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Title:   Author  item
                                            CHENG, XIAOMEI - UC DAVIS, PLANT PATHOLOGYitem
                                            Euliss, Amyitem
                                            Baumgartner, Kendra
  Submitted to: Biology and Fertility of Soils
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 2/4/2008
                                    Publication  Date: 8/1/2008
                                    Citation: Cheng, X., Euliss, A.L., Baumgartner, K. 2008. NITROGEN CAPTURE BY GRAPEVINE ROOTS AND ARBUSCULAR MYCORRHIZAL FUNGI FROM LEGUME COVER CROP RESIDUES UNDER LOW RATES OF MINERAL FERTILIZATION. Biology and Fertility of Soils. 44:965-973.Interpretive Summary: The influence of low levels of fertilization on arbuscular mycorrhizal fungi (AMF)-mediated nitrogen (N) capture from a legume crop (Medicago polymorpha) was examined in grapevines. We hypothesized that, because the mycorrhizal host was grown in nutrient-poor soil, that fertilization would increase both host and fungal growth and, in turn, increase 15N uptake by both roots and hyphae from the residue. Plants were grown in low fertility soil and were either fertilized or nonfertilized. Specially-designed cores surrounded by mesh were vertically inserted into containers to allow mycorrhizal roots and extraradical hyphae (mycorrhizosphere treatment), extraradical hyphae (hyphosphere treatment), or neither (bulk soil treatment) to proliferate residue inside the cores. Our findings of higher levels of N in the grapevines, higher grapevine biomass, and higher intraradical colonization of fertilized vines indicate that fertilization stimulated growth of both the host and the fungus. Fertilization did not affect extraradical colonization or root biomass of the hyphosphere and mycorrhizosphere cores, respectively, but did significantly lower 15N atom% excess and %N derived from the legume residue (%NDFL) in leaves and stems of fertilized vines by approximately 50%. Our results suggest that minimal fertilization may decrease grapevine N uptake by mycorrhizal roots and extraradical hyphae from legume cover crops.
                                Technical Abstract: The influence of minimal fertilization on arbuscular mycorrhizal fungi (AMF)-mediated 15N capture from a legume crop (Medicago polymorpha) was examined in Vitis vinifera. We hypothesized that, because the mycorrhizal host was grown in nutrient-limiting soil, minimal fertilization would increase both host and fungal growth and, in turn, increase 15N uptake by both roots and hyphae from the residue. Plants were grown in low fertility soil and were either fertilized with 0.25X Hoagland’s solution or nonfertilized. PVC cores surrounded by mesh were vertically inserted into containers to allow mycorrhizal roots and extraradical hyphae (mycorrhizosphere treatment), extraradical hyphae (hyphosphere treatment), or neither (bulk soil treatment) to proliferate residue inside the cores. Our findings of higher tissue N and biomass, and higher intraradical colonization of fertilized plants indicate that fertilization stimulated growth of both the host and the fungus. Fertilization did not affect extraradical colonization or root biomass of the hyphosphere and mycorrhizosphere cores, respectively, but did significantly lower 15N atom% excess and %N derived from the legume residue (%NDFL) in leaves and stems of fertilized plants by approximately 50%. Our results suggest that minimal fertilization may decrease grapevine N uptake by mycorrhizal roots and extraradical hyphae from legume cover crops.


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