Abstract
Rhizobia play an important role in plant nutrition by fixing nitrogen that is subsequently available for uptake by plants. In Myanmar, it has been difficult to characterize the nitrogen-fixing indigenous bradyrhizobia strains. In this study, 120 strains were isolated from five major soybean-growing regions of Myanmar. The strains were characterized based on sequence analysis of the 16S-23S rRNA internal transcribed spacer (ITS) region. Determination of nodulation types of native isolates was based upon their compatibility between strain and soybean cultivars by inoculation test. Our goal was to describe the polygenetic diversity among indigenous bradyrhizobial strains isolated from Myanmar and to identify their nodulation types. Sequence analysis indicated that all isolates belonged to the Bradyrhizobium genus and were conspecific with B. liaoningense,B. elkanii,Bradyrhizobium spp., B. japonicum and B. yuanmingense. A phylogenetic tree showed that 40, 33.3, 19.2, 5 and 2.5% of the isolates were related to B. liaoningense,B. elkanii,Bradyrhizobium spp., B. japonicum and B. yuanmingense, respectively. These results suggested that B. liaoningense and B. ellkanii were the predominant Bradyrhizobium species present in Myanmar soils.B. elkanii, B. liaoningense and Bradyrhizobium spp. strains were dominant in acid soils, slightly acid to slightly alkaline soils and alkaline soils, respectively. Among tested isolates, Type A strains accounted for 74% of the isolates, while Type B and C strains accounted for 22 and 4%, respectively.It can be concluded that the diversity and distribution of indigenous bradyrhizobia differed markedly among sampling sites and among sites within the same region, and were affected by soil pH and climate. Determination of nodulation types of indigenous brayrhizobia provides useful information for selection of strains compatible with different soybean cultivars. This is the first report describing B. liaoningense strains isolated from soybean in Myanmar. Key words: Indigenous bradyrhizobia, internal transcribed spacer (ITS), Myanmar, phylogenetic diversity, soybean, nodulation type.
Highlights
Soybean (Glycine max L.) plays an important role in plant nutrition by fixing nitrogen that is subsequently available for uptake by plants.In the world, soybean is the major grain legume crop, representing about 50% of global legume acreage and 68% of global legume production (Herridge et al, 2008)
Our results showed that B. elkanii and B. liaoningensewere found as the major dominant species, and Bradyrhizobium spp., B. japonicum and B. yuanmingense as the minor species in Myanmar soils
B. elkanii strains were dominant in acid soils with a pH 5.1 and 6.7
Summary
Soybean (Glycine max L.) plays an important role in plant nutrition by fixing nitrogen that is subsequently available for uptake by plants.In the world, soybean is the major grain legume crop, representing about 50% of global legume acreage and 68% of global legume production (Herridge et al, 2008). Soybean plays an important role in the economy of Myanmar, due to its high nitrogen fixing ability through symbiosis with rhizobia. Soybean-nodulating bacteria belong to the genus Bradyrhizobium and are gram-negative, slow-growing and alkali-producing when cultured on yeast extract mannitol agar (YMA) medium (Vincent, 1970). The diversity of soybean-nodulating bradyrhizobia depends on climate and soil properties (Adhikari et al, 2012). The community structure of bradyrhizobia varies according to the soybean cultivar, the host soybean Rjgenotype, and cultivation temperature (Minami et al, 2009; Shiro et al, 2012). Howieson and Ballard (2004) stated that the soybean-nodulating bradyrhizobial community might vary depending on the host cultivar and cultivation temperature even in the same field and on geographical, soil texture, soil pH, salinity, and other differences among fields. The abundant diversity of rhizobia in the soil provides a large source of natural germplasm to select strains with desired characteristics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
