Biological control of plant diseases is strongly emerging as an effective alternative to the use of chemical pesticides and fungicides. Stress tolerance is an important attribute in the selection of bacteria for the development of microbial inoculants. Fourteen salt-tolerant bacteria showing different morphological features isolated from the rhizosphere of maize were evaluated for different plant growth-promoting activities. All isolates showed auxin production ranging from 5 to 24 μg ⋅ ml–1 after 48 h incubation in tryptophan supplemented media. Phosphate solubilization ranged from 15 to 419 μg ⋅ ml–1. 1-aminocycloproprane- 1-carboxylate (ACC) deaminase activity was shown by 6 isolates, ammonia production by 9 isolates, siderophore production by 8 isolates while HCN production by 4 isolates. Four bacterial isolates with all plant growth-promoting properties also showed strong antagonistic activities against Fusarium oxysporum, F. verticillioides, Curvularia lunata and Alternaria alternata and abiotic stress tolerance against salinity, temperature, pH and calcium salts. Two selected bacterial isolates significantly enhanced the growth of pea and maize test plants under greenhouse conditions. The bacterial isolate M1B2, which showed the highest growth promotion of test plants, was identified as Bacillus sp. based on phenotypic and 16S rDNA gene sequencing. The results indicated that Bacillus sp. M1B2 is a potential candidate for the development of microbial inoculants in stressful environments.

We analyzed DNA damage, mitotic activity and polyploidization in Crepis capillaris callus cells during short- and long-term in vitro culture, and the influence of plant growth regulators on these processes. Changes in the concentration of growth regulators altered the stability of callus. The level of DNA damage was highly dependent on the growth regulator composition of the medium. Cytokinin at high concentrations damaged DNA in the absence of auxin. Short- and long-term callus differed in sensitivity to growth regulators. Mitotic activity changed when callus was transferred to medium with modified growth regulators. Callus cell nuclear DNA content increased with age and in response to plant growth regulators. Hormones played a role in the genetic changes in C. capillaris callus culture. We demonstrated the usefulness of C. capillaris callus culture as a model for analyzing the effect of culture conditions, including plant growth regulators, on genetic stability.

Trinexapac-ethyl is one of the newest growth regulators used in agriculture and horticulture. As a most growth retardants it acts by inhibiting gibberellin (GA) biosynthesis. A field study was conducted to determine the effects of trinexapac-ethyl on growth of winter wheat. Trinexapac ethyl was used alone (75 g a.i./ha and 125 g a.i./ha) and in the mixture with chlorocholine chloride (50 g a.i./ha + 675 g a.i./ha) at the 2nd node stage. Trinexapac-ethyl and its mixture with CCC activity was weather dependent. Their influence on the crop was strictly related to the temperature and rainfall during an individual year of trials. Plant growth regulators much more influenced winter wheat plants in abundant rainfall and higher temperature conditions. Lodging was not observed during the experiment.

The influence of adjuvants on the efficacy of the plant growth regulators: chlormequat chloride (CCC) and prohexadione-calcium was investigated in winter wheat in 2002 and 2003. Field trials were carried out in the Agricultural Experimental Farm in Winna Góra. The plant growth regulators were applied alone at normal rate and at a r educed rate with and without adjuvants. Two adjuvants were used: Adpros 85 SL, a methylated rapeseed oil and Break-Thru S-240, an organosilicone surfactant. Crop height, lodging, yield and quality of the harvested crop were assessed. Physicochemical properties of spray solution were measured. Adjuvants improved the biological activity of both, CCC and prohexadione-calcium, especially when reduced doses were applied. Efficacy of the plant growth regulators used at normal rate without adjuvant and at reduced rates with adjuvants was similar. Break-Thru S-240 increased the efficacy of CCC and prohexadione-calcium more compared to Adpros 85 SL measured in terms of reduction of plant heigh.

The effects of a microbial inoculant (Thervelics®: a mixture of cells of Bacillus subtilis C-3102 and carrier materials) on rice (Oryza sativa cv. Milkyprincess) and barley (Hordeum vulgare cv. Sachiho Golden) were evaluated in four pot experiments. In the first and second experiments, the dry matter production of rice and barley increased significantly by 10–20% with the inoculation of the mixture at a rate of 107 cfu ⋅ g–1 soil compared with the non-inoculated control. In the third experiment, the growth promoting effects of the mixture, the autoclaved mixture and the carrier materials were compared. The dry mater production of rice grains was the highest in the mixture, and it was significantly higher in the three treatments than in the control, suggesting that the carrier materials may also have a plant growth promoting effect and the living cells might have an additional stimulatory effect. To confirm the efficacy of the living cells in the mixture, only B. subtilis C-3102 cells were used in the fourth experiment. In addition, to estimate the mechanisms in growth promotion by B. subtilis C-3102, three B. subtilis strains with similar or different properties in the production of indole-3-acetic acid (IAA), protease and siderophore and phosphatesolubilizing ability were used as reference strains. Only B. subtilis C-3102 significantly increased the dry matter production of rice grains and the soil protease activity was consistently higher in the soil inoculated with B. subtilis C-3102 throughout the growing period. These results indicate that the microbial inoculant including live B. subtilis C-3102 may have growth promoting effects on rice and barley.

Plant growth-promoting rhizobacteria (PGPR) isolated from the rhizosphere soil of eight field crops at different locations in Egypt were identified. Rhizobacteria strains were identified as Bacillus endophyticus AW1 5, B. filamentosus EM9, ET3, Micrococcus luteus KT2, FW9, FC13, SaW4, Enterobacter cloacae SK18, Pseudomonas azotoformans TPo10, Citrobacter braakii TC3. All isolates solubilised insoluble phosphate and produced IAA, while only six were able to produce siderophores in vitro. Vegetative growth and yield of wheat cv. ‘Sakha 94’ were enhanced after the application of single inoculation of each isolate compared to the control. Grain yield was increased by 20.7– 96.5% over the control according to bacterial isolates. Available phosphorus (P) and counts of total bacteria in soil were observed to be significantly increased in treatments than in control. After the wheat harvest, soil pH was observed to be decreased, and a highly significant negative correlation was observed between soil pH and the levels of available phosphorus. Significant increases in grain and straw yields, as well as uptake of nitrogen (N) and P by plants, were observed due to inoculation with PGPR isolates. Levels of photosynthetic pigments, free amino acids, free phenolics, and reducing sugars in flag leaf and spikes were significantly enhanced by the application of all PGPR isolates compared to the control. Thus this study identifies the PGPR isolates for the improvement of the growth, yield, and quality of wheat. The study may be also useful for field evaluation under different soils and environmental conditions before generalising PGPR isolates as biofertilisers.

Globally more than 5.2 billion hectares of farming fields are damaged through erosion, salinity and soil deterioration. Many salt stress tolerant bacteria have plant growth promoting (PGP) characteristics that can be used to overcome environmental stresses. Isolation and screening of salt-tolerant endophytes from Salicornia brachiata were achieved through surface sterilization of leaves followed by cultivation on 4% NaCl amended media. Performance of isolates towards indole-3-acetic acid (IAA) production, phosphate solubilization, ACC deaminase activity, ammonia production, siderophore production and stress tolerance were determined. On the basis of the highest plant growth promoting activity, SbCT4 and SbCT7 isolates were tested for plant growth promotion with wheat and maize crops. In the present study, a total of 12 morphologically distinct salt-tolerant endophytic bacteria was cultured. Out of 12 isolates, 42% of salt-tolerant endophytes showed phosphate solubilization, 67% IAA production, 33% ACC-deaminase activity, 92% siderophore production, 41.6% ammonia production and 66% HCN production. A dendrogram, generated on the basis of stress tolerance, showed two clusters, each including five isolates. The bacterial isolates SbCT4 and SbCT7 showed the highest stress tolerance, and stood separately as an independent branch. Bacterial isolates increased wheat shoot and root dry weights by 60–82% and 50–100%, respectively. Similarly, improved results were obtained with maize shoot (27–150%) and root (80–126%) dry weights. For the first time from this plant the bacterial isolates were identified as Paenibacillus polymyxa SbCT4 and Bacillus subtilis SbCT7 based on phenotypic features and 16S rRNA gene sequencing. Paenibacillus polymyxa SbCT4 and B. subtilis SbCT7 significantly improved plant growth compared to non-inoculated trials.

Rice blast is one of the most destructive rice diseases known to cause considerable yield losses globally. Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are closely associated with rice plants and improve plant growth and health. To determine how isolated bacteria trigger rice growth, an assessment of phosphate solubilization and auxin production mechanisms was carried out in vitro and in vivo. In this study, the interactions between PGPR and Rhizophagus irregularis were evaluated in wildtype and CYCLOPS mutant plants to provide a sustainable solution against blast disease and reduce the amount of yield loss. Importantly, Bacillus subtilis UTSP40 and Pseudomonas fluorescens UTSP50 exhibited a suppressive effect on AMF colonization which shows the probable existence of a functional competition between AMF and PGPR to dominate the rhizosphere. On the other hand, R. irregularis decreased the biocontrol activity of B. subtilis UTSP40 in wild type, although this reduction was not significant in mutant plants. Results showed that the same defense-related genes were induced in the roots of wild type colonized by B. subtilis UTSP40 and R. irregularis. Therefore, plant cell programs may be shared during root colonization by these two groups of beneficial microorganisms.

The role of the tea commodity in the economy of Indonesia is quite strategic. Various types of microorganisms in nature have been known to increase the benefit of the root function, suppress disease, and accelerate plant growth. This study aimed to determine the potential of indigenous bacteria (Azoto II-1, Acinetobacter sp., bacteria Endo-5, bacteria Endo-65 and Endo-76) on the growth of tea plants and their potential in increasing resistance to blister blight disease. The test of microbes’ potential effect on growth and blister blight was conducted in Gambung, West Java in an experimental field using a randomized block design (RBD) with six treatments and each treatment was replicated four times. The composition of the treatments was: A) Endo-5; B) Endo-65; C) Endo-76; D) Azoto II-1; E) Acinetobacter sp.; and F) control (without microbes). Bacterial suspension was applied directly to the soil at a dose of 2 l · ha−1. The bacterial suspension was applied six times at 1 week intervals. The results of field observations indicated that the intensity of blister blight decreased in all treatments but did not significantly differ from the control. Meanwhile, the results of Acinetobacter sp. treatment in tea shoots was 17.26% higher than the control.

Rare and endemic plant species represent important components of plant biodiversity which require protection to ensure their sustainable conservation. Cerastium banaticum (Rochel) Heuff. is such an endemic and rare species from Romania, for which the genetic variability of two natural populations was studied by SSR markers. Shannon’s information index revealed low levels of genetic diversity in both populations (I = 0.296). As the first attempt in a conservation program a reproducible micropropagation protocol was established starting from seeds, followed by multiplication, rooting, and ex vitro acclimatization. Among the various plant growth regulators tested the highest multiplication coefficient was achieved on a culture medium with 0.5 mg L-1 6-furfurylaminopurine (K) and 1 mg L-1 α-naphthaleneacetic acid (NAA). On this PGRs concentration a number of 26.6 shoots/individual explant with a mean length of 7.9 cm for new generated shoots was registered. The highest number of roots/individual initiated shoot was 2.6 and it was recorded on a culture medium with 0.5 mg L-1 2-isopentyl-adenine (2iP) and 0.1 mg L-1 NAA. The outdoor acclimatization was successfully performed in a specially designed rocky area in the ‘Alexandru Borza’ Botanical Garden, Cluj-Napoca (Romania).

The genus Narcissus has several endemic, rare and/or threatened species in the Iberian Peninsula and North Africa. In vitro propagation is a useful tool for threatened plants conservation used in ex situ strategies. Thus, the aim of this work was to study the propagation in vitro of bulb scale explants of five endemic, rare and/or endangered Narcissus species from the Iberian Peninsula, treated with different PGR combinations. Initiation was achieved in half-strength Murashige and Skoog (MS) basal salts and vitamins, 10 g/L sucrose, 500 mg/L casein hydrolysate, 2 mg/L adenine, 10 mg/L glutathione and 5.5 g/L plant agar. In the multiplication phase, the highest bulblet proliferation was obtained in MS medium supplemented with 30 g/L sucrose and the combination of 10 μM 6-Benzylaminopurine (BAP) + 5 μM α-Naphthaleneacetic acid (NAA) in N. alcaracensis, N. eugeniae and N. hedraeanthus; 20 μM BAP + 5 μM NAA in N. jonquilla and N. yepesii. The highest rooting was obtained with 5 μM NAA + 1 μM Indole-3-butyric acid (IBA) for all species (>75%) and more than 80% of the produced bulblets were successfully acclimatized.

The study was carried out to investigate the interactive effects of exogenous melatonin and excess amounts of zinc and copper on the growth and physiological parameters, antioxidant defense system and nutritional balance of cannabis seedlings. Cannabis sativa L. plants, grown under a completely randomized design, were irrigated with complete Hoagland’s nutrient solution. CuSO ₄ (0, 50 and 150 µM) and ZnSO ₄ (0, 50 and 100 µM) and their combinations were supplied to 21-day-old seedlings for 2 weeks. During the second week, melatonin was added to the nutrient solution at 100 μM. Zn and Cu stress led to reduced growth and physiological parameters, it promoted oxidative stress, changes in antioxidant enzymes activity and imbalance of mineral nutrients in cannabis seedlings. However, melatonin alleviated the growth retardation and physiological disorders of seedlings under normal conditions and heavy metal stress. The content of reduced glutathione and the activity of antioxidant enzymes such as glutathione reductase and ascorbate peroxidase were improved by melatonin. Excess amounts of zinc and copper changed the pattern of nutritional elements distribution in cannabis seedlings. Cu and Zn caused reduced content of Fe, Ca and K ions in shoots and roots. Melatonin treatment was able to adjust the nutrients content in metal-stressed seedlings up to the level of the control. Exogenous melatonin reduced toxic levels of Cu and Zn in seedlings overloaded with copper and zinc. MT also raised K, Ca and Fe concentrations in roots and shoots of seedlings under stress. Our results support the idea that melatonin acts as a powerful antioxidant, it can also be considered as a potent regulator of ion homeostasis in cannabis seedlings under heavy metal toxicity. Further studies still need to investigate the alleviatory effects of melatonin under field conditions.

The aim of the research was to analyze the degree of infection of winter wheat by fungal diseases and to evaluate the morphological and physiological parameters of plants depending on varied foliar fertilization (with and without the ionic form of silver) and applied plant protection agents (active ingredients: propiconazole, fenpropidin, azoxystrobin) in the 2016/2017, 2017/2018 and 2018/2019 growing seasons. The results showed that micronutrient fertilizers with silver and pesticides reduced the severity of fungal diseases better than the control. In most cases, foliar fertilizers enriched with the ionic form of silver at a dose of 1 and 2 l · ha ⁻¹ were the most effective. Moreover, foliar fertilization and pesticides had a positive effect on the morphology of wheat. Combined treatment (micronutrient fertilizer with silver and pesticide at a dose of 1 l · ha ⁻¹) increased stalk length and weight, ear weight and thousand grain weight to the greatest extent in comparison to the other treatments, while the pesticides stimulated ear length the most. In turn, microelement fertilizers with silver at a dose of 1 and 2 l · ha ⁻¹ were better in terms of flag leaf length. Wheat treated with foliar fertilizer and pesticide significantly improved the chlorophyll content based on the leaf greenness index (SPAD). It was found that the foliar application of microelements with silver is promising for use in agriculture because they controlled fungal diseases and ensured the good condition of plants more effectively than pesticides harmful to the environment.

Tubercle disease or a bacterial pocket disease of sugar beets are names used to describe one of the gall-malformed diseases of sugar beet roots. Xanthomonas beticola is the historical name of the pathogen supposedly causing bacterial pocket disease. There were no isolates deposited in any collection corresponding to the originally isolated bacteria, except two strains from the NCPPB (National Collection of Plant Pathogenic Bacteria, UK). However, both isolates were identified as related to Bacillus pumilus, which raised doubts about their pathogenicity. In our laboratory, greenhouse, and preliminary field experiments, we demonstrated that such strains are not pathogenic to sugar beets. Furthermore, both strains promoted their growth, improved their yield quality, and partly protected them against Rhizoctonia solani in a field experiment.

Salinity is one of the most significant constraints to crop production in dry parts of the world. This research emphasizes the beneficial effects of plant growth-promoting rhizobacterial isolates (PGPR) on the physiological responses of maize and wheat in a saline (NaCl) environment. Soil samples for the study were collected from a maize field in Baddi, Himachal Pradesh, India. Isolated bacterial strains were screened for salt (NaCl) tolerance and plant growth-promoting characters (i.e., indole acetic acid (IAA) production, siderophore production, amino cyclopropane-1-carboxylic acid (ACC) deaminase activity, hydrogen cyanide (HCN) production, and mineral phosphate solubilization). Screened bacterial isolates were further tested in pot experiments to examine their effects on wheat and maize growth. The treatments included five levels of bacterial inoculation (P0: control, P1: ACC deaminase positive + siderophore producer + NaCl tolerant bacteria, P2: mineral phosphate solubilizer + HCN producer + NaCl tolerant bacteria, P3: IAA producer + ACC deaminase positive + NaCl tolerant bacteria, P4: bacterial consortium, P5: Phosphomax commercial biofertilizer) and salt stress at 6 dS/m. Research findings found that exposure to a bacterial consortium led to the highest growth parameter in maize, including shoot length, root length, shoot and root dry weight followed by P2, P3, and P5 treatments at 6 dS/m salinity levels. However, P2 showed the best results for wheat at the same salinity levels, followed by P3, P4 and P5 treatments. P1 treatment did not show a significant result compared to control at 6dS/m salt level for both crops. The maximum proline content in maize and wheat was observed in P4 (23.28 μmol · g−1) and P2 (15.52 μmol · g−1) treatments, respectively, followed by P5 with Phosphomax biofertilizer. Therefore, the study proposed the application of growth-promoting bacterial isolates as efficient biofertilizers in the Baddi region of Himachal Pradesh, India.