Agronomic and hormonal approaches for enhancing flowering intensity in white Guinea yam (Dioscorea rotundata Poir.).

Developing novel white Guinea yam (Dioscorea rotundata) varieties is constrained by the sparse, erratic, and irregular flowering behavior of most genotypes. We tested the effectiveness of nine agronomic and hormonal treatments to enhance flowering on D. rotundata under field conditions. Genotypes responded differently to flower-inducing treatments (p<0.001). Of the test treatments, pruning and silver thiosulfate (STS) were effective in increasing the number of spikes per plant and the flowering intensity on both sparse flowering and monoecious cultivars. STS and tuber removal treatments promoted female flowers on the monoecious variety while pruning and most treatments involving pruning favored male flowers. None of the treatments induced flowering on Danacha, a non-flowering yam landrace. Flower-enhancing treatments had no significant effect on flower fertility translated by the fruit set, since most treatments recorded fruit sets above the species' average crossability rate. Flower-enhancing techniques significantly influenced number of tubers per plant (p = 0.024) and tuber dry matter content (DMC, p = 0.0018) but did not significantly affect plant tuber yield. Nevertheless, treatments that could enhance substantially flowering intensity, such as pruning and STS, reduced tuber yield. DMC had negative associations with all flowering-related traits. This study provided insights into white yam flower induction and suggests promising treatments that can be optimized and used routinely to increase flowering in yam crop, without significantly affecting flower fertility and tuber yield.

Optimization of plant density and fertilizer application to improve biofortified common bean (Phaseolus vulgaris L.) yield on Nitisols of South-Kivu, Eastern D.R. Congo.

Soil nutrient depletion and poor farming practices are serious challenges limiting crop productivity in soils of the eastern Democratic Republic of Congo (D.R. Congo). An experiment was conducted in two cropping seasons to assess the effect of plant density (25 plants m2 and 33 plants m2) and fertilizer application (with and without NPK) on the yield and yield components of three biofortified common bean varieties (HM21-7, RWR2245 and RWR2154). The experiment involved two plant densities, two fertilizer rates and three varieties arranged in a split-split plot design with three replications. Results showed that yield significantly varied with plant density, variety and fertilizer rate (p < 0.05). The best performing variety in terms of grain yield was HM21-7 (1.5 t ha-1) as compared to RWR2154 (1.09 t ha-1) and RWR2245 (1.14 t ha-1). The NPK fertilizer increased the grain yield by 38.2%. Grain yield increased also with the plant density, highest grain yield being recorded on higher plant density (1.37 t ha-1) as compared to low lower plant density (1.25 t ha-1). Agronomic efficiency (AE) was influenced by the variety, with the highest AE obtained on RWR2245 (23.27 kg kg-1) and on high plant density (20.34 kg kg-1). Therefore, we concluded that increasing the plant density by reducing the plant spacing, using NPK fertilizer and high yielding varieties provide with an opportunity to improving common bean yields on Nitisols dominating the highlands of eastern D.R. Congo.

Bioclimatic zonation and potential distribution of Spodoptera frugiperda (Lepidoptera: Noctuidae) in South Kivu Province, DR Congo.

BACKGROUND: The fall Armyworm (FAW) Spodoptera frugiperda (JE Smith), is currently a devastating pest throughout the world due to its dispersal capacity and voracious feeding behaviour on several crops. A MaxEnt species distributions model (SDM) was developed based on collected FAW occurrence and environmental data's. Bioclimatic zones were identified and the potential distribution of FAW in South Kivu, eastern DR Congo, was predicted. RESULTS: Mean annual temperature (bio1), annual rainfall (bio12), temperature seasonality (bio4) and longest dry season duration (llds) mainly affected the FAW potential distribution. The average area under the curve value of the model was 0.827 demonstrating the model efficient accuracy. According to Jackknife test of variable importance, the annual rainfall was found to correspond to the highest gain when used in isolation. FAWs' suitable areas where this pest is likely to be present in South Kivu province are divided into two corridors. The Eastern corridor covering the Eastern areas of Kalehe, Kabare, Walungu, Uvira and Fizi territories and the Western corridor covering the Western areas of Kalehe, Kabare, Walungu and Mwenga. CONCLUSIONS: This research provides important information on the distribution of FAW and bioclimatic zones in South Kivu. Given the rapid spread of the insect and the climatic variability observed in the region that favor its development and dispersal, it would be planned in the future to develop a monitoring system and effective management strategies to limit it spread and crop damage.