Changes in root morphology of wheat caused by <i>Azospirillum</i> inoculation

Kapulnik, Yoram; Okon, Yaacov; Henis, Y.

doi:10.1139/m85-165

Cited by 142 publications

(79 citation statements)

References 19 publications

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“…Industrial-grade organic acids are available in inexpensive bulk quantities, as they are used regularly by the food industry. Perhaps the yellowish color is a symptom of metabolic inhibition in the host plant caused by the high levels of A. brasilense on the leaves; A. brasilense is known to inhibit the growth of roots at very high concentrations (2,25). Alternatively, this application perhaps induced a minor chlorosis, a common symptom of nutrient stress in plants.…”

Section: Discussionmentioning

confidence: 99%

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Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Bashan¹,

de‐Bashan

2002

Appl Environ Microbiol

122

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Pseudomonas syringae pv. tomato, the causal agent of bacterial speck of tomato, and the plant growthpromoting bacterium Azospirillum brasilense were inoculated onto tomato plants, either alone, as a mixed culture, or consecutively. The population dynamics in the rhizosphere and foliage, the development of bacterial speck disease, and their effects on plant growth were monitored. When inoculated onto separate plants, the A. brasilense population in the rhizosphere of tomato plants was 2 orders of magnitude greater than the population of P. syringae pv. tomato (10 7 versus 10 5 CFU/g [dry weight] of root). Under mist chamber conditions, the leaf population of P. syringae pv. tomato was 1 order of magnitude greater than that of A. brasilense (10 7 versus 10 6 CFU/g [dry weight] of leaf). Inoculation of seeds with a mixed culture of the two bacterial strains resulted in a reduction of the pathogen population in the rhizosphere, an increase in the A. brasilense population, the prevention of bacterial speck disease development, and improved plant growth. Inoculation of leaves with the mixed bacterial culture under mist conditions significantly reduced the P. syringae pv. tomato population and significantly decreased disease severity. Challenge with P. syringae pv. tomato after A. brasilense was established in the leaves further reduced both the population of P. syringae pv. tomato and disease severity and significantly enhanced plant development. Both bacteria maintained a large population in the rhizosphere for 45 days when each was inoculated separately onto tomato seeds (10 5 to 10 6 CFU/g [dry weight] of root). However, P. syringae pv. tomato did not survive in the rhizosphere in the presence of A. brasilense. Foliar inoculation of A. brasilense after P. syringae pv. tomato was established on the leaves did not alleviate bacterial speck disease, and A. brasilense did not survive well in the phyllosphere under these conditions, even in a mist chamber. Several applications of a low concentration of buffered malic acid significantly enhanced the leaf population of A. brasilense (>10 8 CFU/g [dry weight] of leaf), decreased the population of P. syringae pv. tomato to almost undetectable levels, almost eliminated disease development, and improved plant growth to the level of uninoculated healthy control plants. Based on our results, we propose that A. brasilense be used in prevention programs to combat the foliar bacterial speck disease caused by P. syringae pv. tomato.Tomato plants are hosts to Azospirillum brasilense, a plant growth-promoting bacterium (PGPB) (7,8), and Pseudomonas syringae pv. tomato, the causal agent of bacterial speck disease (35,47). This disease is of moderate economic importance to tomato production under greenhouse and field conditions (24). Whereas A. brasilense increases the growth and yield of tomato plants (14), P. syringae pv. tomato decreases production (51). Although A. brasilense is known as a rhizosphere bacterium (7), some strains are ephiphytic (7, 10), and P. syringae pv. tomato is...

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Section: Discussionmentioning

confidence: 99%

“…These concentrations are optimal for plant growth promotion by Azospirillum sp. (14), for avoiding the growth inhibition known to be induced by high cell concentrations (2,25), and for preventing atypical symptom formation caused by high concentrations of P. syringae pv. tomato (12).…”

Section: Methodsmentioning

confidence: 99%

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Bashan¹,

de‐Bashan

2002

Appl Environ Microbiol

122

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“…In order to obtain these plant growth-promoting effects, good colonization of the plant roots by Azospirillum spp. appears to be important (12). It has been shown that Azospirillum spp.…”

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confidence: 99%

Expression of the Agrobacterium tumefaciens chvB virulence region in Azospirillum spp

et al. 1990

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Inner membranes of Azospirillum brasilense incubated with UDP-glucose were unable to synthesize j0-(1-2) glucan and lacked the 235-kilodalton intermediate protein known to be involved in the synthesis of 0-(1-2) glucan in Agrobacterium tumefaciens and Rhizobium meliloti. Inner membranes ofA. brasilense strains carrying a cosmid containing the chromosomal virulence genes chvA and chvB of Agrobacterium tumefaciens formed 03-(1-2) glucan in vitro and synthesized the 235-kilodalton intermediate protein.No DNA homology to the chvB region was found in different wild-type strains of A. brasilense, but the introduction of a cosmid containing the Agrobacterium tumefaciens chvA and chvB regions yielded strains in which DNA hybridization with the chvB region was detected, provided that the strains were grown under an antibiotic selective pressure.

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“…As nitrogen inhibits the nitrogenase enzyme, inoculation with Azospirillum may contribute to yield increases particularly when plant access to mineral nitrogen in the soil is restricted. Upon Azospirillum inoculation an alteration in root morphology was observed, which has been ascribed to the bacterial production of plant growth-regulating substances (Kapulnik et al, 1985;Fallik et al, 1994). Higher nutrient uptake by inoculated roots and the improved water status of the plant could, in turn, be the main factors enhancing plant growth and yield (Okon, 1994).…”

Section: Resultsmentioning

confidence: 99%

Effect of liquid and cyst formulations of Azospirillum with inorganic nitrogen on the growth and yield of rice

Vendan

Thangaraju

2009

Acta Agronomica Hungarica

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The nitrogen-fixing rhizobacterium Azospirillum lives in close association with plant roots, where it exerts beneficial effects on the plant growth and yield of many crops of agronomic importance. As carrier-based inoculants have a short shelf life and poor quality, new liquid and cyst formulations of inoculants have been developed and standardized for Azospirillum. In the present investigation, experiments were conducted to study the effect of liquid and cyst formulations of Azospirillum, combined with inorganic nitrogen, on the growth and yield of rice. Inoculation with the cyst formulation of Azospirillum enhanced the plant height, biomass and N uptake of the plants, the available nitrogen content of the soil and the yield of rice to the greatest extent when compared to carrier-based Azospirillum, followed by the liquid formulation. The results of the present study clearly indicated that the cyst and liquid formulations of Azospirillum could be used as bioinoculants more effectively than the carrier-based one.

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Changes in root morphology of wheat caused by Azospirillum inoculation

Cited by 142 publications

References 19 publications

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Expression of the Agrobacterium tumefaciens chvB virulence region in Azospirillum spp

Effect of liquid and cyst formulations of Azospirillum with inorganic nitrogen on the growth and yield of rice

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