Both biotic and abiotic stresses are major constrains to agricultural production. Under stress conditions, plant growth is affected by a number of factors such as hormonal and nutritional imbalance, ...ion toxicity, physiological disorders, susceptibility to diseases, etc. Plant growth under stress conditions may be enhanced by the application of microbial inoculation including plant growth promoting rhizobacteria (PGPR) and mycorrhizal fungi. These microbes can promote plant growth by regulating nutritional and hormonal balance, producing plant growth regulators, solubilizing nutrients and inducing resistance against plant pathogens. In addition to their interactions with plants, these microbes also show synergistic as well as antagonistic interactions with other microbes in the soil environment. These interactions may be vital for sustainable agriculture because they mainly depend on biological processes rather than on agrochemicals to maintain plant growth and development as well as proper soil health under stress conditions. A number of research articles can be deciphered from the literature, which shows the role of rhizobacteria and mycorrhizae alone and/or in combination in enhancing plant growth under stress conditions. However, in contrast, a few review papers are available which discuss the synergistic interactions between rhizobacteria and mycorrhizae for enhancing plant growth under normal (non-stress) or stressful environments. Biological interactions between PGPR and mycorrhizal fungi are believed to cause a cumulative effect on all rhizosphere components, and these interactions are also affected by environmental factors such as soil type, nutrition, moisture and temperature. The present review comprehensively discusses recent developments on the effectiveness of PGPR and mycorrhizal fungi for enhancing plant growth under stressful environments. The key mechanisms involved in plant stress tolerance and the effectiveness of microbial inoculation for enhancing plant growth under stress conditions have been discussed at length in this review. Growth promotion by single and dual inoculation of PGPR and mycorrhizal fungi under stress conditions have also been discussed and reviewed comprehensively.
•Plant growth under stress conditions•Strategies to mitigate the adverse effects of stresses on plants•Role of plant beneficial bacteria and mycorrhizae for plant adaptation to stress•Effectiveness of combined inoculation of PGPR and mycorrhizal fungi•Discussion on recent developments in PGPR–mycorrhizae–plant interactions under stress
The present study was carried out to evaluate the antagonistic efficacy of
Aspergillus versicolor
against the soil and seed inhibiting destructive plant pathogen
Macrophomina phaseolina
. The tested ...antagonist was confirmed by rDNA sequencing of ITS and β-tubulin genes with respective accession numbers MN719083 and MN736397. In dual culture bioassays,
A. versicolor
showed potent antagonist activity and reduced the pathogen’s growth by 60% over control. To understand the mechanism of antagonistic fungus, DNA of the pathogenic fungus was incubated in secondary metabolites produced by the
A. versicolor
for 24 and 48 h. After 48 h, metabolites of
A. versicolor
fully degraded the DNA of
M. phaseolina
. Moreover, for the identification of bioactive compounds, the chloroform and ethyl acetate fractions of
A. versicolor
culture filtrates were subjected to GC–MS analysis. A total of 10 compounds were identified in each of the two fractions. Among these, chondrillasterol (37.43%) followed by 1,2-benzedicarboxylic acid, diisooctyl ester (25.93%), decane (16.63%), 9,12-octadecadienoic acid (Z,Z)- (13.32%), stigmasterol (11.16%), undecane (10.93%),
cis
-1-chloro-9-octadecene (8.66%), benzene, 1,3,5-trimethyl (8.46%), and hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester (8.13%) were the major compounds. Some of the identified compounds are known to possess strong antifungal, antibacterial, nematicidal, and antioxidant properties. The present study concludes that
A. versicolor
is an effective antagonist against
M. phaseolina
.
Background
Sclerotium rolfsii
is a soil-borne fungal pathogen causing diseases in more than 500 plant species. It causes southern blight disease in chili. Chemical fungicides are used to control this ...disease, which also pollute the environment. The present study was designed to assess the potential of two species of plant-growth-promoting rhizobacteria (PGPR) viz.
Bacillus megaterium
and
Pseudomonas fluorescence
, and an allelopathic weed,
Anagallis arvensis
L., for the control of southern blight disease of chili.
Results
Initially, three PGPR strains, viz.
B. megaterium
OSR3,
B. megaterium
ZMR6, and
P. fluorescence
PF-097, were selected for their in vitro antagonistic assessment against
S. rolfsii
by dual culture technique on potato dextrose agar medium. OSR3 showed the highest antagonistic potential (68%), followed by PF-097 (54%) and ZMR6 (33%)
.
In a pot experiment, the two best strains of PGPR, namely OSR3 and PF-097, and dried biomass of
A. arvensis
(DBA) in different concentrations (1, 2 and 3%) were used to manage southern blight disease of chili
.
In positive control treatment (
S. rolfsii
only), plant survival was low (73%) than the negative control (100%). OSR3, PF-097, OSR3 + 2% DBA, and PF-097 + 2% DBA significantly enhanced plant survival over positive control. The highest increase in chili growth over positive control was recorded due to OSR3, followed by PF-097 inoculations. Contents of carotenoid and chlorophyll were significantly decreased due to the fungal pathogen and improved due to PGPR strains. Application of the two PGPR strains and different concentrations of
A. arvensis
distinctly increased the catalase (CAT), peroxidase (POX), and polyphenol peroxidase (PPO) activities over positive control.
Conclusions
The present study concluded that PGPR strains
B. megaterium
OSR3 and
P. fluorescence
PF-097 can control southern blight disease effectively and increase growth and yield of chili.
Contamination of agricultural soil with chromium (Cr) ions has threatened global crop, human and ecosystem health. Its two oxidation states viz. Cr(III) and Cr(VI) are most stable and readily ...available to the plants. The study explored the impact of increasing exposure (up to 500 ppm) of Cr(III) and Cr(VI) on bio-physical traits of 15-day-old seedlings (in vitro) as well as 60-day-old tomato plant (in vivo), and highlighted the importance of buffel grass (Cenchrus pennisetiformis) in mitigating Cr levels in the tomato plants. In vitro, Petri plate bioassays with 13 different concentrations (20-500 ppm) of Cr(III) and Cr(VI) depicted the highly toxic effect of metal ions ≥ 200 ppm on all bio-physical traits of tomato seedlings. In vivo, soil spiked with Cr(III) and Cr(VI) (200, 300, and 400 mg/kg) was amended with 1% and 2% dry biomass of buffel grass. Phytotoxicity was higher in Cr(VI)-spiked soil compared with Cr(III)-spiked soil. Cr was mainly accumulated in tomato roots, and more Cr was translocated from roots to shoots from Cr(VI)-spiked soil than Cr(III)-spiked soil. Soil amendments with 2% weed biomass reduced metal toxicity in plants, particularly at 200 and 300 mg/kg of Cr. Protein profiles through SDS-PAGE revealed 12-50 kDa (mainly PR proteins) as an important region in tomato leaf, where many new bands were expressed under different treatments, particularly in the treatments provided with buffel grass. PCA-based biplot clearly separated Cr tolerance treatments from highly sensitive treatments. For the cultivation of tomato plants in Cr(III) and Cr(VI) contaminated soil (200 and 300 mg/kg), the biomass of Cloncurry buffel grass should be considered an effective and easily available phyto-management option.
In the present study,
Mucor fragilis
is reported causing rot of seychelles pole beans (
Phaseolus vulgaris
L.) for the first time from Pakistan. The infected beans were collected from the local ...market of Lahore, Pakistan during 2019. The observed symptoms showed the presence of fluffy and soft fungal mycelium with white to dark brown discoloration that deteriorated the beans quality. The disease incidence was 15%. The fungus was isolated on malt extract agar (MEA) plates and characterized morphologically as well as microscopically as
Mucor fragilis
. For more accuracy, molecular studies were performed by using ITS and EF1 primer pairs. The PCR products obtained were submitted to GenBank under the respective accession numbers MZ351294 and OM801894, respectively. The pathogen was identified as
M. fragilis.
Koch’s postulates confirmed the pathogenicity of
M. fragilis
on seychelles pole beans and the experiment was conducted for three times.
Sclerotium rolfsii
is a soil-borne plant pathogen that causes root diseases in hundreds of plant species. It also causes collar rot disease in chickpea (
Cicer arietinum
L.). The present pot study ...was carried out to investigate the effect of soil amendment with dry biomass of a weed
Chenopodium album
L. and two antagonistic fungi, namely
Trichoderma harzianum
and
T. viride
, on growth and yield of chickpea variety Noor 2009 in soil infected with
S. rolfsii.
The pathogen-contaminated soil was amended either with 1, 2, or 3%
C. album
dry biomass,
T. harzianum
, and
T. viride
alone, or combinations of either of the two
Trichoderma
species and plant dry biomass. The lowest shoot and root dry biomass and grain yield of chickpea were recorded in
S. rolfsii
inoculation alone without any soil amendment (positive control). Plant growth and yield were significantly and gradually increased over positive control with an increase in
C. album
dry biomass application in the soil. Likewise, soil application of either of the two
Trichoderma
species significantly enhanced plant growth and yield over positive control under biotic stress of
S. rolfsii.
Combined application of either
T. harzianum
or
T. viride
with 3% dry biomass of
C. album
also proved highly effective in alleviating biotic stress of
S. rolfsii
on growth and yield of chickpea.
Antifungal activity of Monotheca buxifolia methanolic extract and its various fractions were assessed against Macrophomina phaseolina, a soil-borne fungal pathogen of more than 500 vegetal species as ...well as rare and emerging opportunistic human pathogen. Different concentrations of methanolic extract (3.125 to 200 mg mL
) inhibited fungal biomass by 39-45%. Isolated n-hexane, chloroform and ethyl acetate fractions suppressed fungal biomass by 32-52%, 29-50% and 29-35%, respectively. Triterpenes lupeol and lupeol acetate (1, 2) were isolated from n-hexane while betulin, β-sitosterol, β-amyrin, oleanolic acid (3-6) were isolated from chloroform fraction. Vanillic acid, protocatechuic acid, kaempferol and quercetin (7-10) were isolated from the ethyl acetate fraction and identified using various spectroscopic techniques namely mass spectroscopy and NMR. Antifungal activity of different concentrations (0.0312 to 2 mg mL
) of the isolated compounds was evaluated and compared with the activity of a broad spectrum fungicide mancozeb. Different concentrations of mencozeb reduced fungal biomass by 83-85%. Among the isolated compounds lupeol acetate (2) was found the highest antifungal against M. phaseolina followed by betulin (3), vanillic acid (7), protocatechuic acid (8), β-amyrin (5) and oleanolic acid (6) resulting in 79-81%, 77-79%, 74-79%, 67-72%, 68-71% and 68-71%, respectively. Rest of the compounds also showed considerable antifungal activity and reduced M. phaseolina biomass by 41-64%.
Antifungal activity of Monothecabuxifolia methanolic extract and its various fractions were assessed against Macrophominaphaseolina, a soil-borne fungal pathogen of more than 500 vegetal species as ...well as rare and emerging opportunistic human pathogen. Different concentrations of methanolic extract (3.125 to 200 mg mL−1) inhibited fungal biomass by 39–45%. Isolated n-hexane, chloroform and ethyl acetate fractions suppressed fungal biomass by 32–52%, 29–50% and 29–35%, respectively. Triterpenes lupeol and lupeol acetate (1, 2) were isolated from n-hexane while betulin, β-sitosterol, β-amyrin, oleanolic acid (3–6) were isolated from chloroform fraction. Vanillic acid, protocatechuic acid, kaempferol and quercetin (7–10) were isolated from the ethyl acetate fraction and identified using various spectroscopic techniques namely mass spectroscopy and NMR. Antifungal activity of different concentrations (0.0312 to 2 mg mL−1) of the isolated compounds was evaluated and compared with the activity of a broad spectrum fungicide mancozeb. Different concentrations of mencozeb reduced fungal biomass by 83–85%. Among the isolated compounds lupeol acetate (2) was found the highest antifungal against M.phaseolina followed by betulin (3), vanillic acid (7), protocatechuic acid (8), β-amyrin (5) and oleanolic acid (6) resulting in 79–81%, 77–79%, 74–79%, 67–72%, 68–71% and 68–71%, respectively. Rest of the compounds also showed considerable antifungal activity and reduced M.phaseolina biomass by 41–64%.
Drug resistant tuberculosis (DR-TB) is a major public health problem in developing countries such as Pakistan.
The current study was conducted to assess the frequency of drug resistant tuberculosis ...including multi drug resistance (MDR- TB) as well as risk factors for development of DR-TB, in Punjab, Pakistan.
Drug susceptibility testing (DST) was performed, using proportion method, for 2367 culture positive Mycobacterium tuberculosis (MTB) cases that were enrolled from January 2012 to December 2013 in the province of Punjab, Pakistan, against first-line anti-tuberculosis drugs. The data was analyzed using statistical software; SPSS version 18.
Out of 2367 isolates, 273 (11.5%) were resistant to at least one anti-TB drug, while 221 (9.3%) showed MDR- TB. Risk factors for development of MDR-TB were early age (ranges between 10-25 years) and previously treated TB patients.
DR-TB is a considerable problem in Pakistan. Major risk factors are previous history of TB treatment and younger age group. It emphasizes the need for effective TB control Program in the country.
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