Geographic patterns of symbiont abundance and adaptation in native Australian Acacia–rhizobia interactions

Abstract

Summary1. The importance of plant-soil interactions in land reclamation, and the management and restoration of functioning native ecosystems, is becoming widely recognized. However, relatively little is known about broad-scale patterns of genetic variation and adaptation in wild plant-soil symbiotic interactions. 2. The current study is part of a larger project examining patterns of genetic variation and adaptation in host and symbiont populations across their geographical ranges using two widespread native Australian Acacia spp. ( A. salicina , A. stenophylla ) and associated populations of rhizobial bacteria. 3. A total of 58 sites were characterized with regard to symbiont population sizes, soil chemistry and environmental parameters. Rhizobial abundance was negatively correlated with a small number of soil factors, including nitrogen, and positively correlated with organic carbon and cation exchange capacity. 4. There were clear differences between host species in seedling growth responses in glasshouse trials using pots inoculated with native soils. While A. salicina grew equally well with soils from A. stenophylla and A. salicina sites, A. stenophylla grew best when inoculated with its own soils, indicating broad-scale adaptation to its own rhizobia. 5. Rhizobial abundance in these soils was also strongly correlated to variation in nodulation and host growth, indicating that abundance may be a good indicator of the relative effectiveness of rhizobial populations. 6. The clear differences in specificity and effectiveness of host-symbiont associations, even among related species, suggests that better knowledge of these systems at multiple spatial scales is central to understanding the factors that influence the ecology and evolution of plant and soil communities, and has potential to increase the cost-effectiveness of restoration programs.

Abundance of Legume Nodulating Bacteria in Soils of Diverse Land Use Systems in Cameroon

“…Most of the soils examined contained moderate or high populations of LNB. This result is similar to the results of Martyniuk and Oroń [24] in Polish soils.…”

Development of environmental friendly bioinoculate for peanut (Arachis hypogea L.) production in Eastern Ethiopia

“…The soil of the study sites had the native rhizobia capable of nodulating peanut greater than 10 2 g −1 of soil. Large number of native rhizobia in the two soils could be because of the presence of conducive soil properties (Yousef et al 1987;Thrall et al 2007;Drew et al 2012) and cultivating the host plant for long time (Chemining'wa and Vessey 2006;Kimiti and Odee 2010). However, the previous experiment conducted this region showed that inoculation of locally isolated rhizobia improved the yield of common bean (Anteneh 2016), Fababean (Argaw et al 2012a) and Field pea (Argaw et al 2012b), though the soil had > 10 3 rhizobia g −1 soil.…”

“…Hence the indigenous rhizobia may interfere the effectiveness of inoculated effective isolate thereby causes lack of success of inoculation in improving nodulation and N 2 fixation of peanut (Hitbold et al 1983;Kvien and Pallas 1986). However, if the native rhizobia is symbiotically effective, increase in native rhizobia population increased the yield of pulses (Thrall et al 2007).…”

Invasive Lespedeza cuneata and native Lespedeza virginica experience asymmetrical benefits from rhizobial symbionts

“…It would be very interesting to know if the disproportionate benefits of L. cuneata reported here extend to these other kinds of symbioses. Different strains of microbial symbionts can have differential fitness effects on different plant hosts (Cardinale et al 2008;Helgason et al 2002;Rangin et al 2008;Rincon-Rosales et al 2009;RodriguezEcheverria et al 2012;van der Heijden et al 1998), and these differential effects may be related to the degree of "familiarity" between the host and the symbiont (Klironomos 2003;Rodriguez-Echeverria 2010;Rodriguez-Echeverria et al 2012). For example, in a Mediterranean dune system, the legume-rhizobium symbiosis leads to higher nodulation rates, nitrogenase activity, and plant growth when native legumes are paired with native rhizobacteria and when exotic legumes are paired with rhizobacteria from their home range (Rodriguez-Echeverria et al 2012;Thrall et al 2007).…”

“…Consequently, some invasive legumes do not appear to be limited by the density or community composition of soil rhizobia (Birnbaum et al 2012). However, the legume-rhizobium symbiosis is more effective when invasive Acacia are matched with bacteria from their home range in comparison with native bacteria (Rodriguez-Echeverria et al 2012;Thrall et al 2007). The legume Leucaena leucocephala failed to survive in its invaded range until its corresponding symbiotic rhizobia were introduced (Richardson et al 2000).…”