In vitro production of IAA by endophytic fungus Aspergillus awamori and its growth promoting activities in Zea mays

Abstract

Indole-3-acetic acid (IAA) plays an important role in plant microbe interactions. Current study explored the role of indole-3-acetic acid (IAA) as a signalling molecule for chemical dialogue between endophytic fungus and host plant roots. The endophytic fungus was isolated from the leaves of drought stressed Withenia somnifera and was identified as Aspergillus awamori Wl1 through ITS region of 18 S rDNA sequence. The isolated Wl1 strain was capable of producing important secondary metabolites, including IAA, phenols and sugars. Culture filtrate of the strain contained 24.2, 275.4 and 127.4 μg/mL of IAA, phenols and sugars, respectively. The strain has efficiently colonized the maize roots and enhanced the growth of host plant. In order to determine the role of IAA in root colonization by endophyte, we inhibited the biosynthesis of IAA. Inhibition of IAA production by foliar application of yucasin effectively reduced the colonization of endophyte in maize roots by 52%, whereas root application of yucasin has decreased the colonization frequency by 66%. However, the application of IAA restored the ability of Aspergillus awamori to colonize maize roots and significantly improved various growth parameters. From these observations, it is concluded that IAA plays a vital role in initiating a crosstalk between the two partners.