Effect of Azospirillum-mediated plant growth promotion on the development of bacterial diseases on fresh-market and cherry tomato

Abstract

Aims: Plant growth-promoting (PGP) activity of two Azospirillum strains and their effects on foliar and vascular bacterial diseases were evaluated on fresh market and cherry tomato. Methods and Results: Tomato seeds were inoculated with A. brasilense Sp7 or Azospirillum sp. BNM-65. Four-week-old plants were challenge-inoculated with Clavibacter michiganensis subsp. michiganensis (bacterial canker) or with Xanthomonas campestris pv. vesicatoria (bacterial spot). Azospirillum-induced PGP was greater on cherry than on fresh-market tomato. Cherry tomato was more resistant to bacterial canker but more susceptible to bacterial spot than the fresh-market tomato. Canker severity was not affected by Azospirillum seed treatments. However, leaf-and plant-death were delayed on Azospirillum-treated plants compared with nontreated controls. Azospirillum increased the bacterial spot severity on cherry but not on fresh-market tomato. Conclusions: PGP was observed on both tomato genotypes, although growth effects were larger on cherry tomato. Also, Azospirillum treatments may alter tomato susceptibility to bacterial diseases. Significance and Impact of the Study: The interaction between PGP rhizobacteria like Azospirillum spp., not known to induce systemic resistance, with plant pathogens distantly located is frequently overlooked. This work demonstrates the importance of this kind of evaluation.

Effectiveness of Azospirillum brasilense Sp245 on young plants of Vitis vinifera L.

“…It has been established that favorable agro-climatic conditions [22] likely play a key role in determining the nutritional status of the hardwood cuttings, which is an important factor for rooting and plant establishment [23,24,15]. Certainly, the stimulation of the root apparatus in both rootstocks, indicated in primary roots and final root biomass, confirmed previous evidence obtained in other species and grapevine rootstocks [3,7,25]. Moreover, it has been shown that Azospirillum inoculation may also exert strong stimulatory activities in plants, by inducing changes in root architecture provoking a more symmetric root system [8].…”

Azospirillum sp. Strain B510 Enhances Rice Growth and Yield

“…In tomato, A. brasilense Sp7 and Azospirillum sp. BNM-65 exhibited positive effects on shoot and root biomass, however, they enhanced the development of bacterial diseases (14). Treatment with a nitrogen-fixing strain of Azospirillum lipoferum in the root zone of rice plants promoted early tillering and reproductive growth, although the total dry weight and nitrogen content of the rice plants were not markedly increased by the inoculation (18).…”

“…Extensive studies have been conducted to characterize the plant growth-promoting effects of PGPRs including Azospirillum species (3, 5-7, 14, 17), with reports that some of these bacteria produced plant hormones, such as IAA (13), cytokinines (2,8) and gibberellins (1). At present, it is not known whether strain B510 produces plant hormones inside the host to promote its growth, although it may have this ability (1,2,8,14). To our knowledge, as endophytic bacteria, only Azoarcus in rice and Gluconacetobacter in sugar cane have been reported to promote the growth of plants in pots under greenhouse conditions.…”

Azospirillum brasilense Produces the Auxin-Like Phenylacetic Acid by Using the Key Enzyme for Indole-3-Acetic Acid Biosynthesis

“…Nevertheless, the exact mechanisms involved in Azospirillum acting as a putative biocontrol agent are not yet known. Some reports therefore indicate that the protective mechanism may be indirectly explained by the plant growth promotion effect or by outcompeting other bacteria hosted by the same plant (3,46).In the present study, we attempted to further screen A. brasilense supernatant (extracts) for the presence of metabolites (besides IAA), which may be involved in the persistence of Azospirillum in the rhizosphere. This screening led to the identification of phenylacetic acid (PAA), an auxin-like molecule with antimicrobial activity.…”

“…have been identified so far (39,40,50,55,60). However, there have been reports of moderate biocontrol capabilities of Azospirillum brasilense against crown gall disease, bacterial leaf blight of mulberry, and bacterial leaf and/or vascular diseases of tomato (1,3,4,46,54). In addition, A. brasilense can restrict the proliferation of other nonpathogenic rhizosphere bacteria (21).…”