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Attractiveness of various upland rice genotypes to soil bacterivorous nematodes
Mahafaka Ranoarisoa, Eric Blanchart, Claude Plassard, Mathilde Sester, Kirsten Vom Brocke, Alain Ramanantsoanirina, Lilia Rabeharisoa, Jean Trap
To cite this version:
Mahafaka Ranoarisoa, Eric Blanchart, Claude Plassard, Mathilde Sester, Kirsten Vom Brocke, et al.. Attractiveness of various upland rice genotypes to soil bacterivorous nematodes. 5. International EcoSummit: Ecological Sustainability: Engineering Change, Aug 2016, Montpellier, France. 2016. �hal-02739496�
1 IRD, UMR 210 Eco&Sols, Laboratoire des Radio Isotopes (LRI), BP 3383, Route d’Andraisoro, Antananarivo 101, Madagascar, mahafaka-severine-patricia.ranoarisoa@ird.fr
2 INRA, UMR 1222 Eco&Sols, 2 Place Viala, 34060 Montpellier Cedex 2, France 3 UR AÏDA, CIRAD, DP SPAD, SRR Fofifa BP 230, Antsirabe 110, Madagascar 4 UR AGAP, CIRAD, DP SPAD, SRR Fofifa BP 230, Antsirabe 110, Madagascar 5 SRR Fofifa BP 230, Antsirabe 110, Madagascar
6 Laboratoire des Radio Isotopes (LRI), BP 3383, Route d’Andraisoro, Antananarivo 101, Madagascar
Patricia Mahafaka Ranoarisoa
1, Eric Blanchart
1, Claude Plassard
2, Mathilde Sester
3, Kirsten vom Brocke
4, Alain Ramanantsoanirina
5,
Lilia Rabeharisoa
6and Jean Trap
1Soil bacterivorous nematodes play a central role in terrestrial ecosystems. Their dispersion in the soil are favored by the existence of new bacterial-rich zones, such as in the plant rhizosphere. Benefits from bacterivorous nematodes on ecosystem functions, in particular on plant nutrition, derive from the ability of the cultivated plant to attract the nematodes close to their roots. This ability varies according to plant genotypes. In this study, we tested whether bacterivorous nematodes are attracted to the rhizosphere zone of eight upland rice genotypes growing in a poor-nutrient tropical soil in Madagascar.
M
ATERIALS
& M
ETHODS
Attractancy of nematodes to eight upland rice cultivars. The horizontal bars correspond to standard deviation (n=5). *p < 0.05; **p< 0.01 ; ***p < 0.001 according to a binomial test (5 replicates).
a
RESULTS
Nematode attractancy to different rice genotypes (positive, neutral or negative) varies according to the cultivars. In this study, bacterivorous nematodes were significantly attracted to the rhizosphere soil of F172, F152 and F182 but significantly repelled by the rhizosphere soil of WAB. From the PCA, the rice cultivars can be split into two groups:
Group (1): cultivars sensitive to NPK input, but showing poor growth in native soil and poor attractancy to nematodes. The nutrition of these
cultivars may not rely on the “soil microbial loop” but rather on mineral fertilizers. These cultivars are thus not suitable for agro-ecological
agriculture.
Group (2): cultivars showing poor sensitivity to NPK input, but able to grow in poor-nutrient native soil. These cultivars are able to attract the nematodes; and their nutrition may be based on the microbial loop. They are potential candidates for agro-ecological agriculture.
To conclude, our results suppose that developing new rice varieties with particular conventional breeding methods may alter the ability of cultivated plants to perform key functions such as nematodes attractancy.
b
Actives variables: Pds: seed weight (g) L: seed length (mm) W: seed width (mm)
Ratio: ratio between the length and the width of the seeds Seed-P: Phosphorus content in the seeds (mgP/kg MS)
Seed-N: Nitrogen content in the seeds (mgN/kg MS)
GR: germination rate of the seeds (%)
h32: height of the shoot after 32 days of growth (cm) SB: shoot biomass (g)
RB: root biomass (g)
BT: plant biomass (BT=SB+RB) (g)
SR: ratio between shoot and root biomass (SR= SB/RB) NPK: sensitivity to NPK input
The soil collected at Lazaina (Madagascar highlands) was sieved to 2 mm and then air-dried
1
Eight upland rice cultivars (Oryza sativa japonica) were selected:B22, Fofifa 182, Fofifa 172, Fofifa 152, Fofifa 154, Nerica 4,Chromrong Dhan and WAB 880
2
3
Tri-compartmental Petri dishes (90 mm diameter), with the first compartment opened to the other two, were used. Compartments 2 and 3 did not communicate. Around 100 bacterial-feeding nematodes (Cephalobidae sp.) were inoculated into the first compartment filled with agarose. Compartment 2 was filled with 10 g of rhizosphere soil. The last compartment was filled with 10 g of bulk soil. After 16 h at 25°C, the nematodes attracted to compartments 2 and 3 were counted.
4
For each rice cultivar, three seeds were planted in a pot containing 1kg of soil. Five replicates were set up for each rice cultivar.
5
After 32 days of growth, the soil adhering to the roots (rhizosphere) was sampled and air-dried
Attractancy test Agarose Bulk Rhizosphere Compartment 2 Compartment 3 Compartment 1 Inoculation of 100 nematodes
This work received support from the French state (Labex Agro: ANR-10-LabX-001-01), generated by the National Research Agency under the program "Future Investments".
Individuals: upland rice cultivars (B22, F182, F 172,
F 152, F 154, N4, CD and WAB)
Supplementary variables:
%Nem: percentage of nematodes that chose the rhizosphere
