Characterization of the culturable component from rhizosphere zone of wheat and rice fields of Malwa region in Punjab

The present study was undertaken to characterize the dominant culturable fungal and bacterial biodiversity isolated from wheat and rice fields that may further help to study the pathogenic potential of these fungi to cause the yield losses in wheat and rice agro-ecologies. Soil samples were collected from the soil of the rhizosphere zone of rice and wheat fields of the Malwa region (Talwandi Sabo, Faridkot, Sardulgarh) in Punjab from 2018 to 2019 in three Intervals to assess the biodiversity of microorganisms. The microflora was isolated using the soil dilution plating technique. The fungal population obtained from the soil of wheat-rice rhizosphere comprised of Acremonium sp., Aspergillus spp. viz A. niger, A. flavus, A. ochraceus, and A. fumigatus, Alternaria spp. viz. A. alternata, A. brassicae, Curvularia lunata, Cladophialphora bantiana, Helminthosporium sp., Fusarium spp. viz. F. oxysporum, F. chalmydosporum, Mucor sp., Penicillium spp. viz. P. chrysogenum, P. expansum, Rhizpous spp. More than 30 bacterial strains were also isolated from the three different locations. The bacterial colonies were predominantly gram-positive rod-shaped or filamentous and gram-negative cocci. Among the ten fungal genera the Aspergillus spp. viz. A. niger, A. flavus, and Penicillium spp. viz. P. chrysogenum and P. expansum were dominant on potato dextrose agar (PDA) plates. The frequency of occurrence of common species in wheat soil samples was maximum for genus Aspergillus (A. niger, A. flavus) and Penicillium (P. chrysogenum) viz., 24.35%, 16.16%, 19.23%, respectively, while Acremonium sp., Aspergillus ochraceus, and A. fumigatus showed the minimum frequency of occurrence viz., 3.84%, 2.56%, and 3.84%, respectively. However, in rice fields, A. niger, A. flavus, P. chrysogenum, and P. expansum showed the maximum frequency of occurrence (19.14%, 13.82%, 15.95%, and 14.89%, respectively). The results showed that the genus Penicillium. and Aspergillus were dominant in rhizosphere soils of Talwandi sabo and Faridkot while genus Fusarium was prevalent in the Sarudulgarh region. The dominance of these fungal pathogens may be due to the release of aflatoxins by Aspergillus spp. and fumonisins by Fusarium spp., which may have an inhibitory effect on the survival of other microbial diversity.