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Nitrification inhibition activity, a novel trait in root exudates of rice.

Pariasca Tanaka J, Nardi P, Wissuwa M - AoB Plants (2010)

Bottom Line: Soil incubation studies with concentrated root exudates of IAC25 showed significant reductions in NO(3) (-) formation.This effect was confirmed by detecting lower NO(3) (-) levels in incubation experiments using rhizosphere soil obtained from IAC25.Our results provide first evidence that root exudates of rice can reduce nitrification rates in soil.

View Article: PubMed Central - PubMed

Affiliation: Japan International Research Center for Agricultural Sciences (JIRCAS ) Crop Production and Environment Division, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686 , Japan.

ABSTRACT

Background and aims: Nitrification is an important process in soil--plant systems for providing plant-available nitrate (NO(3) (-)). However, NO(3) (-) is less stable in soils compared with ammonium (NH(4) (+)) and is more easily lost through leaching, runoff or denitrification. This study tested whether biological nitrification inhibition (BNI) activity is present in the root exudates of rice (Oryza sativa) and also the extent of variation between different genotypes.

Methodology: The BNI activity of root exudates was estimated by a bioluminescence assay using a recombinant Nitrosomonas europaea strain. Afterwards, the effect of a single application of concentrated root exudates and that of exudates deposited in the rhizosphere soil was tested on BNI using soil incubation. Soil was added with (NH(4))(2)SO(4) and water to reach 60 % of the water-holding capacity and incubated at 30 °C for different periods. Amounts of NH(4) (+) and NO(3) (-) were determined using a continuous-flow auto-analyser.

Principal results: In an initial screening experiment, BNI activity in the exudates of 36 different rice genotypes was evaluated using a bioassay based on a recombinant Nitrosomonas strain. Significant genotypic variation was detected with the upland cultivar IAC25 demonstrating consistently high BNI activity, while modern lowland varieties like Nipponbare or IR64 exhibited lower activity. Subsequent experiments ruled out the possibility that BNI activity is simply due to non-specific (solute) leakage from roots. Soil incubation studies with concentrated root exudates of IAC25 showed significant reductions in NO(3) (-) formation. This effect was confirmed by detecting lower NO(3) (-) levels in incubation experiments using rhizosphere soil obtained from IAC25.

Conclusions: Our results provide first evidence that root exudates of rice can reduce nitrification rates in soil. Having shown this for a model crop, rice, offers possibilities for further exploitation of this phenomenon through molecular and genetic tools.

No MeSH data available.


Related in: MedlinePlus

Nitrate accumulated in soil incubated for several hours with root exudates of two rice genotypes (Experiment 5). Soil was incubated following the nitrification potential method. Control refers to soil incubated without exudates. Different letters indicate significant differences within sampling times (LSD at P≤ 0.05).
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PLQ014F3: Nitrate accumulated in soil incubated for several hours with root exudates of two rice genotypes (Experiment 5). Soil was incubated following the nitrification potential method. Control refers to soil incubated without exudates. Different letters indicate significant differences within sampling times (LSD at P≤ 0.05).

Mentions: A subsequent experiment used a different ‘slurry’ incubation method to test BNI ability in root exudates of IAC25 and Nipponbare. After 6 h of incubation, 10.4 mg NO3− g−1 soil were detected in Lazio soil incubated with a water control (Fig. 3) compared with 8.3 and 6.9 mg NO3− g−1 in soil incubated with exudates from Nipponbare and IAC25, respectively. After 24 h of incubation, the NO3− concentrations had doubled to >20 mg NO3− g−1 soil in the water control but remained significantly lower for exudates of IAC25, confirming the potential of IAC25 for BNI using a completely different methodology.Fig. 3


Nitrification inhibition activity, a novel trait in root exudates of rice.

Pariasca Tanaka J, Nardi P, Wissuwa M - AoB Plants (2010)

Nitrate accumulated in soil incubated for several hours with root exudates of two rice genotypes (Experiment 5). Soil was incubated following the nitrification potential method. Control refers to soil incubated without exudates. Different letters indicate significant differences within sampling times (LSD at P≤ 0.05).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2992353&req=5

PLQ014F3: Nitrate accumulated in soil incubated for several hours with root exudates of two rice genotypes (Experiment 5). Soil was incubated following the nitrification potential method. Control refers to soil incubated without exudates. Different letters indicate significant differences within sampling times (LSD at P≤ 0.05).
Mentions: A subsequent experiment used a different ‘slurry’ incubation method to test BNI ability in root exudates of IAC25 and Nipponbare. After 6 h of incubation, 10.4 mg NO3− g−1 soil were detected in Lazio soil incubated with a water control (Fig. 3) compared with 8.3 and 6.9 mg NO3− g−1 in soil incubated with exudates from Nipponbare and IAC25, respectively. After 24 h of incubation, the NO3− concentrations had doubled to >20 mg NO3− g−1 soil in the water control but remained significantly lower for exudates of IAC25, confirming the potential of IAC25 for BNI using a completely different methodology.Fig. 3

Bottom Line: Soil incubation studies with concentrated root exudates of IAC25 showed significant reductions in NO(3) (-) formation.This effect was confirmed by detecting lower NO(3) (-) levels in incubation experiments using rhizosphere soil obtained from IAC25.Our results provide first evidence that root exudates of rice can reduce nitrification rates in soil.

View Article: PubMed Central - PubMed

Affiliation: Japan International Research Center for Agricultural Sciences (JIRCAS ) Crop Production and Environment Division, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686 , Japan.

ABSTRACT

Background and aims: Nitrification is an important process in soil--plant systems for providing plant-available nitrate (NO(3) (-)). However, NO(3) (-) is less stable in soils compared with ammonium (NH(4) (+)) and is more easily lost through leaching, runoff or denitrification. This study tested whether biological nitrification inhibition (BNI) activity is present in the root exudates of rice (Oryza sativa) and also the extent of variation between different genotypes.

Methodology: The BNI activity of root exudates was estimated by a bioluminescence assay using a recombinant Nitrosomonas europaea strain. Afterwards, the effect of a single application of concentrated root exudates and that of exudates deposited in the rhizosphere soil was tested on BNI using soil incubation. Soil was added with (NH(4))(2)SO(4) and water to reach 60 % of the water-holding capacity and incubated at 30 °C for different periods. Amounts of NH(4) (+) and NO(3) (-) were determined using a continuous-flow auto-analyser.

Principal results: In an initial screening experiment, BNI activity in the exudates of 36 different rice genotypes was evaluated using a bioassay based on a recombinant Nitrosomonas strain. Significant genotypic variation was detected with the upland cultivar IAC25 demonstrating consistently high BNI activity, while modern lowland varieties like Nipponbare or IR64 exhibited lower activity. Subsequent experiments ruled out the possibility that BNI activity is simply due to non-specific (solute) leakage from roots. Soil incubation studies with concentrated root exudates of IAC25 showed significant reductions in NO(3) (-) formation. This effect was confirmed by detecting lower NO(3) (-) levels in incubation experiments using rhizosphere soil obtained from IAC25.

Conclusions: Our results provide first evidence that root exudates of rice can reduce nitrification rates in soil. Having shown this for a model crop, rice, offers possibilities for further exploitation of this phenomenon through molecular and genetic tools.

No MeSH data available.


Related in: MedlinePlus