Characterization of Endophytic Microorganisms of Rice(Oryza sativa L.)Potentials for Blast Disease Biocontrol and Plant Growth Promoting Agents

One hundred twenty-five endophytic microorganisms were isolated from the roots,stems,and leaves of four prominent rice cultivars growing in temperate regions.Their potential to combat rice blast disease and promote plant growth was investigated.The dual culture tests highlighted the strong antagonistic activity of five fungal(ranging from 89%–70%)and five bacterial(72%–61%)endophytes.Subsequent examination focused on volatile compounds produced by selected isolates to counter the blast pathogen.Among these,the highest chitinase(13.76μg mL−1)and siderophore(56.64%),was exhibited by Aspergillus flavus,and the highest HCN production was shown by Stenotrophomonas maltophilia(36.15μM mL−1).In terms of growth promotion traits,Aspergillus flavus and Enterobacter cloacae excelled in activities viz,phosphorous solubilization,ammonia production,auxin and gibberellic acid production,and nitrogen fixation.The Identity of these endophytes was confirmed through molecular analysis as Trichoderma afroharzianum,Trichoderma harzianum,Penicillium rubens,Aspergillus flavus,Stenotrophomonas rhizophila,Stenotrophomonas maltophilia,Bacillus cereus,Enterobacter cloacae,and Bacillus licheniformis.Under greenhouse conditions,the highest disease control was shown by isolate Bacillus licheniformis and A.flavus with an inhibition of 79%,followed by S.rhizophila(77%)and T.afroharzianum(73%).The overall results of this study showed that Bacillus licheniformis and Stenotrophomonas rhizophila have great potential to be used as bio-stimulant and biocontrol agents to manage rice blast disease.

Rhodotorula mucilaginosa BPT1 can form arthrospore in response to cold-temperature

Objective:To study carbon and nitrogen utilization pattern and arthrospore formation in a psychrotolerant yeast isolate Rhodotorula mucilaginosa(R.mucilaginosa)BPT1.Methods:Growth of the yeast on minimal synthetic medium supplemented with various carbon and nitrogen compounds as sole carbon or nitrogen source has been studied.Various physico-chemical parameters such as pH,restricted oxygen supply,temperatures,media composition and presence of methionine were tested to examine their effect on arthrospore formation by this known opportunistic pathogen.Results:The psychrotolerant isolate BPT1 identified on the basis of D1/D2 domain of large rDNA sequence characteristics as R.mucilaginosa showed some deviation in carbon and nitrogen utilization patterns from those of other strains of R.mucilaginosa in the CBS data base.Intriguingly,the isolate produced sub-surface hyphal rays around its colony at lower temperatures(4℃and 20℃)on PDA medium;the ray was found to be linearly arranged arthrospores.The arthrospore was not produced in liquid medium,or in presence of methionine or under micro-aerobic condition or at higher temperature.Conclusions:The investigation showed a novel feature i.e.arthrospore was formed by this yeast isolate under specific set of conditions.The results reiterated that only physiological and morphological characteristics were not sufficient to identify a yeast.The ability of R.mucilaginosa to form arthrospores seems to be an adaptive feature in response to extreme environmental condition,and represents adaptive ability having something to do with its ubiquity.