History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

Abstract

This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of which was coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus) and GENOPAR (Herbaspirillum seropedicae) reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.

Endophytic colonization of rice (Oryza sativa L.) by the diazotrophic bacterium Burkholderia kururiensis and its ability to enhance plant growth

“…This bacterium is a TCE-degrading bacterium isolated from an aquifer sample collected at a TCE-polluted site in Japan (Zhang et al 2000) and has the ability to fix nitrogen (Estrada-de los Santos et al 2001). The main driving force to determine this putative plant-bacteria association was the phylogenetic closeness between B. kururiensis and "B. brasilensis" (Baldani and Baldani 2005, Estradade los Santos et al 2001, Marin et al 2003, an endophytic diazotrophic bacterium isolated from rice in Brazil (Baldani et al 1997) which have a 100% similarity with the nifH gene sequence with B. kururiensis (Marin et al 2003). In fact, "B. brasilensis" has very recently been reclassified as B. kururiensis (CaballeroMellado et al 2007).…”

“…Several authors showed that endophytic diazotrophic bacteria as G. diazotrophicus (Sevilla et al 2001), H. seropediceae (Baldani et al 2000, Baldani andBaldani 2005, James and Olivares 1998), Azospirillum brasilense (Bacillo-Jiménez et al 2001), B. vietnamiensis (Trân Van et al 2000 and "B. brasilensis" (Baldani et al 2000, Baldani and Baldani 2005, Oliveira et al 2002 have the ability to increase the total dry matter of host plants to which they associate, suggesting an effect of these bacteria as plant-growth-promoting agents. We propose that B. kururiensis can be included in the associative category mentioned above, because it positively acts as a plant growth-promoting agent, also resulting in increased seed yields.…”

Associative diazotrophic bacteria in grass roots and soils from heavy metal contaminated sites

“…However, these findings are not in accordance with the fact that Herbaspirillum spp. are obligate endophytic organisms and therefore rarely occurring in soil (Baldani and Baldani 2005). However, Nóbrega et al (2004) pointed out that JNFb medium also detects species other than Herbaspirillum spp.…”

“…Among associative Nitrogen fixers, Azospirillum spp., Burkholderia and Herbaspirillum spp., are reported to occur in the ecto and endorhizosphere of grasses and in other monocotyledon species (Döbereiner 1978, Magalhães and Döbereiner 1984, Santos et al 2001, Baldani and Baldani 2005. In spite of the great volume of information about these bacteria, their occurrence in HM contaminated soils and HM effects on associative Nitrogen fixers are scarce.…”

Mecanismos de controle da murcha-de-esclerócio e promoção de crescimento em tomateiro mediados por rizobactérias

“…Dentre os mecanismos responsáveis pela promoção de crescimento vegetal por bactérias, frequentemente estão envolvidos a fixação biológica de nitrogênio (Baldani & Baldani, 2005), produção de ácido indol acético (Spaepen et al, 2009) e solubilização de fosfatos (Souchie et al, 2005). Por outro lado, os mecanismos de antagonismo direto relacionados ao controle biológico de fitopatógenos, normalmente envolvem a produção de enzimas líticas como quitinases (Kavino et al, 2010) e a produção de antibióticos difusíveis (Ahmad et al, 2008), enquanto o sequestro de ferro por sideróforos está associado tanto à promoção do crescimento quanto ao controle biológico (Glick, 1999;Ahmad et al, 2008).…”