and 100 cm, and total number of standing leaves were significantly (P< 0.05) increased by desuckering at 300 mm while the method of desuckering had no significant effect on these growth parameters. Yield parameters were also significantly (P<0.05) influenced by stage of desuckering. The results also indicated that plant spacing and number of suckers retained per stool have no significant effect on height and pseudostem girth of the plant crop of bananas.Deux essais utilisant le cultivar Kibuzi ont \ue9t\ue9 \ue9tablis pour d\ue9ferminer l\u2019effect de l\u2019espacement, la hauteur des rejets \ue0 l\u2019enl\ue8vement et la m\ue9thode de dedrageonnage sur la croissance, le poid/taille du r\ue9gime et le rendement. Dans le premier essai, le cultivar Kibuzi a \ue9t\ue9 plant\ue9 \ue0 l\u2019espacement recommend\ue9 de 3 x 3 m. Deux rejets par poquet ont \ue9t\ue9 maintenus et des rejets suppl\ue9mentaires ont \ue9t\ue9 enl\ue9v\ue9s \ue0 la hauteur de 300 mm, 500 mm et 1000 mm en deterrant au niveau du sol. Dans le deuxi\ue8me essai le cultivar Kibuzi a \ue9t\ue9 plant\ue9 aux espacements de 2.5 x 2.5; 3 x 3 et 3.75 x 3 cm donnant des populations de 1600, 1111 et 711 poquets ha-1 respectivement. Les r\ue9sultats indiquent que la hauteur de la plante, l\u2019\ue9paisseur de pseudo-tige, les deux \ue0 50 et 100 cm, et le nombre total de feuilles ont augment\ue9 significativement (P<0,05) par le deterage \ue0 300 mm pendant que la m\ue9thode de d\ue9terrement n\u2019a pas eu d\u2019effect significatif sur ces param\ue8tres de croissance. Les param\ue8tres du rendement n\u2019ont pas \ue9t\ue9 influenc\ue9s significativement (P<0,05) par le stade de d\ue9terrement. Les r\ue9sults indiquent aussi que l\u2019espacement des plantes et le nombre de rejets maintenus par poquet n\u2019ont pas eu d\u2019effect significatif sur la hauteur et l\u2019\ue9paisseur de la pseudo-tige des plants de banane

Multilocational Evaluation of Selected Local and Improved Cowpea Lines in Uganda

Six improved cowpea ( ) genotypes intitially selected from International Institute of Tropical Agriculture collection were evaluated for 3 seasons at 4 locations in Uganda, with the objective of comparing their yield performance and assessing their adaptability under Ugandan conditions. The cowpea genotypes were MU-93, TVX 337-025(B), IT90K-109(B), KVU-12349, IT82D-516-2, and IT85F-2841. Across locations and seasons, MU-93 produced highest grain yield (1586 kg ha -1) while KVU-12349 produced the lowest grain yield (505 kg ha-1). At different locations the genotypes&apos; performance varied, whereby IT85F-2841 (1378 kg ha-1), MU-93 (1208 kg/ha), MU-93 (1235 kg ha-1) and IT90K-190 (B) (2373 kg/ha) produced the highest grain yields in Kabanyolo, Pallisa, Kumim and Kaberamaido, respectively. The Additive Main effects and Multiplicative Interaction (AMMI) model was used in the genotype by environment (GXE) analysis to determine the yield and stability of the genotypes in the multi-environment trial. The effect of environments, genotypes and GXE were highly significant (P<0.001). The biplot revealed that the varieties; IT85F-2841 (G1), IT90K-109(B) (G2), IT82D-516-2 (G3), TVX 337-025(B) (G4) and MU-93 (G6) were generally high yielding since AMMI placed them on the right hand side of the mid point of the axis representing the grand mean, Ebelat (G5), Icirikukwai (G7) and KVU-12349 (G8) were generally low yielding and were placed on the left hand side of the midpoint on biplot. IT90K-109(B) (G2) and Icirikukwai (G7) had the highest principal component analysis (IPCA) scores (15.4 and -22.7, respectively) therefore were considered as unstable genotypes. Genotypes IT85F-2841, MU-93, IT82D-516-2, KVU-12349 and Ebelat had moderate IPCA 1 scores; hence moderately stable. TVX337-025(B) had a low IPCA 1 score and thus was relatively a stable genotype. Within environments AMMI and unadjusted means ranked genotypes differently. However, at one location in 2003, 6 out of 8 genotypes were ranked similarly by both estimates. While AMMI alone ranked MU-93 is superior in 6 out of 12 environments. MU-93 has now been recommended for official release inn Uganda

Influence of NPK Fertiliser on Populations of the Whitefly Vector and Incidence of Cassava Mosaic Virus Disease

The influence of NPK fertiliser on the symptoms and spread of cassava mosaic virus disease (CMD) and on populations of the whitefly vector ( Bemisia tabaci ) was investigated in Uganda using three cassava varieties: Migyera (CMD-resistant), Nase 2 (tolerant) and Ebwanatereka (highly susceptible) in 1995-96 and 1996-97 planting seasons. In each season NPK fertiliser significantly (P<0.05) increased the incidence of CMD and led to earlier infection and spread of the disease for varieties Migyera and Nase 2 than in unfertilised control plots, whereas for variety Ebwanatereka no significant differences in infection and disease spread were observed for the control and plots that received NPK application. Adult whitefly populations per shoot were increased significantly (P<0.05) by NPK fertiliser on Nase 2 and Ebwanatereka in 1995-96 and on Ebwanatereka in 1996-97, although the increases were not significantly different. Application of NPK fertiliser did not significantly influence the population of whiteflies on variety Migyera in either experiment. Similarly, NPK fertiliser application did not influence CMD symptom severity for all varieties in either season. These results indicate that NPK fertiliser application is not satisfactory strategy for facilitating the control of CMD.L&apos;influence de l&apos;engrais NPK sur le symptôme et la progression de la mosaïque du manioc (CMD) et sur la population de Bemisia tabaci était evaluee en Ouganda utilisant trois variétés du manioc: Migyera (résistant au CMD), Nase 2 (tolérant) et Ebwanatereka (tres susceptible) pour les saisons pluviales 1995-96 et 1996-97. Dans chaque saison l&apos;engrais NPK a augmenté significativement l&apos;incidence du CMD et a conduit a une infection précose et une progression de la maladie sur les variétés Migyera et Nase 2 comparées aux terrains no-traites par l&apos;engrais. Par contre, Ebwanatereka n&apos;a pas montré des différences significatives en terme d&apos;infection et de progression comparé aux parcelles no-traitées et traitées. La population de Bemisia tabaci par rejet était significativement augmentée (P<0.05) par l&apos;engrais NPK sur Nase 2 et Ebwanatereka en 1995-96 et sur Ebwanatereka en 1996-97, même si les augmentations n&apos;ont pas été significativement différentes. L&apos;application de l&apos;engrais NPK n&apos;a pas influencé significativement la population de Bemisia tabaci sur la variété Migyera dans les différentes expériences. De faÇcon similaire, l&apos;application de l&apos;engrais NPK n&apos;a pas influencé la sévérité du symptôme de CMD pour toutes les variétés pour les différentes saisons. Ces résultats indiquent que l&apos;application de l&apos; engrais NPK n&apos;est pas une stratégies satisfaisante pour le contrôle du CMD