Abstract:
Casuarinaequisetifolia (Kasa) is an actinorhizal plant which is used for rehabilitation of poor and disturbed
soil throughout the world. Actinorhizal plants which were colonized by Frankia sp. enhance the soil fertility
due to frankial colonization in root nodules. However, few studies were reported on non-frankial
colonization and its impact on plant growth and soil fertility. Thus this study was carried out to investigate
the unrevealed information on actinomycete consortia residing the nitrogen fixing root nodules of C.
equisetifolia. The actinomycete were successfully isolated from surface sterilized root nodules by using
double layered agar plate technique and also isolates were tested on reinfectivity on Casuarina seedlings.
Three different actinomycetes were able to identify as Frankia sp., Micromonospora sp., and novel symbiont
as Streptomyces sp. from nitrogen fixing root nodules of Casuarina plants. Further, co-existence of all three
isolates were observed in nitrogen free and nitrogen enriched Yeast Mannitol Agar medium (YMA). Frankia
sp. promoted the shoot and root growth by 87% and 55% respectively with nodulation of C. equisetifolia and
whereas Micromonospora sp. promoted the root and shoot growth by 28% without nodulation. In contrast
Streptomyces sp. was able to trigger the lateral root formation of C. equisetifolia which indicate the ability of
the microorganism to alter host development system. This study provides novel data on root inhabiting
Streptomyces sp. which could play a vital role in enhancing plant growth, exchanging complex signals
between plant and microorganisms. These results suggest that the root inhabiting microbial consortium of C.
equsetifolia would significantly contribute to the development of plant growth.
