Isolation and characterization of soybean‐associated bacteria and their potential for plant growth promotion

Abstract

Endophytic and epiphytic bacteria were isolated from two soybean cultivars (Foscarin and Cristalina). Significant differences were observed in bacterial population densities in relation to season of isolation, soybean growth phase and the tissues from which the isolates were obtained. The isolates were identified by partial 16S rDNA sequence analysis, with most of the isolates belonging to the Pseudomonaceae, Burkholderiacea and Enterobacteriaceae groups. The potential of the isolates for plant growth promotion was evaluated by screening for indoleacetic acid (IAA) production and mineral phosphate solubilization; 34% of endophytic bacteria produced IAA and 49% were able to solubilize mineral phosphate whereas only 21% of epiphytic bacteria produced IAA although 52% were able to solubilize mineral phosphate. A high frequency of IAA producing isolates occurred in the early ripening Foscarin cultivar whereas a high percentage of phosphate solubilizing isolates were obtained from plants in the initial development stage (V6). We also found that 60% of endophytic and 69% of epiphytic isolates that produced IAA and solubilized mineral phosphate were also able to fix nitrogen in vitro. The soybean-associated bacteria showing characteristics related to plant growth promotion were identified as belonging to the genera Pseudomonas, Ralstonia, Enterobacter, Pantoea and Acinetobacter.

Seleção de bactérias promotoras de crescimento no abacaxizeiro cultivar Vitória durante a aclimatização

“…Em relação ao uso de inoculantes, ainda são escassos os trabalhos com abacaxizeiros, porém é consenso que bactérias epifíticas, que habitam a superfície vegetal (Baldotto & Olivares, 2008), e as bactérias endofíticas, que habitam o interior dos tecidos vegetais (Halmann et al, 1997), podem promover o crescimento da planta hospedeira, conforme já descrito para diversas culturas, como arroz (Verma et al, 2001), soja (Cattelan et al, 1999;Kuklinsky-Sobral et al, 2004) e milho (Chabot et al, 1998). Os mecanismos de promoção de crescimento pelas bactérias epifíticas e endofíticas incluem diferentes ações, como a fixação biológica de nitrogênio (KuKlinsky-Sobral et al, 2004), solubilização de fosfatos (Chabot et al, 1998;Verma et al, 2001), biossíntese de fito-hormônios (Lucangeli & Bottini, 1997), influência na atividade enzimática da 1-aminociclopropano 1-carboxilato (ACC) deaminase (Rothballer at al., 2008), controle biológico (Byrne et al, 2005), síntese de sideróforos (Lacava et al, 2008) e indução de resistência sistêmica a patógenos na planta hospedeira (Kloepper et al, 1999 Efeitos positivos da inoculação de bactérias promotoras de crescimento foram verificados na abacaxicultura, principalmente quando as bactérias inoculadas também são fixadoras de nitrogênio atmosférico (Weber et al, 2003).…”

“…Os mecanismos de promoção de crescimento pelas bactérias epifíticas e endofíticas incluem diferentes ações, como a fixação biológica de nitrogênio (KuKlinsky-Sobral et al, 2004), solubilização de fosfatos (Chabot et al, 1998;Verma et al, 2001), biossíntese de fito-hormônios (Lucangeli & Bottini, 1997), influência na atividade enzimática da 1-aminociclopropano 1-carboxilato (ACC) deaminase (Rothballer at al., 2008), controle biológico (Byrne et al, 2005), síntese de sideróforos (Lacava et al, 2008) e indução de resistência sistêmica a patógenos na planta hospedeira (Kloepper et al, 1999 Efeitos positivos da inoculação de bactérias promotoras de crescimento foram verificados na abacaxicultura, principalmente quando as bactérias inoculadas também são fixadoras de nitrogênio atmosférico (Weber et al, 2003). Já foram isoladas de abacaxizeiros bactérias diazotróficas pertencentes aos gêneros Burkholderia (Weber et al, 1999), Acetobacter (Tapia-Hernández et al, 2000) e Asaia (Weber et al, 2003).…”

A large diversity of non-rhizobial endophytes found in legume root nodules in Flanders (Belgium)

“…Certain NRE bacteria have beneficial effects on the host plants, including plant growth promotion (Vessey, 2003;Kuklinsky-Sobral et al, 2004;Ibañez et al, 2009;El-Tarabily et al, 2010;Tariq et al, 2014), nitrogen fixation (Andrews et al, 2010), siderophore mediated interactions (Rajendran et al, 2008;Andrews et al, 2010), increased promotion of plant stress tolerance (Andrews et al, 2010) and biological control of plant pathogens (El-Tarabily et al, 2010). Most legumes are good pioneer species, adapted to low nutrient soils and/or environments with heavy metals (Gonzalez-Andres et al, 2005;Vidal et al, 2009;Azcon et al, 2010).…”

Rhizosphere and endophytic bacteria for induction of salt tolerance in gladiolus grown in sodic soils

“…The identification was carried out using 16S rDNA sequencing and comparing them by BLAST database. Similar process was adopted in characterization by many earlier workers (Sturz et al 2000;Kuklinsky-Sobral et al 2004;Tank & Saraf 2010). …”