Evaluation of Bradyrhizobium strains for lupins in Finnish conditions

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Title: Evaluation of Bradyrhizobium strains for lupins in Finnish conditions
Author: Karim, Abdul
Other contributor: Helsingin yliopisto, Maatalous-metsätieteellinen tiedekunta, Maataloustieteiden laitos
University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences
Helsingfors universitet, Agrikultur- och forstvetenskapliga fakulteten, Institutionen för lantsbruksvetenskaper
Publisher: Helsingfors universitet
Date: 2013
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-201507212087
Thesis level: master's thesis
Discipline: Växtproduktionsvetenskap
Plant Production Science
Abstract: Four different Bradyrhizobium sp. (lupin) inoculants were investigated in both greenhouse and field experiments to compare their effects on growth, yield and biological nitrogen fixation. Narrow-leafed and white lupin of the greenhouse experiment compared the strains test in different potting media in a controlled environment, while field experiment tested their performance in field conditions. The greenhouse experiment was conducted with 3 narrow-leafed lupin cultivars (Haags Blaue, Boruta and Sonet) and 1 white lupin cultivar (Ludic). Plants were grown in 3 different potting media (soil, 2 peat : 1 sand and 1 peat : 2 sand) with 5 Bradyrhizobium treatments (uninoculated control, commercial peat inoculant of HAMBI 3118 and liquid cultures of HAMBI 3115, HAMBI 3116 and HAMBI 3118). Plants were grown in a greenhouse unit with average day and night temperature of 22°C and 18°C. Plants were illuminated by using cool white fluorescent tubes maintaining 18 hours day and 6 hours night. In the greenhouse experiment, inoculation significantly increased shoot (117.1-141.9%), root (45.8-64.4%) and nodule (237.0-266.6%) dry weight, plant height (38.3-46%), nodule number (620-659%) and chlorophyll content (29.0-38.5%) over the values found in uninoculated controls. Soil type or potting medium also influenced lupin growth and yield, with better results observed in soil, poorer in 2 peat : 1 sand and poorest in 1 peat : 2 sand. Best performaces were obtaind by inoculating with HAMBI 3115 strain in soil. Uninoculated plants and even inoculated plants grown in peat-sand potting medium, showed relatively poor results, which was more obvious in high-yielding cultivars, Boruta and Ludic, than in low-yielding cultivars, Haags Blaue and Sonet. Inoculation treatments also showed significantly higher shoot (3.15-3.39% N) and root (1.96-2.54% N) nitrogen content. Biological nitrogen fixation rate, measured by the nitrogen difference method, ranged between 87.9 and 90.8% depending on both bacterial strain and host cultivar. The field experiment showed significant increases in shoot (14.4-47.9%), root (11.9-29.1%) and seed (13.8-68.6%) dry weight, plant height (3.6-10.7%), pod plant-1 (10.7-50.6%) and chlorophyll content (5.7-20.7%) following inoculation of the three narrow-leafed lupin cultivars. Uninoculated plants grown in soil in the greenhouse experiment and in the field experiment both produced some nodules, which showed the evidence of presence of indigenous nodule-forming and nitrogen-fixing bacteria. Among the 3 liquid cultures, HAMBI 3115 performed best in terms of lupin growth, yield and biological nitrogen fixation in both greenhouse and field experiments. The performance of the peat-based commercial inoculant of HAMBI 3118 strain exceeded all other inoculants in the field experiment but not in the greenhouse experiment, showing the importance of the carrier. The results indicated that lupin growth and yield are strongly affected by Bradyrhizobium inoculation and soil characteristics. Selection of a suitable Bradyrhizobium strain for inoculation and growing cultivars according to their soil preferences can maximize lupin yield. The suitability of HAMI 3115 for making peatbased inoculants should be tested.
Subject: Lupinus angustifolius
Lupinus albus
nitrogen content
biological nitrogen fixation

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