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The association between microbes and plant roots involves a complex chemical dialogue featured by IAA and flavonoids in addition to other signals. Current study is focused on the role of IAA and flavonoids as essential elements of the chemical dialogue between an endophytic fungus and maize roots. The strain was isolated from the leaves of Withania somnifera and was identified as Aspergillus fumigatus greenish by 18S rDNA sequence. Culture filtrate of the strain contained phyotstimulant (IAA, ammonia and ACC) and signaling compounds including IAA, flavonoids and flavonols. The strain effectively colonized the maize roots and enhanced its growth. In order, to determine the effect of IAA and flavonoids on the ability of the endophyte to colonize maize roots, we inhibited the release of IAA and flavonoids in maize separately which reduced the colonization of endophyte in maize root to 66% and 55% of the untreated control. Similarly, application of IAA in combination with endophyte enhanced root colonization by 90% in zone of cell division, 66% in the zone of elongation and 30% in the zone of maturation. These findings determined that IAA and flavonoids are among the key players of the complex chemical dialogue between plant root and fungal endophyte. [ABSTRACT FROM AUTHOR]

Abstract: Endophytic fungi are little known for exogenous gibberellins (GAs) production and plant growth promotion under salt stress conditions. We isolated 13 endophytic fungi from soybean roots, which were screened on Waito-C rice for plant growth promoting capacity. Endophytic strain, GMH-1a exhibited maximum growth during screening and thus was investigated for GAs production and host plant interaction. GMH-1a was identified as a new strain of Aspergillus fumigatus sp. LH02 through phylogenetic analysis of 18S rDNA sequence. Analysis of GMH-1a culture filtrate showed presence of GA4 (24.8ng/ml), GA9 (1.2ng/ml) and GA12 (9.8ng/ml). Soybean plants inoculated with GMH-1a significantly increased shoot length, shoot fresh and dry biomass, leaf area, chlorophyll contents and photosynthetic rate under salt stress (70 and 140mM) as compared to non-inoculated plants. GMH-1a inoculated plants had contained significantly lower endogenous abscisic acid (ABA) and elevated free proline, salicylic acid (SA) and jasmonic acid (JA) contents in comparison to their respective control treatments. Isoflavones, quantified through excessive HPLC analysis, showed that GMH-1a inoculated plants with/without salt stress contained higher isoflavones than non-inoculated plants and with/without NaCl stress. This novel endophytic fungus has reprogrammed soybean metabolism to improve plant growth and increase isoflavone contents under salt stress. [Copyright &y& Elsevier]