Biswaray, A.

Germida, J.J.

Walley, F.

English

eCommons@USASK

The impact of inoculation on the tripartite association between pulse crops, rhizobia, and arbuscular mycorrhizal fungi

University of Saskatchewan Research Archive

The Impact of Inoculation on the Tripartite Association Between Pulse Crops, Rhizobia and Arbuscular Mycorrhizal Fungi   Anisha Biswaray  Department of Soil Science, University of Saskatchewan Saskatoon, SK Canada S7N 5A8    INTRODUCTION   • Arbuscular mycorrhizal fungi (AMF): obligate biotrophs, improved P uptake.  • Rhizobia: symbiotic N-fixing bacteria, form root nodules in legumes  Fig. 1.  A stained AMF colonized root  (http://aggie-horticulture.tamu.edu)  Fig. 2. Nodulated roots of pea(Dr. J. Burgess/Science Photo Library)    Rhizobia are known to improve the bioavailability of N, and this is may be enhanced in mycorrhized roots (Barea et al., 2002), and    Jia et al. (2004) concluded that plant productivity was enhanced by the the rhizobia/AMF/Vicia tripartitite relationship and some effects were either synergistic or additive, depending on the growth parameter assessed.   Legume mutant plants impaired in nodulation are also unable to associate with Glomeromycota (Lima et al., 2009)   Lipochitooligosaccharides(LCOs) activate a signaling pathway called the common symbiotic pathway (CSP), which controls both the rhizobium-legume (RL) and the arbuscular mycorrhizal (AM) symbioses and they are conserved (Kouchi et al., 2010)      PNAS 109:8316-8319  Both AMF and rhizobial associations involve the formation of specialized plant-based membranes, which surround the microbes and forms a “symbiotic interface” where the host plant and the microbes exchange nutrients in a controlled manner.   Ivanov et al. (2012) suggests that the signaling pathway for the formation of the membrane is similar between rhizobia-legume and AMF-legume, and that the former “co-opted”  the pathway from the more ancient arbuscular mycorrhizal symbiosis to form a symbiotic interface.   MtVAMP721d and MtVAMP721e are required for symbiosome and arbuscule formation.  Ivanov S et al. PNAS 2012;109:8316-8321 ©2012 by National Academy of Sciences  Legumes spend approximately 4-16% of their photosynthetic activity on each of the rhizobial and AMF symbioses (Kaschuk et al. 2010).   AMF associations vary from mutualistic to parasitic depending on AMF species, host crop and environmental conditions (Jones and Smith 2004; Schwartz et al. 2006).    Positive effects are only achieved if the benefits outweigh the costs of maintaining association (Kaschuk et al. 2010).      • Recent biotech advances have led to the introduction of AMF inoculants as ‘biofertilizers’.  • Pulse crops have typically high P requirement, alternative P management strategy.  • Additionally the possibility exists for the AMF inoculant to influence the rhizobial association because AMF and rhizobia share similar signaling pathways. OBJECTIVES  • To investigate the impact of AMF and rhizobial inoculation on the efficacy of the tripartite symbioses under field conditions.  • To assess the impact of the tripartite symbioses on the success of each participant in the symbiosis (i.e., AMF colonization, rhizobial nodulation and pulse crop growth parameters).   MATERIALS AND METHODS • Field trials with lentil (Lens culinaris cv. Clearfield Impress) and field pea (Pisum sativum L. cv.  CDC Meadow) were conducted in 2012 at Kelvington and Stewart Valley, SK.  • Sites were chosen on the basis of low levels of available P (4 kg ha-1 and 10 kg ha-1 to 30 cm, respectively).  • Completely randomized block design with four replicates. TREATMENT DESIGN Phosphorous Applied Rate of  MYKE® PRO GR  Rate of  Nodulator® Rate of JumpStart®  - - + - - 7.5 kg ha-1 + - - 15 kg ha-1 + - - - + + 16.8 kg ha-1  - + - 16.8 kg ha-1  7.5 kg ha-1 + - 16.8 kg ha-1  15 kg ha-1 + - 16.8 kg ha-1  - + + Figure 3(a). Field pea  at Kelvington 2 wks after emergence Figure 3(b). Field pea  at Kelvington at mid season. • Sampling : Midseason (early pod fill) and final harvest.   • Shoot biomass, nodulation and AMF colonization, seed yield and nutrient uptake.   • Biological nitrogen fixation is to be determined using the 15N natural abundance method.   • Results from the 2012 field season (field pea and lentils) from Kelvington and Stewart Valley are presented.   Fig 4(a). Mid-season biomass sampling at Kelvington. Fig 4(b). Mid-season root sampling at Kelvington. Figure 5. Impact of inoculation on midseason biomass of field pea at Kelvington. 0200400600800100012001400        0 P205         16.8 kg ha-1 P205      Total Biomass kg ha-1  2x AMF Control P only 2x AMF+ P Fig 6. Pea biomass response to fertilizer P and inoculation at midseason  at Kelvington Figure 7. Impact of inoculation on midseason biomass of lentils at Stewart Valley. 02004006008001000120014001600         0 P205         16.8 kg ha-1 P205       Total Biomass kg ha-1  Figure 8. Impact of inoculation on midseason P uptake of field pea at Kelvington. 00.20.40.60.811.21.4α=0.05 a ab bc bc bc c  c  c         0 P205         16.8 kg ha-1 P205      Total P uptake kg ha-1  Figure 9. Impact of inoculation on midseason P uptake of Lentils at Stewart Valley. 00.20.40.60.811.21.41.61.8        0 P205         16.8 kg ha-1 P205       a bc bc bc c c c α=0.05 ab Total P uptake kg ha-1    Figure 10. Impact of inoculation on midseason AMF colonization on field pea at Kelvington. 0102030405060708090         0 P205         16.8 kg ha-1 P205     AMF colonization %  Figure 11. Impact of inoculation on midseason nodulation on  field pea at Kelvington. 050100150200250ab ab ab ab b b b a         0 P205         16.8 kg ha-1 P205      α=0.05 Nodule Count Figure 11. Impact of inoculation on midseason nodulation on  Lentils at Stewart Valley. 050100150200250         0 P205         16.8 kg ha-1 P205       a b   c c c c c c α=0.05 Nodule Count DISCUSSION • P fertilizer enhanced mid season biomass at Kelvington and Stewart Valley.   • Magnitude of the biomass response to P was enhanced in the presence of both AMF and P. bilaiae.  • No additional benefit of doubling the AMF application rate. (New recommended rate is 5 kg ha-1)  • Similar results were obtained for P uptake.   • AMF colonization (%) was unaffected by any treatment, including AMF inoculants. In 2013 field trials, % root length colonized will be measured to take into account potential “dilution” in case of larger root biomass.   • Nodulation was highly variable; however, trends suggest that nodulation was unaffected by P fertilizer alone, but was enhanced when applied with AMF.   SUMMARY • Preliminary data suggest AMF inoculation may influence nodulation of both field pea and lentils.  • Doubling the application rate of AMF did not affect responses compared to the recommended rate.  • Biomass responses to AMF inoculation may reflect improved uptake of fertilizer P sources, in particular. NEXT STEPS • Sample processing is ongoing.  • Experiments will be repeated in 2013.  • Growth chamber experiments and in vitro experiments will be carried out to further study the mechanism controlling the interactions. ACKNOWLEDGMENTS  Drs. J.J. Germida and Fran Walley   Financial support by Saskatchewan Pulse Growers and the Natural Sciences and Engineering Research Council of Canada.    Financial support from the Harvey Graduate Scholarship   Help and support from fellow lab group members. THANK YOU !! 

https://harvest.usask.ca/bitstream/10388/8995/1/A.%20Biswaray%20et%20al.%2c%202013.pdf

The impact of inoculation on the tripartite association between pulse crops, rhizobia, and arbuscular mycorrhizal fungi

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