The nutrient uptake and distribution patterns for N, P, K, Ca, and Mg were determined in mature (23 to 24 year old), field-grown, rainfed grapevines (Vitis vinifera L. `Pinot noir') growing in a red hill soil in Oregon in 2001 and 2002. Biomass, nutrient concentrations, and nutrient contents of all plant organs, including roots, were determined on 14 sampling dates over 2 years. There was no seasonal change in the standing biomass of primary roots (fine feeder roots), small woody (<4 mm diameter) or large woody (>4 mm diameter) roots. Trunk biomass also did not change during the 2 years, but all other vine organs showed significant seasonal changes in biomass. The rate of N uptake was greatest at bloom, when remobilization from reserves was also high. Nitrogen was also taken up after leaf fall in 2001, but not in 2002, when an early frost occurred before soil moisture recovery by fall rains. Uptake of N, K, and Ca from soil was similar between years, even though canopy demand for N and K was greater in 2002 (significantly larger crop). Phosphorus uptake from soil was lower in 2002 than in 2001, which was most likely due to the drier conditions in 2002. A greater quantity of canopy N, K, and especially P was supplied from stored reserves in the drier 2002 growing season. About 50% of canopy requirements for N and P were remobilized from reserves in the trunk and roots by the time of fruit maturity in 2002. Only 15% of canopy K and <5% of canopy Ca or Mg came from stored reserves in 2002. Our findings indicate that nonirrigated grapevines grown in Oregon acquire nutrients from soil earlier in the growing season and have a greater reliance on stored reserves of N and P than reported in previous studies from other growing regions. Replenishment of nutrient reserves occurred to large extent during the postharvest period. Rainfed vineyards in Oregon may require different nutrient management practices than irrigated vineyards, since low soil moisture may limit summer uptake of P.

No abstract

No abstract

The diversity of arbuscular mycorrhizal fungi (AMF) in 10 Oregon vineyards was assessed by examining spores in soil and amplifying mycorrhizal DNA from roots. Seventeen spore morphotypes were found in soil, including seven species in the Acaulosporaceae. Eighteen phylotypes were amplified from grape roots with AM1 and NS31 primers, and clones were dominated by Glomus spp. (> 99%). A few clones (< 1%) representing a single phylotype within Gigasporaceae, and a single clone within Archaeosporaceae were amplified from roots with AM1-NS31 primers. A separate experiment employing known proportions of grape roots colonized by Glomus intraradices or by Gigaspora rosea showed that fungi within Gigasporaceae might be underrepresented in clone abundance when Glomus spp. co-occur in roots. No clones representing fungi within the Acaulosporaceae were amplified from vineyards, although specific fungi within Acaulosporaceae were shown to colonize Pinot noir roots in sterilized soil and were amplified from these roots. Four Glomus phylotypes, including G. intraradices, were found in roots from all 10 vineyards, and these fungi accounted for 81% of clones. AMF phylotypes amplified from roots did not change during the growing season, although six phylotypes varied with soil type. The presence of three phylotypes was affected by vineyard age, and phylotype richness appeared to decline as vineyard age increased beyond 20 y. PCA analysis supported the hypothesis that the AMF community is different in red-hill soils than in valley soils and indicated certain phylotypes might be associated with lower soil and vine nutrient status. However, the changes in the AMF community in grape roots across vineyards were subtle because most root samples were dominated by the same three or four phylotypes. A separate analysis using primers to amplify AMF from the Archeasporaceae/Paraglomeraceae showed most root samples also were colonized by at least one Paraglomus or Archaeospora phylotype.

The spatial and temporal development of grapevine roots and associated mycorrhizal fungi was studied in 1999 and 2000 in a 21-year-old, Pinot Noir (Vitis vinifera L.) vineyard located on a Jory soil (Palehumult, silty clay loam) in Oregon, USA. The density of woody roots and fine (primary) roots deemed to be physiologically active (based on color and cellular integrity) were determined at monthly intervals in the weed-free, vine row and in the alleyway between rows at two depths (0-50 and 50-100 cm). The majority of fine roots were growing in the vine row at 0-50 cm depth. Fine root density did not change dramatically over the 1999 or 2000 seasons until the time of fruit harvest in the fall. Apparently, new root growth kept pace with turnover (death) prior to harvest, but new root growth surpassed turnover in the fall after fruit harvest. Colonization of fine roots by arbuscular mycorrhizal fungi (AMF) was consistently high in the vine row at 0-50 cm depth, but was lower in roots growing in the alleyway, and in roots below 50 cm. The proportion of fine roots containing arbuscules (the site of nutrient exchange in arbuscular mycorrhizas) was also greatest for roots growing in the vine row at 0-50 cm depth. Arbuscular colonization of these roots increased prior to budbreak in the spring, reached a high level (50-60% root length) by early summer, and remained high until after the time of leaf senescence in late fall. Arbuscular colonization decreased rapidly

No abstract

Intact, living roots of Brassica kaber (DC.) Wheeler and Brassica nigra. L. (Brassicaceae) were inhibitory to the germination of spores of the mycorrhizal fungi Glomus intraradices Schenck & Smith and Glomus etunicatum Becker & Gerd. Roots from two similarly non-mycotrophic species, spinach (Chenopodiaceae) and Amaranthus retroflexus L. (Amaranthaceae), had no effect on the germination of spores of G. intraradices. The roots of two out of three mycotrophic species examined were stimulatory to germination of G. intraradices. To test the hypothesis that the inhibition of VAM fungus spore germination by the roots of B. kaber and B. nigra was due to isothiocyanates (mustard oils), lysine, arginine and glutathione were added separately to the nutrient solutions applied to the plants. These compounds were expected to react with isothiocyanates released into the rhizosphere. In one experiment, lysine, arginine and glutathione restored the germination of G. intraradices to control levels for B. kaber, and nearly to the control levels for B. nigra. In a second experiment employing lower concentrations of lysine, arginine and glutathione, germination of spores of G. etunicatum in the presence of B. kaber roots was restored nearly to the levels of controls. In the same experiment, these treatments had no significant effects on spore germination in the presence of B. nigra roots. Lysine and arginine also protected spores of G. etunicatum from in vitro reactions of B. kaber root glucosinolate extract with myrosinase. The involvement of isothiocyanates in the resistance of mustards to VAM fungi is discussed.

Whole-canopy net CO 2 exchange (NCE C ) was measured near key stages of fruit development in grapevines (Vitis vinifera L. cv. Cabernet Sauvignon) that were managed under three approaches to regulated deficit irrigation (RDI): (1) standard practice (RDI S ), or weekly replacement of 60-70% of estimated evapotranspiration for well watered grapevines; (2) early additional deficit (RDI E ), or one-half of RDI S applied between fruit set and the onset of ripening (veraison), followed by RDI S ; and (3) RDI S followed by late additional deficit (RDI L ), or one-half of RDI S applied between veraison and harvest. Summed between fruit set and harvest, nearly 40% less irrigation was applied to RDI E vines and~20% less to RDI L vines than to those continuously under RDI S . After~5 weeks of additional deficit, NCE C in RDI E vines was 43-46% less per day than in RDI S vines. After RDI L vines had been under additional water deficit for~3 weeks, NCE C was 33% less per day than in RDI S vines. Instantaneous rates of NCE C responded rapidly to irrigation delivery and elapsed time between irrigation sets. Concurrent single-leaf measurements (NCE L ) reflected the relative differences in NCE C between irrigation treatments, and were linearly associated with NCE C (r 2 = 0.61). Despite halving the water applied under commercial RDI, mid-day stomatal conductance values in RDI E and RDI L of~50-125 mmol m -2 s -1 indicated that the additional deficit imposed only moderate water stress. There was no effect of additional deficit on yield or berry maturity.