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  • Author or Editor: John M. Labavitch x
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α-l-Arabinofuranosidases (α-Af) are plant enzymes that have the capacity to release terminal arabinofuranosyl residues from a wide variety of pectic and hemicellulosic polymers, as well as different glycoconjugates. Our interest in α-Af is related to its potential role in ripening-related loss of arabinose from tomato fruit cell walls. Using both control (cv. VF 36) and ACC synthase antisense (A11.1) tomatoes (Lycopersicon esculentum Mill.), we demonstrate that tomato α-Af activity is present during the entire ontogeny of the fruit. Immature 10-day-old fruit displayed 6-fold more α-Af activity on a per gram fresh weight basis, than mature green fruit. In VF 36 fruit, α-Af activity increased 45% from mature green 4 (48 days post anthesis) to light red stages (55 days) when fruit ripened on the vine. In contrast, no similar increase was detected in ACC synthase antisense fruit that do not ripen in the same time frame. However, when A11.1 fruit were detached at 48 days after anthesis and treated continuously with 100 mL·L-1 ethylene the fruit ripened and α-Af increased, as in ripening normal fruit. The α-Af activity pattern is similar to that reported for tomato β-galactosidases. The increasing α-Af activity during ripening and the decreased activity in antisense ACC synthase fruit after reaching the mature green stage suggest a role for ethylene in the ripening-related synthesis or activation of this enzyme.

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Third-generation navel orangeworm (Amyelois transitella) damage to almond (Prunus dulcis Mill.) kernels is a serious problem in the California almond industry. An early harvest is one means of reducing losses and increasing crop quality. A successful early harvest was accomplished 2 to 3 weeks before the normal harvest date, with no perceptible effect on kernel quality. Percent hullsplit was correlated with nut removal, providing a field guide to acceptable maturity. Within defined limits, yield, drying rate, and hullability of early harvested almonds were acceptable.

Open Access

The variation in polyunsaturated fatty acid content of walnut (Juglans regia L.) oils was determined by analysis of samples isolated from specimens growing in four germplasm collections [California (55 cultivars), Washington (64 seedlings), China (12 cultivars), and France (20 cultivars)]. In addition, the impact of within-state geographic differences on oil composition was examined by comparing samples from three California cultivars (`Ashley', `Hartley', and `Franquette') grown in three locations. Local environmental effects on oil composition of `Chico' were also examined by comparing 1) samples collected from shaded and sun-exposed locations of the same trees and 2) samples collected from trees subjected to three irrigation regimes. Polyunsaturated fatty acid content, as a percentage of total fatty acids, ranged from 47.2% in nuts from PI 142323 from France to 81.0% in `Ashley' from California. However, our data indicate that environment, genotype, nut maturity, and their interactions all contribute significantly to variation in the degree of unsaturation of walnut oil.

Free access