Morphological Assessment and Effectiveness of Indigenous Rhizobia Isolates that Nodulate P. vulgaris in Water Hyacinth Compost Testing Field in Lake Victoria Basin

Abstract

Aims: The study was aimed at isolating, identifying and assessing the effectiveness of indigenous rhizobia nodulating P. vulgaris in Lake Victoria Basin (LVB). Study design: Randomized complete block design. Place and Duration of Study: Soil and nodule samples were collected from Kisumu (Kenya); Kabanyolo (Uganda) and Nyabarongo (Rwanda). Field experiments: Kisumu (Kenya). Lab and greenhouse experiments: Department of Plant and Microbial Sciences Kenyatta University (Kenya) and Makerere University (Uganda). Research was carried out between January 2012 and April 2013. Methodology: Rhizobia were isolated from nodules obtained from P. vulgaris (rose coco variety) plants planted in the LVB water hyacinth compost trial fields and whole soil trapping experiments in the greenhouse using soil obtained from the LVB. The isolates were identified using morphological characteristics. Isolates from each group were used in authentication using the infection technique. Results: One hundred and twenty eight isolates were obtained from the trapping experiments and placed into nine groups based on their morphological characteristics. Four hundred and seventy two isolates were obtained from the nodules of the P. vulgaris grown in soils amended with water hyacinth compost and were placed into sixteen groups. The isolates varied in their morphological characteristics. There was a significant difference in the infectiveness and effectiveness of the representative rhizobia isolates. Conclusion: The studies revealed that rhizobia isolates from Lake Victoria are different morphologically. Authentication experiments, confirmed that the majority of the isolates were rhizobia due to their ability to infect the host plant P. vulgaris. All representative isolates varied in their ability to infect and fix nitrogen. Isolates that are more effective compared to the commercial Rhizobium leguminosarum biovar phaseoli strain 446 were identified in this study. The effective indigenous rhizobia have therefore the potential of being sources of inocula for P. vulgaris.

Potential of Native Rhizobia in Enhancing Nitrogen Fixation and Yields of Climbing Beans (Phaseolus vulgaris L.) in Contrasting Environments of Eastern Kenya

“…The morpho-cultural characteristics of the isolates based on Gram staining results and growth on YEMA-CR and YEMA-BTB media under dark incubation, confirmed the standard morpho-cultural characteristics of Rhizobium species as described by Vincent ( 1970 ), Beck et al ( 1993 ), and Somasegaran and Hoben ( 1994 ). Morphological characteristics of rhizobia which nodulated climbing beans in the present study are similar to those reported by Kawaka et al ( 2014 ) and Muthini et al ( 2014 ). Temperature, pH, and soil salinity are among the abiotic factors that affect morphological characteristics of rhizobia.…”

Genetic Characterization and Diversity of Rhizobium Isolated From Root Nodules of Mid-Altitude Climbing Bean (Phaseolus vulgaris L.) Varieties

“…The nine different morphotypes of rhizobia showed the diverse nature of the isolates colonizing nodules of MAC beans in Eastern Kenya. The results of this study on morphological and biochemical characterization of native rhizobia isolates nodulating common beans corresponded to the findings reported in other recent studies done in Kenya ( Kawaka et al, 2014 ; Muthini et al, 2014 ) and in Ecuador ( Torres-Gutiérrez et al, 2017 ).…”

“…Ten healthy and undamaged root nodules of MAC 13 and MAC 64 climbing beans from each site were selected and used in the isolation of rhizobia following the standard protocols described by Somasegaran and Hoben (1994) . The nodules were washed, surface sterilized in 1% sodium hypochlorite solution for 3 min, rinsed in seven changes of sterile distilled water and then crushed with a sterilized glass rod ( Muthini et al, 2014 ). A loop-full of the resulting suspension was streaked on Yeast extract mannitol agar (YEMA) supplemented with Congo red (0.00125 mg/kg) and incubated in the dark at 28°C for 3–5 days ( Vincent, 1970 ).…”

“…Using the standard microbiological techniques described by Somasegaran and Hoben (1994) , all the isolates were characterized for selected morphological parameters such as colony size, shape, border, elevation, color, mucosity, transparency, and capacity to produce the exopolysaccharide gum ( Liu, 2014 ; Muthini et al, 2014 ). Other tests that were carried out included Gram staining where young pure isolates (3–4 days old) cultured on YEMA were smeared on clean microscope slides.…”

Isolation and Characterization of Nitrogen Fixing Rhizobia from Cultivated and Uncultivated Soils of Northern Tanzania

“…This means that the native rhizobia in the control were competitive and effective in fixing nitrogen to meet the host nitrogen requirements level thus there were no need to use new inoculants at such field [163]. The study conducted by Maingi [164] in Kenya revealed that most isolates were rhizobia with different morphology, the isolated strain 446 was more effective in fixing nitrogen compared with Rhizobium leguminosarum biovar phaseoli and the nodulated legume plants had the highest shoot dry weight than the non nodulated plants. All rhizobia strains isolated from Amazon soils during the study for evaluating plant growth-promoting traits of Rhizobium strains for their co-inoculation in common beans (Phaseolus vulgaris) were found to fix nitrogen efficiently as free living bacteria [165].Weaver and Frederick [166] reported that there were no increase in yield even when there were less than 1.1 × 10 1 native rhizobia per g of soil regardless of majority nodules being formed by inoculum strain.…”