Isolation and characterisation of endophytic actinobacteria and their effect on the growth and nodulation of chickpea (Cicer arietinum)

Background and aims: Some endophytic actinobacteria have been shown to be beneficial partners of the host plant by promoting plant growth as well as reducing plant disease symptoms. In this study, endophytic actinobacteria were isolated from the roots and nodules of chickpea plants and screened for their effects on the growth and nodulation of chickpea (Cicer arietinum). Methods: Four hundred and ninety-five actinobacteria were isolated from the roots and nodules of chickpea. Isolates were characterised on the basis of morphology, ability to sporulate and to enhance the growth of the rhizobial partner. Twenty-five cultures were co-inoculated with Mesorhizobium ciceri strain CC1192 onto chickpea seed to determine the effects on chickpea nodulation and growth in a low N sand-vermiculite system. Results: Seed treatment with Actinomadura sp. CP84B, Microbispora sp. CP56, Streptomyces spp. CP21A2 and CP200B increased the total dry weight of chickpea plants by 13% to 23% and the dry weight of nodules per plant by 14% to 23% at 8 weeks after planting, compared to plants treated with M. ciceri CC1192 alone. Conclusions: Endophytic actinobacteria isolated from chickpea roots have shown potential for use as microbial co-inoculants for improving the growth and rhizobial symbiosis of chickpea and can be termed “rhizobia-helper-bacteria”.