Role of Arbuscular Mycorrhizae (AM) Fungi and Multi Bioinoculants in Cotton Plant Growth

Aim: The present study reflects the effect of Arbuscular Mycorrhizae (AM) fungi and other bioinoculants on the growth of cotton seedlings.
Study Design: Screening of efficient biofertilizers from undisturbed forest soils to improve the crop yield of cotton in barren lands of Mahabubnagar District.
Place and Duration of Study: Department of Microbiology, Palamuru University, Mahabubnagar, Andhra Pradesh, India, between May 2011 and February 2012.
Methodology: Mahyco hybrid variety, the most widely cultivated variety in Mahabubnagar District, Andhra Pradesh, India was selected among the sixteen varieties of cotton seeds for this study. Soil samples were analyzed for physicochemical characteristics. Seven different isolates of AM fungi were maintained as pure cultures in laboratory, which were isolated from different Agro-forestry tree rhizosphere soils. Among these pure cultures, R1-R2 has shown maximum colonization with Mahyco variety and this isolate was identified as Glomus mosseae. Mahyco hybrid variety was also tested with three different bioinoculants (Rhizobium sp., Azospirillum sp., Bacillus sp.) along with the combination of AM pure culture of R1-R2. These three potential bioinoculants were identified based on 16S rRNA gene sequence. Preliminarily Mahyco hybrid variety was investigated with individual pure cultures of AM fungi and with other bioinoculants. R1-R2 were taken in single, dual, triple and multicombinations with other three bioinoculants.
Results: In single combination M+R1-R2 showed the best growth by M+Rhizobium, followed by M+Bacillus and in dual combination M+R1-R2+Rhizobium and in triple combination M+R1-R2+Rhizobium+Azospirillum and in multicombination i.e. M+R1-R2+Rhizobium+Azospirillum+Bacillus showed the best growth among all the combinations.
Conclusion: The multicombination mediates increased the cotton growth characteristics. The effect of multicombination was not significantly different in treatment affected by various varieties. Inoculation of multicombination along with AM pure culture resulted significant increase in shoot and root length of cotton plant. So multicombination was proved to be superior.