| It was previously shown that Merlot fruit from the Oakville Experimental Station in Napa Valley grown on 1103P accumulated 1.7 times as much free amino acids (AA) as fruit from 101-14Mgt with no significant effect on tannin, iron-reactive phenolics, or anthocyanin. This work was expanded to include samples of Merlot (ME) and Cabernet Sauvignon (CS) from the Oakville Experimental Station (OK), Pinot noir (PN) from San Luis Obispo (SLO), Sauvignon blanc (SB) and Chardonnay (CH) from Monterey County (MO), as well as Syrah (SH), Chardonnay (CH), and ME from Washington State (WA). Offspring and parents of a hybrid Riesling (RE)xCS F1 population were also included. Berries sampled at commercial maturity were frozen, the skin was removed, and the seeds separated from mesocarp tissue. Berry components were ground in liquid nitrogen and extracted with 80% EtOH for AA analysis or 70% acetone for phenolic analysis. Rachis tissue from some samples was also included for AA analysis. Free AA and ammonium were determined by HPLC. Protein precipitated tannin and iron-reactive phenolics were measured using ferric chloride, and anthocyanins were assayed by pH change. This study confirmed the observation with ME at OK, and showed the rootstock effect on amino acid accumulation in the fruit to be reproducible between years. Samples of PN at SLO and SB at MO showed a similar effect, but CS at OK, SH at WA, and CH at WA showed the opposite effect, i.e. greater accumulation of nitrogen-containing species (NCS) in fruit from 101-14Mgt grafted vines. CH at MO showed no appreciable rootstock effect on NCS content. The effect of rootstock on NCS accumulation in the fruit appears to be variable and perhaps dependent on rootstock-soil interactions. Ripeness appeared to have an effect on NCS content, as samples of ME and CS with greater degree Brix had less disparity between skin and mesocarp concentration of NCS and rachis tissue from samples of CH, PN, and SB with lower oBrix had much higher NCS content. These two parameters may serve as useful diagnostic tools in determining the attenuation of nitrogen accumulation in grape berry. gamma-Aminobutyric acid (GABA) was determined to accumulate selectively in mesocarp relative to skin tissue of ripe berries, which may be due to relative stress of mesocarp tissue. Small but consistent increase in phenolic composition (expressed as per gram berry fresh weight) in fruit grown on 101-14Mgt across locations was observed. |
