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Plant Growth-Promoting Rhizobacteria (Pgpr) Increase Yield, Growth And Nutrition Of Strawberry Under High-Calcareous Soil Conditions

Plant growth promoting effects of Alcaligenes 637Ca, Staphylococcus MFDCa-1, MFDCa-2, Agrobacterium A18, Pantoea FF1 and Bacillus M3 were tested on strawberry cv. ‘Aromas’ based on yield, number, and weight of fruit, leaf area, vitamin C, total soluble solids (TSS), acidity and ionic composition of leaves under calcareous soil conditions. The results demonstrated that all of bacterial treatments significantly affected all parameters tested. The best result was obtained from 637Ca treatment, which significantly increased fruit yield, number and weight about 47.5, 34.7, and 9.4%, respectively, compared to control. Except for magnesium (Mg) and zinc (Zn) in the leaf, the concentrations of all plant tissue nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), copper (Cu), manganese (Mn), boron (B)] were significantly increased by bacterial treatments tested. The data in the present study showed that all bacterial treatments including Alcaligenes 637Ca, Staphylococcus MFDCa-1, MFDCa-2, Agrobacterium A18, Pantoea FF1, and Bacillus M3 to strawberry plants can ameliorative the deleterious effect of high lime on fruit yield, growth and nutrition. These results suggested that plant growth-promoting Rhizobacteria (PGPR) treatments could be offer an economic and simple means to increased plant resistance for high calcareous soil conditions.

Effects of indole-3-butyric acid (IBA), bacteria and radicle tip-cutting on lateral root induction in Pistacia vera

Summary Experiments were conducted to determine the effects of 50 mg l–1 and 100 mg l–1 indole-3-butyric acid (IBA), each of three strains of non-pathogenic Agrobacterium rubi (A1, A16 and A18), a non-pathogenic strain of Bacillus subtilis (OSU-142), and radicle tip-cutting (RC) alone, or a combination of bacteria and RC on the number of lateral roots, plant height, stem diameter, root length, and fresh and dry root weights of Pistacia vera seedlings. Treatment of germinated seeds of P. vera with IBA, bacteria, RC, or bacteria plus RC, caused significant increases in lateral root formation in seedlings. Treatments with 50 mg l–1 and 100 mg l–1 IBA, RC, A. rubi A1, A16, A18, B. subtilis OSU 142, RC+A1, RC+A16, RC+A18 or RC+OSU-142 increased average lateral root numbers from 2.1 in untreated controls, to 8.4, 10.3, 5.3, 7.8, 6.9, 6.2, 5.4, 8.1, 7.8, 5.9 and 5.4, respectively. IBA (100 mg l–1) gave the highest number of lateral roots. Agrobacterium rubi strain A1 was found to be more effective than the other bacterial strains, RC or control treatments in increasing the numbers of lateral roots.

Plant Growth Promoting Rhizobacteria as Alleviators for Soil Degradation

Soil degradation refers to decline in the soil’s productivity through deterioration of its physical, chemical, and biological properties. The most important processes and causes of degradation are water–wind erosion, salinization, alkalinization, acidification, and leaching and soil pollution. The rate of soil degradation is directly related to unsuitable land use. While growers routinely use physical and chemical approaches to manage the soil environment to improve crop yields, the application of microbial products for this purpose is less common. However, plant growth promoting rhizobacteria (PGPRs) can prevent the deleterious effects of one or more stressors from the environment. These beneficial microorganisms can be a significant component of management practices to achieve the attainable yield in degraded soil. In such soils, the natural role of stress-tolerant PGPRs in maintaining soil fertility is more important than in conventional agriculture. Besides their role in metal detoxification/removal, salinization, and acidification, rhizobacteria also promote the growth of plants by other mechanisms such as production of growth promoting substances and siderophores. Remediation with PGPRs is called bioremediation in degraded soil and is another emerging low-cost in situ technology (Cohen et al. Int J Green Energy 3:301–312, 2004) employed to remove or alleviate pollutants, salinity, and acidification stress from the degraded land. The efficiency of bioremediation can be enhanced by the judicious and careful application of appropriate heavy metal, salinity, acidity tolerant, and plant growth promoting rhizobacteria including symbiotic nitrogen-fixing organisms. This review presents the results of studies on the recent developments in the utilization of PGPR for direct application in soils degraded with heavy metals, salinity, and acidity under a wide range of agroecological conditions with a view to restore degraded soils and consequently, promote crop productivity in degraded soils across the globe and their significance in bioremediation.

The Actions of PGPR on Micronutrient Availability in Soil and Plant Under Calcareous Soil Conditions: An Evaluation over Fe Nutrition

The autotrophic plants need minerals for life cycle. An adequate supply of mineral nutrients is necessary for optimum plant growth. However, when adequate amounts of essential nutrients are present in soil, plants may still show deficiencies due to the non-availability of these mineral nutrients. Availability of plant nutrients such as Fe, Mn, Cu, B, and Zn are generally low in calcareous soils. Fe deficiency-induced chlorosis is the main limiting factor restricting plants growing worldwide. Microorganisms play an important role in enhancing nutrient availability to plant roots. Some PGPR increase the Fe availability in soil by decreasing pH by releasing organic acids or synthesizing low-molecular-weight iron-chelating agents (siderophores). In addition, some PGPR may increase Fe translocation and availability in plants via enhancing organic acid contents and FC-R activity in the root and leaves.

Nonsymbiotic and Symbiotic Bacteria Efficiency for Legume Growth Under Different Stress Conditions

In order to achieve maximum crop yields, excessive amounts of expensive fertilizers are applied in intensive farming practices. However, the biological nitrogen fixation via symbiotic and nonsymbiotic bacteria can play a significant role in increasing soil fertility and crop productivity, thereby reducing the need for chemical fertilizers. It is well known that a considerable number of bacterial species, mostly those associated with the plant rhizosphere, are able to exert a beneficial effect on plant growth. The use of those bacteria, often called plant growth-promoting rhizobacteria (PGPR), as biofertilizers in agriculture has been the focus of research for several years. The beneficial impact of PGPR is due to direct plant growth promotion by the production of growth regulators, enhanced access to soil nutrients, disease control, and associative nitrogen fixation. Legumes play a crucial role in agricultural production due to their capability to fix nitrogen in association with rhizobia. Inoculation with nodule bacteria called rhizobia has been found to increase plant growth and seed yields in many legume species such as chickpea, common bean, lentil, pea, soybean, and groundnut. However, both rhizobia and legumes suffer heavily and adversely from various abiotic factors. The impact of different stress factors on both PGPR and legume production is critically reviewed and discussed.

Effects of grafting height of MM106 rootstock on growth, lateral shoot formation and yield in apple trees

Summary Between 2004 and 2008, the effects of different grafting heights on sylleptic shoots were tested in the apple (Malus domestica Borkh.) cultivars ‘Granny Smith’ and ‘Gloster’, and cumulative fruit yields were evaluated. MM106 apple rootstocks were grafted 10, 20, 40, or 60 cm above soil level in August 2004. The results showed that an increased grafting height significantly decreased tree height in both cultivars. The tallest and shortest trees were observed at grafting heights of 10 cm (153.0 and 170.0 cm) and 60 cm (141.3 and 143.5 cm) in ‘Granny Smith’ and ‘Gloster’, respectively.Among the various grafting heights tested, 60 cm in ‘Granny Smith’ and 20 cm in ‘Gloster’ gave the largest stem diameters (17.6 mm and 16.8 mm, respectively). The number of lateral shoots increased significantly with increased grafting height in both cultivars. The largest numbers of lateral shoots in ‘Granny Smith’ (10.75) and ‘Gloster’ (2.00) were obtained from a grafting height of 60 cm, while 2.55 and zero lateral shoots occurred at 10 cm grafting height in ‘Granny Smith’ and ‘Gloster’, respectively. Shoot lengths decreased significantly by increasing the grafting height. Grafting heights of 10 cm and 60 cm resulted in the tallest and shortest shoots in both cultivars. Cumulative fruit yields were significantly affected by grafting height in both cultivars. The highest yield was found for a 60 cm grafting height in both ‘Granny Smith’ (11.295 kg tree–1) and ‘Gloster’ (4.818 kg tree–1).The results of this study suggest that grafting heights of 40 cm and 60 cm have the potential to promote branching and early bearing for apple fruit production in sustainable and organic agricultural systems.