جستجوی مقالات مرتبط با کلیدواژه "endophytic bacteria" در نشریات گروه "کشاورزی"

alfalfa with the scientific name Medicago sativa is the most important fodder plant in Iran and many parts of the world. This plant is known as the queen of fodder plants due to its high nutritional value and the possibility of planting in different climates. The aim of the current research is to isolate and identify endophytic bacteria from alfalfa roots and investigate their antagonistic effects on human pathogenic bacteria.
The sterilized alfalfa root pieces, after being crushed, were cultured in Tyoglycollate Broth and Muller Hinton Broth liquid culture media for enrichment. After liquid cultures, culture was done on Muller Hinton agar, eosin methylene blue and McConkey agar. Endophytic bacteria were identified by gram staining method and biochemical tests. The antagonistic activity of isolated bacteria was investigated by steric crossing and bilayer methods. From the bacteria with antagonistic effects, DNA extraction was performed and with the use of universal primer, 16SrRNA gene was amplified. The PCR product was sequenced and a phylogeny tree was drawn.
The results showed that alfalfa endophyte bacteria had antagonistic activity and finally, two endophytes were investigated in terms of molecular identity, which belonged to Enterobacter and Pseudomonas genera.
Based on the results, endophytic bacteria have a great diversity and significant antibacterial effects.

Endophytes are microorganisms (bacteria or fungi or actinomycetes) that reside inside the internal tissues of plant with no negative effect on host plants. Endophytic bacteria trigger many positive effects on host plants. The aroma and flavor of strawberry fruit are important characteristics that is affected by endophytic bacteria such as Methylobacterium. Endophytic bacteria, are effective in the synthesis of carotenoids and the production of volatile and phenolic compounds. In addition, they are effective in producing the aromatic components in fruit. Endophytic bacterial frequency and genotype can be affected by host plant genotype, climatic and soil conditions. This study was carried out to isolate endophytic bacteria from two strawberry cultivars (Kurdistan and Parous) in three regions (Angouzan, Gavrood and Noshur) in Kurdistan province. For accurate identification of bacterial isolates, 16S-rRNA gene sequencing was used for identification of purified endophytic isolates and their frequency determined at different times of fruit ripening. The results revealed that the all endophytic bacterial isolates from both cultivars were belong to the genus Methylobacterium. The frequency of these bacteria was statistically different in two cultivars and in different sampling time. The frequency of Methylobacterium significantly was higher in Kurdistan cultivar compared to Parous cultivar in all three regions (p <0.05). The highest frequency of Methylobacterium was observed in the fruit ripening time. It seems that Methylobacterium and its frequency probably have an effect on the aroma and delicacy of these two varieties.

Bacterial wilt disease caused by Ralstonia solanacearum is one of the most destructive diseases in the world, including Kurdistan province of Iran. Using the endophytic bacteria is one of the most effective and applicable methods to control of the disease. In this study, Bacillus sp. Bp91 which was isolated from potato fields in Kurdistan province was used as a superior antagonist against R. solanacearum. The results of the supplementary tests showed that the production of protease in the mentioned strain is positive. This was negative and relatively weak for hydrogen cyanide and siderophore production, respectively. The phylogenetic tree derived from 16S rRNA gene sequence showed the stain belongs to the genus Bacillus sharing the highest level of sequence homology with to B. pumilus. Metabolic studies by GC-mass were also indicated that the two metabolites Eicosane and Dibutyl phthalate are the most prominent antimicrobial metabolites produced by the bacterium.

In this study, three nonpathogenic endophytic bacterial isolates recovered from Fragaria × ananassa stolon and petal and their antagonistic activity was evaluated against Colletotrichum nymphaeae, the causal agent of strawberry anthracnose under in vitro, in vivo, and greenhouse conditions. Bacterial isolates were identified as Bacillus spp. using a combination of phenotypic, biochemical properties and molecular phylogenetic analysis of the 16S rDNA gene sequence. The living cells of bacterial isolates inhibited the mycelial growth of C. nymphaeae using dual culture method and inhibition percentage was evaluated as 41.87, 50, and 54.92 % in MarG2, MarD40 and MarD35, respectively. The volatile compounds (VOCs) produced by bacterial isolates inhibited the mycelial growth of C. nymphaeae and the highest inhibition was observed in MarD35 isolate (24.7%). Moreover, the cell free culture filtrates of bacterial isolates reduced the mycelial growth and conidial germination of pathogen and the highest inhibition was observed in MarG2 (34.96%) on mycelial growth and in MarD35 (52.07%) on conidial germination. The living cells of bacterial isolates decreased anthracnose fruit rot at postharvest and the highest inhibition was observed in MarD40 (85.63%) and MarD35 (81.72%), respectively. Furthermore, disease severity of strawberry anthracnose by bacterial isolates was reduced using drenching soil and plant spraying techniques. The findings of this study showed that bacterial isolates have the ability to prevent the growth of fungal pathogen under in vitro, in vivo and greenhouse conditions.

The present study investigates the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits and their effect on the wheat yield and decreased phosphorus (P) fertilizer use. To this end, the isolated bacteria have been first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then the bacteria have been tested for their ability to dissolve inorganic and organic phosphates. In further laboratory studies, a factorial experiment has been conducted as a randomized complete block design with three replications over two-year field study (2017 and 2018). Experimental treatments include biological and chemical phosphorus fertilizer, the former with two levels (with and without bacterial inoculation) and latter (as the second factor) from triple super phosphate source with five (0%, 25%, 50%, 75%, and 100% of the full recommended fertilizer rate). Results from this experiment prove that supplementing 75% of the recommended P-fertilizer rate with bacterial isolates (co-inoculation with rhizospheric and endophytic bacteria) increases wheat growth indices and yield (747.40 g m-2), which are statistically equivalent to the full fertilizer rate without them. Based on these results, it is suggested that biofertilizer can be used as a fertilizer supplement to reduce the level of fertilizer use but cannot be a substitute for phosphorus fertilizer.

In this study the possibility of inducing resistance was tested using five endophytic bacterial strains against wheat take–all disease caused by the Gaeumannomyces graminis var. tritici (Ggt) under greenhouse conditions. The results showed that disease severity in treated plants compared to control samples decreased 56.6% and wheat resistance against the pathogen has been substantially increased. Effect of five endophytic bacterial strains including Pseudomonas fluorescens, Serratia marcescens, Microbacterium phyllosphaerae, Bacillus pumilus and Streptomyces argenteolus were studied on some enzymes related to plant resistance at the 0, 24, 48 and 168 hours after inoculation with Ggt. Results showed the highest levels of the β–1, 4–glucanase and chitinase at 48 and 168 hours after inoculating of pathogen. The level of β–1, 4–glucanase in plant samples inoculated with Serratia marcescens showed 0.0291 U/mg protein compared to c+ (healthy control without endophytic bacteria and pathogen) with 0/0055 and cp (pathogen– infected control and untreated with endophytic bacteria ) with 0/0075. The level of chitinase for plant samples inoculated with Pseudomonas fluorescens and Serratia marcescens strains were 0.0056 and 0.0045 U/mg protein compared to c+ (healthy control without endophytic bacteria and pathogen) with 0/0030 and cp (pathogen– infected control and untreated with endophytic bacteria) with 0/0031, respectively.

Background and Objectives:

 Khuzestan is the only province with sugarcane cultivation. One of the limiting factors in the production of this crop is the occurrence of frost damages in some years. Since no comprehensive research has yet been conducted on detection and evaluation of bacteria with the potential to form nuclear ice in frostbite, this study was carried out to evaluate this subject.

 Materials and Methods:

 This study was carried out in the laboratory of Institute for Research and Training of Sugar and Auxiliary Industries. Endophytic and epiphytic strains of bacteria were isolated from sugarcane. To test the freezing potential of representative strains, four tests including, "determination of Ice nucleation activity by freezing in the tube", "freezing droplet test at -20 °C", "Ice nucleation test on sugarcane cut leaves in vitro" and "Ice nucleation test on sugarcane plant in greenhouse conditions" were performed. Also the genes of the nucleus were detected by 3076f / 3463r and 3308f / 3463r specific primers. 

Results:

 Results show that bacteria species B. gladioli, B. fungorum, B. cantaminans, M. huakuii, O. ciceri, M. proteolyticum, M. Foliorum, R. solanacearum , R. picketii and X. campestris had different degrees of symptoms. In addition, the genes of the nucleus were detected by 3076f / 3463r and 3308f / 3463r specific primers. For all of above mentioned bacterial strains, specifically strain X. campestris, no references have been reported of ice nucleation activity. To assess susceptibility or resistance of sugarcane, cultivar CP69-1062 were the most susceptible and highly damaged in the tests including "Ice nucleation test on sugarcane cut leaves in vitro" and "Ice nucleation test on sugarcane plant in greenhouse conditions". In addition, CP57-614 and CP48-103 cultivars showed minimum variation in frosting in compression to CP69-1062 cultivar. Two cultivars including CP73-21 and SP70-1143 exhibited a high degree of resistance to frostbite.

 Discussion:

 Due to the high variation among Ice-Nucleating bacteria and the sensitivity of commercial cultivars, our finding can be a suitable option for producers and encourage them to use resistant cultivars in the field.

Ralstonia solanacearum is the cause of tomato bacterial wilt. Under favorable environmental conditions, it can cause rapid wilt and a lot of damage, and there is no practical remedy for it. The aim of this study was to separate endophytic bacteria B. cepacia from tomato stems of local cultivar and then to study the biocontrol effect of this bacteria against the bacterial wilt of tomatoes.
In this study four endophytic bacteria from tomato stem were isolated. Then after identification with bacteriology standard tests in order to investigation of their antagonistic effect and also effect on the growth rate of the plant in vitro with seed diffusion agar method were examined. Result of biochemical tests showed that all of endophytic bacteria which isolated from tomato stem were B. cepacia. In in vitro condition on the seed with B. cepacia bacteria in medium containing R. solanacearum bacteria showed the formation of 2- to-4.5 –mm haloes. In greenhouse conditions, these bacteria caused a suppression of the disease by about 60% and a significant increase in tomato plants, and a significant difference with the control was observed.

Root-Knot nematode, Meloidogyne javanica is currently proposed as an important problem in the cucumber greenhouses of the country. In the present study, endophytic bacteria were evaluated to control the root-knot nematode.Seventy strains were isolated from cucumber roots, gathered from fields and greenhouses in Razavi Khorasan province.Based on the results of biological assays, seven representative strains showing the highest values of second instar larvae mortality and inhibition of egg hatching, were selected for greenhouse experiments. These bacterial strains were examined in terms of reduction of pathogenicity indexes and disease severity. Strains Fm1, Em1 and Y15 were evaluated significantly positive in reduction of egg, gall and second instar larvae number on infected cucumber roots. Moreover, the lowest level of gall index was obtained following the application of these strains compared to the control (only nematode). According to 16S rDNA gene sequencing, three selected strains associated to greenhouse trials belonged to Pseudomonas rhodesiae (Fm1 and Em1) and Acinetobacter sp. (Y15). Consequently, strains Fm1, Em1, and Y15 can be suggested as sufficient candidates in order to perform more studies on the root knot nematode repression in natural conditions.

Some bacteria are capable of entering the plant as endophytes that do not cause harm and could establish a mutualistic association with host plants. Endophytic bacteria are bacteria that live in plant tissues without doing substantive harm. They enter plant tissue primarily through different plant zones. Both Gram-positive and Gram-negative bacteria have been isolated from several tissue types in several plant species. In addition, several different bacterial species have been isolated from a single plant. Variation in endophytic bacteria populations referred to the time of sampling, type of plant tissue, age and environment conditions, as well. In general endophytic bacteria occur at lower population densities than rhizospheric bacteria or bacterial pathogens. Endophytic populations, like rhizospheric populations, are conditioned by biotic and abiotic factors, but endophytic bacteria could be better protected from biotic and abiotic stresses than rhizospheric bacteria. It is clear that the interaction between plants and some endophytic bacteria is associated with beneficial effects such as plant growth promotion and biocontrol potential against plant pathogens. These types of bacteria are often capable of eliciting significant physiological changes that modulate the growth and development of the plant. Most of the time, these beneficial effects of endophytes are greater than those of many rhizosphere-colonizing bacteria. Endophytic bacteria affect bacterial growth by numerous mechanisms directly or indirectly. Some genus of bacteria such as Azosprillium, Enterobacter, Azotobacter and Pseudomonas produces plant growth regulators which lead to plant growth improvement. Microorganism profit from plants due to the enhanced availability of nutrients, whereas plants can receive benefits from bacterial associates by growth enhancement or stress reduction. Therefore, mutualistic interactions between host plants and associated microorganisms could have emerged as a result of the clear positive selection exerted on these associations. The current study is conducted in order to evaluate the effectiveness of cucumber root endophytic bacteria on increasing plant growth indexes.
In this study, 45 strains were isolated from cucumber roots as mentioned in the literature. In the first step, all of them subjected to seed germination assay in lab conditions. Furthermore, they are evaluated for vigor index according to references. Seven strains (En 1 to En7) are selected for complementary research in greenhouse trials using randomized block design with 4 repetitions. Statistical analysis is done using SPSS v.22 by Duncan methods under 5% possibility levels. To detect preferred bacterial species, 16S rDNA-PCR product is sent for sequencing to Macrogen, Korea. The sequences are checked in BLAST program in NCBI database.
Based on medians comparison, cucumber seed cultivar Negin, are treated by 45 endophytic bacteria separately. Among them, seven strains showed a significant difference at 1% possibility level in comparison to control. These strains presented high vigor index from 1954.6 to 572 compared to control. They also showed better seed germination percentage rather than control in the range of 95 to 45 %, and selected for greenhouse trials. The results of medians comparison in pot experiments demonstrated that En1 strains leads to 60% root and shoot length enhancement comparing to control. Furthermore, highest shoot (84.6%) and root (55.8%) wet weight are recorded for En6 in comparison to control. Molecular data revealed that strains En1 and En6 belonging to Acinetobacter sp. and Pseudomonas rhodesiae, respectively. It is known that variation in endophytic bacteria may reflect differences in agriculture management methods. The P. rhodesiae is categorized in Pseudomonas fluorescent group and is isolated from mineral water for the first time. The positive effect of P. rhodesiae on different agricultural crops such as tomato, paper and wheat is reported. Genus Acinetobacter has an ability to produce plant hormones which changes plant chemical function towards growth improvement. One strain of this genus causes enhancement of sugar beet dry and wet weight to 19 and 69 % respectively, more than control treatment. More studies show that auxin production, phosphate solubilization, and nitrogen fixation are related to plants growth increasing. Since these entophytic bacteria have the effective role in inorganic materials increasing, application of this genus as biological fertilizer is suggested.
Based on our data, En1 and En6 isolates speed up seed germination and increase cucumber growth parameters. Complementary surveys concerning the application of these isolates as separate or combined samples under greenhouse and field conditions are recommended. This is the first report of isolation of Pseudomonas rhodesiae and Acinetobacter sp. as endophytic bacteria from cucumber in Iran.