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  • Author or Editor: Barbara L. Goulart x
  • Journal of the American Society for Horticultural Science x
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Aluminum (Al) and phosphorus (P) interactions were investigated in mycorrhizal (M) and nonmycorrhizal (NM) highbush blueberry (Vaccinium corymbosum L.) plantlets in a factorial experiment. The toxic effects of Al on highbush blueberry were characterized by decreased shoot, root, and total plant dry mass. Many of the negative effects of Al on plant root, shoot, and total dry matter production were reversed by foliar P and N application, indicating P or N uptake were limited by high Al concentration. However, Al-mediated growth reduction in P-stressed plants indicated that the restriction of P uptake by high Al may not have been the only mechanism for Al toxicity in this experiment. Root Al and P concentration were negatively correlated in NM but not M plantlets, suggesting mycorrhizal infection may alter P uptake processes. Al uptake was also affected by mycorrhizal infection, with more Al accumulating in M plantlet roots and leaves. Correlations among foliar ion concentrations were also affected by mycorrhizal fungal infection.

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Strawberry, Fragaria × ananassa Duchesne ‘Redchief’, plants were grown in single plant-width rows on raised and flat beds at spacings of 13 cm, 50 cm, and 50 cm with runners set at 13 cm. Raised beds had more negative soil water potentials and more variable soil temperatures than flat beds. Plants on raised beds had deeper root distribution, poor runner-plant establishment, higher photosynthetically active radiation (PAR) penetration at one half canopy height in May, and earlier yield than those on flat beds. On raised beds, earliness of yield was enhanced by close spacing, and plants at the 13-cm spacing had more crowns per unit area than wide spacings. Total yield per unit area was not influenced by any treatment.

Open Access

The ability of mycorrhizal and nonmycorrhizal `Elliott' highbush blueberry (Vaccinium corymbosum L.) plants to acquire soil N under different preplant organic soil amendment regimes (forest litter, rotted sawdust, or no amendment) was investigated in a field experiment using 15N labeled (NH4)2SO4. Plants inoculated with an ericoid mycorrhizal isolate, Oidiodendron maius Dalpé (UAMH 9263), had lower leaf 15N enrichment and higher leaf N contents than noninoculated plants but similar leaf N concentrations, indicating mycorrhizal plants absorbed more nonlabeled soil N than nonmycorrhizal plants. Mycorrhizal plants produced more plant dry weight (DW) and larger canopy volumes. The effect of preplant organic amendments on the growth of highbush blueberry plants was clearly demonstrated. Plants grown in soil amended with forest litter produced higher DW than those in either the rotted sawdust amendment or no amendment. Plants grown in soils amended preplant with sawdust, the current commercial recommendation, were the smallest. Differences in the carbon to nitrogen ratio were likely responsible for growth differences among plants treated with different soil amendments.

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The effects of preharvest applications of pyrrolnitrin (a biologically derived fungicide) on postharvest longevity of `Bristol' black raspberry (Rubus occidentals L.) and `Heritage' red raspberry [R. idaeus L. var. strigosus (Michx.) Maxim] were evaluated at two storage temperatures. Preharvest fungicide treatments were 200 mg pyrrolnitrin/liter, a standard fungicide treatment (captan + benomyl or iprodione) or a distilled water control applied 1 day before first harvest. Black raspberries were stored at 18 or 0 ± lC in air or 20% CO2. Red raspberries were stored at the same temperatures in air only. Pyrrolnitrin-treated berries often had less gray mold (Botrytis cinerea Pers. ex Fr.) in storage than the control but more than berries treated with the standard fungicides. Storage in a modified atmosphere of 20% CO2 greatly improved postharvest quality of black raspberries at both storage temperatures by reducing gray mold development. The combination of standard fungicide or pyrrolnitrin, high CO2, and low temperature resulted in more than 2 weeks of storage with less than 5% disease on black raspberries; however, discoloration limited marketability after≈ 8 days under these conditions. Chemical names used: 3-chloro-4-(2'-nitro-3'-chlorophenyl) -pyrrole (pyrrolnitrin); N-trichloromethylthio-4-cyclohexene-l12-dicarboximide (captan); methyl 1-(butylcarbamoyl) -2-benzimidazolecarbamate) (benomyl); 3-(3,5 -dichlorophenyl) -N-(l-methylethyl -2,4-dioxo-l-imi-dazolidinecarboxamide (Rovral, iprodione).

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