Phenotypic and yield responses of common bean (Phaseolus vulgaris l.) varieties to different soil moisture levels.

BACKGROUND: Morphological plasticity is one of the capacities of plants to modify their morphological appearance in response to external stimuli. A plant's morphology and physiology are constantly tuned to its variable surroundings by complex interactions between environmental stimuli and internal signals. In most of plant species,, such phenotypic and physiological expression varies among different varieties based on their levels of particular environmental stress conditions. However, the morphological and yield responses of common bean varieties to different environmental conditions are not well known. The purpose of the study was to evaluate morphological and yield response of common bean to soil moisture stress and to investigate the morphological mechanism by which common bean varieties tolerate fluctuations in moisture stress. METHODS: A pot experiment was carried out to investigate the effects of different moisture levels on the phenotypic and yield responses of common bean varieties. A factorial combination of five common bean varieties (Hirna, kufanzik, Awash-1, Ado, and Chercher) and three moisture levels (control, waterlogging stress, and moisture deficit stress) was used in three replications. Moisture stress treatments were started 20 days after planting, at the trifoliate growth stage. To evaluate the response of each variety, morphological and yield data were collected at week intervals. MAIN RESULTS: The results indicated that moisture levels and varieties had a significant influence on all growth parameters. Crop phenology was significantly influenced by the interaction effect of moisture level and variety. Exposing Hirna variety to moisture stress led to extended flowering and pod setting by 23 and 24 days, respectively, compared to the other treatments. The results showed that the phenotypic responses to moisture deficit and waterlogging stress varied between varieties. Waterlogging stress had a stronger reduction effect on the fresh weight, dry weight and leaf area of common bean varieties than moisture deficit and the control. Pods per plant, seeds per plant, grain yield per plant, and harvest index were significantly influenced by the varieties, moisture stress levels and their interaction. Except for Chercher and Hirna. However, varieties Ado, kufanzik and Awasha-1 did not show significant differences on the time of flower initiation due to moisture level. Biomass and growth in leaf fresh weight, leaf dry weight, leaf area, leaf number and plant height were significantly influenced by moisture level. When moisture deficit and waterlogging stress occurred, Ado and Awash-1 were more responsive to moisture stress than Hirna, Chercher, and Kufanzik. CONCLUSION: Hence, Hirna and Kufanzik varieties were found to be tolerant because they produced higher yields than the Chercher, Awash-1, and Ado varieties.

Intercropping and Rhizobium Inoculation Affected Microclimate and Performance of Common Bean (Phaseolus vulgaris L.) Varieties.

A field experiment was carried out at Hawassa, during the 2020 cropping season with the objective to evaluate the impact of maize-common bean intercropping and Rhizobium inoculation on microclimate, growth, and yield of common bean varieties. Treatments consisting of two common bean varieties, two levels of inoculation and three spatial arrangements of common bean with another sole maize were laid out in a factorial arrangement in a randomized complete block design (RCBD) with three replications. The results revealed that the main effect of spatial arrangements highly significantly (P < 0.001) affected soil and leaf temperature. Soil moisture content was improved under intercropped plots compared with sole cropping. The intensity of light and qualities, such as red, far-red, and photosynthetically active radiations (µmol m-2 s-1) and ultraviolet rays (UV)-A, UV-B (W m-2), were reduced under intercropping as compared to the sole. Interaction effects of variety, spatial arrangements, and inoculation significantly (P < 0.01) affected plant height and leaf area index. Inoculated sole Nassir outperformed for plant height and leaf area index. Inoculated sole Hawassa Dume variety performed best for nodule number plant-1, nodule dry weight plant-1, pods number plant-1, 100 seed weight, grain yield, and above-ground biomass yield. The highest grain yield (2.8 t ha-1) was recorded from inoculated sole Hawassa Dume. However, considering the equivalent ratio (LER), intercropping with one maize row to two haricot bean rows spatial arrangements was productive by 62% more than sole cropping (total land equivalent ratio of 1.62%).