Investigating Effective Factors in Improving Plant Growth by Native Phosphate-dissolving Bacteria Isolated from Wheat

Wheat is one of the most important strategic products in providing food security for the growing world population. The purpose of this research is to isolate and identify plant growth-promoting bacteria from the wheat rhizosphere and their inhibitory effect on the growth of the pathogenic fungus Fusarium sp. isolated from wheat. The initial screening of 100 bacterial strains isolated from wheat roots was done based on their ability to dissolve phosphate. The effective factors in plant growth and inhibition of fungal pathogens, such as the ability to produce IAA, siderophores, protease, biofilm, bacterial swarming motility, tolerance to salt, seed germination, and seed vigor tests, were investigated. In the initial screening, four bacterial isolates with the highest amount of phosphate dissolution were identified based on morphological and biochemical characteristics as well as the sequence of 16S rRNA region belonging to Curtobacterium sp., Arthrobacter sp., Acinetobacter calcoaceticus, and Cellulosimicrobium sp.; Curtobacterium sp. had the highest amount of IAA (6.14μg/ml), siderophore (2.25cm), protease (1.4cm), and the highest tolerance to salinity (20%) and phosphate dissolution (375.3mg/ml). In the swarming motility test, the highest values were related to Arthrobacter sp. and Curtobacterium sp. at 2.7 and 2.2cm, respectively. The highest amount of biofilm formation was associated with Acinetobacter calcoaceticus and Curtobacterium sp. with an average absorption coefficient of 0.153 and 0.139, respectively. The highest and lowest average values of percentage inhibition of pathogenic fungus colony growth were evaluated in Curtobacterium sp. isolate with a value of 57.3%, and Cellulosimicrobium sp. isolate with 33%, respectively

Unleashing the Potential of Bacterial Isolates from Apple Tree Rhizosphere for Biocontrol of Monilinia laxa: A Promising Approach for Combatting Brown Rot Disease.

peer reviewedMonilinia laxa, a notorious fungal pathogen responsible for the devastating brown rot disease afflicting apples, wreaks havoc in both orchards and storage facilities, precipitating substantial economic losses. Currently, chemical methods represent the primary means of controlling this pathogen in warehouses. However, this study sought to explore an alternative approach by harnessing the biocontrol potential of bacterial isolates against brown rot in apple trees. A total of 72 bacterial isolates were successfully obtained from the apple tree rhizosphere and subjected to initial screening via co-cultivation with the pathogen. Notably, eight bacterial isolates demonstrated remarkable efficacy, reducing the mycelial growth of the pathogen from 68.75 to 9.25%. These isolates were subsequently characterized based on phenotypic traits, biochemical properties, and 16S rRNA gene amplification. Furthermore, we investigated these isolates' production capacity with respect to two enzymes, namely, protease and chitinase, and evaluated their efficacy in disease control. Through phenotypic, biochemical, and 16S rRNA gene-sequencing analyses, the bacterial isolates were identified as Serratia marcescens, Bacillus cereus, Bacillus sp., Staphylococcus succinus, and Pseudomonas baetica. In dual culture assays incorporating M. laxa, S. marcescens and S. succinus exhibited the most potent degree of mycelial growth inhibition, achieving 68.75 and 9.25% reductions, respectively. All the bacterial isolates displayed significant chitinase and protease activities. Quantitative assessment of chitinase activity revealed the highest levels in strains AP5 and AP13, with values of 1.47 and 1.36 U/mL, respectively. Similarly, AP13 and AP6 exhibited the highest protease activity, with maximal enzyme production levels reaching 1.3 and 1.2 U/mL, respectively. In apple disease control assays, S. marcescens and S. succinus strains exhibited disease severity values of 12.34% and 61.66% (DS), respectively, highlighting their contrasting efficacy in mitigating disease infecting apple fruits. These findings underscore the immense potential of the selected bacterial strains with regard to serving as biocontrol agents for combatting brown rot disease in apple trees, thus paving the way for sustainable and eco-friendly alternatives to chemical interventions

Effect of fungal and bacterial biological agent against bean common blight caused by Xanthomonas axonpodis pv. Phaseoli

Introduction:The bean common blight caused by Xanthomonas axonpodis pv. phaseoli is one of the most important pathogens of bean, which is a serious problem to produce this crop in western regions of the country. Due to the severe damage of this pathogen, using fungal and bacterial bio-control agents can be as an efficient way to reduce the damage of disease on bean. The aim of this study was to evaluate the controller effects of fungal and bacterial biological agents including Trichoderma harzianum, T. virens, Bacillus subtillis and Pseudomonas fluorescence in laboratory and greenhouse conditions on bacteria of bean common blight. Materials and methods: In order to study the effects of biological agent against Xap, in the first stage, was to investigate the percentage growth inhibition of Xapby biological agents under laboratory conditions. In the next step, the interaction of biological agent and pathogenesis bacteria on bean plant was evaluated in a completely randomized design, four replications and biological agent’s treatments are under the greenhouse conditions. Indices such as root and shoot fresh weight, root and shoot dry weight, height roots and stems of beans and disease severity were measured to analyse the control power of the biological agents. Results: In laboratory conditions, fungal biological agents of T. harzianum with an average diameter of inhibitor halo of 42 mm and inhibiting 56.67% of the growth had highest controller effect on pathogenesis bacteria. However, in greenhouse conditions, P. fluorescence bacteria had better performance and all plant indices under this treatment showed a significant growth. The combined treatment of P. fleurescence + T. virens was the best treatment in this experiment with reducing 79.4% of disease symptoms. Treatments P. fleurescence+T. harzianum and B. subtillis+P. fleurescence with amount of 69.6 and 55.9% reduced the symptoms, respectively, and are in following levels. Discussion and conclusion: Therefore, the use of biological agents can largely reduce the bean common blight, so that it can be an efficient and environmentally friendly method used