Yellow Leaf Disease (YLD) is one of the most destructive diseases affecting arecanut, causing severe yield reduction and a decline in palm vigour. The present study was undertaken to isolate, enumerate, and characterise culturable rhizosphere bacterial communities associated with healthy and YLD-affected arecanut palms. Rhizosphere soil samples were collected from healthy and diseased gardens, and bacterial colonies were isolated using serial dilution and the spread-plate technique on nutrient agar medium. The purified isolates were characterised based on colony morphology, Gram reaction, and cell morphology. A total of 33 bacterial isolates were obtained and characterised. Of these, 29 isolates (87.88%) were Gram-positive, whereas only four isolates (12.12%) were Gram-negative, indicating the predominance of Gram-positive bacteria in the arecanut rhizosphere. Colony morphology exhibited considerable diversity in colour and shape, with predominantly circular (73%) and serrated (27%) colonies. Microscopic examination revealed both cocci and rod-shaped bacterial cells. The predominance of Gram-positive bacteria and the higher culturable bacterial population in healthy rhizosphere soils suggest the presence of microbial communities that may contribute to nutrient cycling, plant growth promotion, and the suppression of soil-borne pathogens. These findings provide baseline information on culturable bacterial diversity associated with healthy and YLD-affected arecanut rhizospheres.
K. Premalatha, G. Naik, K. Satish et al.· Plant cell biotechnology and...· 0 citations
Yellow leaf disease (YLD) is a destructive disease of arecanut (Areca catechu L.) that is associated with progressive yellowing, root deterioration, reduced nut production, and palm decline. This study compared culturable rhizosphere fungal populations in healthy and YLD-affected arecanut gardens and characterised the isolates using morphological and molecular methods. Twenty-five rhizosphere soil samples were processed using serial dilution plating on rose bengal agar. Fungal colonies were purified on potato dextrose agar, and genomic DNA was extracted. The internal transcribed spacer region was amplified using ITS-1 and ITS-4 primers, sequenced, and analysed through BLAST searches against the NCBI nucleotide database. Healthy rhizosphere soils contained higher populations of beneficial microorganisms than disease-affected soils. Trichoderma species were predominant, particularly T. asperellum and T. harzianum, while Fusarium, Talaromyces, Gibberella, and Diaporthe taxa were also identified. The abundance of Trichoderma isolates in healthy soils was consistent with their recognised associations with root development, nutrient mobilisation, water uptake, and suppression of soil-borne pathogens. The study demonstrates an association between palm health and the composition of culturable rhizosphere fungi and provides a basis for further functional and culture-independent investigations of the arecanut rhizosphere.
K. Premalatha, B. G. Naik, K. Hariprasad et al.· Journal of Advances in Biolo...· 0 citations
