Biostimulant Activity of Azotobacter chroococcum and Trichoderma harzianum in Durum Wheat under Water and Nitrogen Deficiency

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Abstract

Biostimulants hold great potential for developing integrated sustainable agriculture systems. The rhizobacteria Azotobacter chroococcum strain 76A and the fungus Trichoderma harzianum strain T22, with demonstrated biostimulant activity in previous systems, were evaluated in Triticum durum cv Creso for their ability to enhance growth and tolerance to drought stress. Growth and drought tolerance were evaluated in conditions of low and high soil nitrogen, with two levels of water stress. T. harzianum increased plant growth (+16%) under control conditions and tolerance to moderate drought stress (+52%) under optimal fertilization, while A. chroococcum conferred a growth penalty (−28%) in well-watered conditions under suboptimal fertilization and increased tolerance only under extreme drought stress (+15%). This growth penalty was ameliorated by nitrogen fertilization. T. harzianum abundance was found to be positively correlated to extreme soil drying, whereas A. chroococcum-induced tolerance was dependent on soil nitrogen availability. These results indicate that while biostimulants may enhance growth and stress tolerance, nutrient availability soil and environmental conditions heavily influence these responses. These interactions should be considered when designing biostimulant products targeted to specific cultural conditions.

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Most cited references 88

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Role of proline under changing environments: a review.

Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni … (2012)

When exposed to stressful conditions, plants accumulate an array of metabolites, particularly amino acids. Amino acids have traditionally been considered as precursors to and constituents of proteins, and play an important role in plant metabolism and development. A large body of data suggests a positive correlation between proline accumulation and plant stress. Proline, an amino acid, plays a highly beneficial role in plants exposed to various stress conditions. Besides acting as an excellent osmolyte, proline plays three major roles during stress, i.e., as a metal chelator, an antioxidative defense molecule and a signaling molecule. Review of the literature indicates that a stressful environment results in an overproduction of proline in plants which in turn imparts stress tolerance by maintaining cell turgor or osmotic balance; stabilizing membranes thereby preventing electrolyte leakage; and bringing concentrations of reactive oxygen species (ROS) within normal ranges, thus preventing oxidative burst in plants. Reports indicate enhanced stress tolerance when proline is supplied exogenously at low concentrations. However, some reports indicate toxic effects of proline when supplied exogenously at higher concentrations. In this article, we review and discuss the effects of exogenous proline on plants exposed to various abiotic stresses. Numerous examples of successful application of exogenous proline to improve stress tolerance are presented. The roles played by exogenous proline under varying environments have been critically examined and reviewed.

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Trichoderma species--opportunistic, avirulent plant symbionts.

Gary E Harman, Charles R. Howell, Ada Viterbo … (2004)

Trichoderma spp. are free-living fungi that are common in soil and root ecosystems. Recent discoveries show that they are opportunistic, avirulent plant symbionts, as well as being parasites of other fungi. At least some strains establish robust and long-lasting colonizations of root surfaces and penetrate into the epidermis and a few cells below this level. They produce or release a variety of compounds that induce localized or systemic resistance responses, and this explains their lack of pathogenicity to plants. These root-microorganism associations cause substantial changes to the plant proteome and metabolism. Plants are protected from numerous classes of plant pathogen by responses that are similar to systemic acquired resistance and rhizobacteria-induced systemic resistance. Root colonization by Trichoderma spp. also frequently enhances root growth and development, crop productivity, resistance to abiotic stresses and the uptake and use of nutrients.

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Screening of free-living rhizospheric bacteria for their multiple plant growth promoting activities.

Farah Ahmad, Iqbal Ahmad, M S Khan (2008)

Plant growth promoting rhizobacteria (PGPR) are known to influence plant growth by various direct or indirect mechanisms. In search of efficient PGPR strains with multiple activities, a total of 72 bacterial isolates belonging to Azotobacter, fluorescent Pseudomonas, Mesorhizobium and Bacillus were isolated from different rhizospheric soil and plant root nodules in the vicinity of Aligarh. These test isolates were biochemically characterized. These isolates were screened in vitro for their plant growth promoting traits like production of indoleacetic acid (IAA), ammonia (NH(3)), hydrogen cyanide (HCN), siderophore, phosphate solubilization and antifungal activity. More than 80% of the isolates of Azotobacter, fluorescent Pseudomonas and Mesorhizobium ciceri produced IAA, whereas only 20% of Bacillus isolates was IAA producer. Solubilization of phosphate was commonly detected in the isolates of Bacillus (80%) followed by Azotobacter (74.47%), Pseudomonas (55.56%) and Mesorhizobium (16.67%). All test isolates could produce ammonia but none of the isolates hydrolyzed chitin. Siderophore production and antifungal activity of these isolates except Mesorhizobium were exhibited by 10-12.77% isolates. HCN production was more common trait of Pseudomonas (88.89%) and Bacillus (50%). On the basis of multiple plant growth promoting activities, eleven bacterial isolates (seven Azotobacter, three Pseudomonas and one Bacillus) were evaluated for their quantitative IAA production, and broad-spectrum (active against three test fungi) antifungal activity. Almost at all concentration of tryptophan (50-500 microg/ml), IAA production was highest in the Pseudomonas followed by Azotobacter and Bacillus isolates. Azotobacter isolates (AZT(3), AZT(13), AZT(23)), Pseudomonas (Ps(5)) and Bacillus (B(1)) showed broad-spectrum antifungal activity on Muller-Hinton medium against Aspergillus, one or more species of Fusarium and Rhizoctonia bataticola. Further evaluation of the isolates exhibiting multiple plant growth promoting (PGP) traits on soil-plant system is needed to uncover their efficacy as effective PGPR.

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Author and article information

Contributors

Michael James Van Oosten: (View ORCID Profile)

Roberta Marra: (View ORCID Profile)

Sheridan Lois Woo: (View ORCID Profile)

Valerio Cirillo: (View ORCID Profile)

Albino Maggio: (View ORCID Profile)

Journal

Journal ID (publisher-id): ABSGGL

Title: Agronomy

Abbreviated Title: Agronomy

Publisher: MDPI AG

ISSN (Electronic): 2073-4395

Publication date Created: February 2021

Publication date (Electronic): February 20 2021

Volume: 11

Issue: 2

Page: 380

Article

DOI: 10.3390/agronomy11020380

SO-VID: 858a3f59-6f16-4e3b-b1b7-a9aaf8cf3e1e

License:

https://creativecommons.org/licenses/by/4.0/

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