title: Influence of soil reaction on diversity and antifungal activity of fluorescent pseudomonads in crop rhizospheres.
abstract: The diversity and antifungal activity of fluorescent pseudomonads isolated from rhizospheres of tea, gladiolus, carnation and black gram grown in acidic soils with similar texture and climatic conditions were studied. Biochemical characterisation including antibiotic resistance assay, RAPD and PCR-RFLP studies revealed a largely homogenous population. At soil pH (5.2), the isolates exhibited growth with varying levels of siderophore production, irrespective of crop rhizospheres. Two isolates with maximum chitinase production showed antagonism. The bacterial populations in general lacked the ability to produce deleterious traits such as cellulase, pectinase and hydrogen cyanide. However, increased pH levels beyond 5.2 caused reduction in metabolite production with reduced antifungal activity. The homogeneity of the bacterial population irrespective of crop rhizospheres together with decreased secondary metabolite production at higher pH levels reinstated the importance of soil over host plant in influencing rhizosphere populations. The studies also yielded acid tolerant chitinase producing antagonistic fluorescent pseudomonads.
authors.affiliation: Floriculture Division, Institute of Himalayan Bioresource Technology, Palampur 176 061, Himachal Pradesh, India.
authors.forename: Rajni
authors.initials: R
authors.lastname: Verma
authors.forename: Ajit Singh
authors.initials: AS
authors.lastname: Naosekpam
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kumar
authors.forename: Ramdeen
authors.initials: R
authors.lastname: Prasad
authors.forename: V
authors.initials: V
authors.lastname: Shanmugam
mesh_terms: D044822:Biodiversity; D002480:Cellulase / Q000032:analysis; D016000:Cluster Analysis; D017931:DNA Primers; D024881:Drug Resistance, Bacterial / Q000502:physiology; D004586:Electrophoresis; D005453:Fluorescence; D005670:Fusarium; D006856:Hydrogen Cyanide / Q000032:analysis; D007194:India; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology*; D011096:Polygalacturonase / Q000032:analysis; D012150:Polymorphism, Restriction Fragment Length; D011549:Pseudomonas / Q000737:chemistry* / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics; D019105:Random Amplified Polymorphic DNA Technique; D017262:Siderophores / Q000032:analysis; D012988:Soil Microbiology
chemical_list: D017931:DNA Primers; D012335:RNA, Ribosomal; D017262:Siderophores; D006856:Hydrogen Cyanide; D011096:Polygalacturonase; D002480:Cellulase