ADAPTATION OF INTRODUCED MUNGBEAN GENOTYPES IN UGANDA

Mungbean ( Vigna radiata (L.) Wilczek) is an important source of nutrients and income for smallholder farmers in East Africa. Mungbean production in countries like Uganda largely depends on landraces, in the absence of improved varieties. In order to enhance productivity, efforts have been underway to develop and evaluate mungbean varieties that meet farmers’ needs in various parts of the country. This study was conducted at six locations in Uganda, to determine the adaptability of introduced mungbean genotypes, and identify mungbean production mega-environments in Uganda. Eleven genotypes (Filsan, Sunshine, Blackgram, Mauritius1, VC6148 (50-12), VC6173 (B-10),Yellowmungo, KPS1, VC6137(B-14),VC6372(45-60),VC6153(B-20P) and one local check were evaluated in six locations during 2013 and 2014. The locations were; National Semi Arid Resources Research Institute (NaSARRI), Abi Zonal Agricultural Research and Development Institute (AbiZARDI),Kaberamaido variety trial center, Kumi variety trial center, Nabuin Zonal Agricultural Research and Development Institute (NabuinZARDI), and Ngetta Zonal Agricultural Research and Development Institute (NgettaZARDI). G × E interactions were significant for grain yield. Through GGEBiplot analysis, three introduced genotypes (Filsan, Blackgram and Sunshine) were found to be stable and high yielding, and therefore, were recommended for release. The six test multi-locations were grouped into two candidate mega-environments for mungbean production (one comprising of AbiZARDI and Kaberamaido and the other comprising of NaSARRI, NabuinZARDI, Kumi, and NgettaZARDI). National Semi Arid Resources Research Institute (NaSARRI) was the most suitable environment in terms of both discriminative ability and representativeness and therefore can be used for selection of widely adaptable genotypes.

HERITABILITY FOR RESISTANCE TO ROSETTE DISEASE IN EXOTIC VALENCIA GROUNDNUTS

Groundnut rosette disease (GRD) is the most destructive virus disease of Valencia groundnuts ( Arachis hypogaea L.) in sub-Saharan Africa. Cultural, biological and chemical control measures have received limited success due to small scale farmers’ inability to use them. Use of host plant resistance provides the most effective and economically viable management option for the resource poor farmers. This study was conducted to determine heritability for resistance to GRD in Valencia groundnuts. Six crosses; Valencia C (P1) × ICGV-SM 90704 (P2), Valencia C (P1) × ICGV-SM 96801(P2), Valencia C (P1) × ICGV-SM 99566 (P2), NuMex-M3 (P1) × ICGV-SM 90704 (P2), NuMex-M3 × ICGV-SM 96801 (P2), and NuMex-M3 (P1) × ICGV-SM 99566 (P2), were made to generate F1, F2, BC1P1 and BC1P2 populations. Data on GRD severity were collected on a 1-9 score scale. Genetic Advance as a percentage of the mean (GAM) and heritability were estimated using variance components. Phenotypic Coefficient of Variation (PCV) and Genotypic Coefficient of Variation (GCV) estimates were high (20.04-70.1%) in the six crosses, except for Valencia C × ICGV-SM 96801(18.1%) and NuMex-M3 × ICGV-SM 96801(17.1%), which exhibited moderate GCV values. Broad and narrow sense heritability estimates for GRD disease score ranged from 64.1 to 73.7% and 31 to 41.9%, respectively, in all the crosses. GAM was high in all the crosses (21-50.7%), except for Valencia C x ICGV-SM 96801 (14.67), M3 x ICGV-SM 99566 (18%) and NuMex-M3 x ICGV-SM 96801 (13.5%) crosses that exhibited moderate GAM. The study revealed the presence of variability of GRD resistance, implying that genetic improvement of these exotic materials is possible.

Identification de caractéristiques agronomiques pour le diagnostic et la prise de décision de régénération des vergers de cacaoyers en Côte d’Ivoire

The rehabilitation of the old cocoa ( Theobroma cacao L. ) farms is one of the major challenges for a sustainable cocoa production. A study was carried out to set up a guide which could be used as a decision making tool for a quick and efficient diagnosis of the old cocoa orchards and to choose the appropriate regeneration option (rehabilitation or replanting). A sample of 90 rehabilitated cocoa farms and of 75 replanted cocoa farms was surveyed in 12 regions representing the three main cocoa producing sectors in the country. Data were collected on the key agronomic characteristics of these cacao farms. These were cocoa variety, farm size, age, yield, planting density, number of shade trees and the level of damages caused by insects and diseases. The results showed that age, planting density and yield were the discriminating criteria of these farms. The average values of these criteria were 25 to 30 years for the age, 800 to 1 000 trees ha-1 for the planting density and 250 to 400 kg ha-1 an-1 for the yield. Based on these criteria and their average values, a decision making guide was designed for the diagnosis of cocoa farms and the choice of regeneration option. According to this guide, old cocoa farms (more than 25 years), degraded and unproductive should be replanted. However, younger farms having planting density and yield higher than the average values above should be rehabilitated.

EFFECT OF TEMPORARY DROUGHT AT DIFFERENT GROWTH STAGES ON SNAP BEAN POD QUALITY AND YIELD

High quality snap bean ( Phaseolus vulgaris L. ) can be produced under rain-fed conditions, provided that adequate moisture is available. However, drought may occur at any stage of growth of snap bean. The objective of this study was to evaluate the effect of drought stress at different growth stages on pod physical quality and nutrient concentrations. An experiment was conducted at the Horticulture Greenhouse, Hawassa University in Ethiopia. Drought stress (50% of field capacity [FC]) was applied at the unfolding of the fourth trifoliate leaf, flowering and pod formation, against a control with no drought stress. The drought stress treatments and eight cultivars were arranged as a factorial experiment in a completely randomised design, with three replications. Drought stress (50% FC) during reproductive stages significantly (P<0.05) reduced pod texture, appearance, and pod curvature. Drought stress increased protein and zinc concentrations by 41 and 15%, respectively; but reduced iron concentration by 15% in snap bean pods. All the tested cultivars had relatively similar responses to drought stress.