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Abstract

Two surveys were conducted to evaluate the problem of low germination of carrot (Daucus carota L.) seed grown in the Columbia Basin area of Washington and Oregon. Analyses of weather data via a heat unit model demonstrated that the major difference in growing environment was the number of heat units (10C base) occurring before or during early bloom. The correlation between pre-bloom period heat units (May + June) and final percent germinability of seed lots from survey number one resulted in an r ² of 0.42 with the probability of F > 0.12. The second survey showed that the greatest reason for low seed germination among seed lots in 1984 was an increased percentage of abnormal germinants compared to 1983. This indicates that the seed germination problem in carrots may be due to seed being harvested at an immature stage, which resulted in low seed germination percentage.

Abstract

Root-knot nematode (Meloidogyne hapla) juvenile population increased and carrot (Daucus carota L.) yield progressively decreased during eight continuous carrot crops grown over 37 months. When ‘Haifa’ and common white clovers (Trifolium repens L.) were cropped for 29 months and plowed down, two succeeding carrot crops suffered severe yield and quality losses and the juvenile nematode population in the soil in-creased greatly. However, there were significantly fewer juveniles in the soil and significantly higher yield and better quality of carrots when nematode-resistant ‘Nevada Synthetic XX’ and ‘Nevada Synthetic YY alfalfas (Medicago sativa L.) and continuous cultivation preceeded the carrots.

The sensitivity of French prune (Prunus domestica L. syn. `Petite d'Agen') to water deprivation at various fruit growth stages was studied over 3 years in a drip-irrigated orchard. The soil was a poorly drained Rocklin fine sandy loam with a hardpan that varied from 4.75 to I m from the surface at the northern end of the orchard (shallow soil condition) to no hardpan apparent to 2 m below the surface at the southern end of the orchard (deep soil condition). Water deprivation during a) the first exponential phase of fruit growth or stage I, b) lag phase of fruit growth or stage II, c) first half of stage II, d) second half of stage II, e) second exponential fruit growth phase or stage III, and f) postharvest was compared to a fully watered control. Water deprivation caused the most severe reduction in tree water status when it was imposed over longer periods of time and during periods of high evaporative demand and also had mm-e severe effects under shallow soil conditions. Compared to the control treatment, deprivation during all of stage II (the most severe deprivation treatment) was associated with increased Ilowering, reduced fruit hydration ratio, and smaller fruit size under all soil conditions. Under deep soil conditions, deprivation during all of stage II resulted in increased return bloom, which was reflected in higher fruit loads and dry t-ha-' fruit yield. However, under shallow soil conditions, even though return bloom was increased with this treatment, fruit loads and dry t·ha^-1 fruit yields were the lowest of all treatments. These differences in treatment effects in shallow vs. deep soil conditions were most likely the result of increased fruit drop, which occurred under shallow soil conditions as a result of rapid onset and increased severity ofstress. Treatments that had parallel effects in shallow and deep soil conditions resulted in statistically significant overall treatment effects, while those that had opposing effects in shallow vs. deep soil conditions did not show significant overall treatment effects. Substantial alternate hearing occurred, and, in general, dry fruit yields above ≈9 dry t·ha^-1 resulted in a decrease in fruit load the following year, while loads below this value showed a subsequent increase. Based on a separate estimate of the theoretically stable value for each treatment, all deprivation treatments resulted in a higher sustainable fruit load compared to the fully irrigated control. This suggests that, for the purpose of prune fruit production, there may be an optimal level of tree water stress.

There are three main systems for the removal of carbon dioxide (CO₂) from controlled atmosphere (CA) stores: activated carbon (AC) scrubber, hydrated lime scrubber, and nitrogen (N₂) flushing. Each system is likely to have a different effect on the accumulation of volatiles other than CO₂ in the store atmosphere, and these volatiles may influence the storage performance of the produce. `Hayward' kiwifruit (Actinidia deliciosa) were stored at 0 °C (32.0 °F) under 2% oxygen (O<sub>2</sub>) and 5% CO<sub>2</sub> in CA rooms fitted with one of the three systems. In a fourth CA room, fruit were stored at 0 °C under air conditions. All four stores had their atmosphere scrubbed for ethylene. The store atmospheres and fruit firmness were monitored at intervals up to 27 or 14 weeks of storage in the 1999 or 2000 season, respectively. At the end of CA storage, and after an additional 4 weeks of air storage at 0 °C, fruit were evaluated for rots and physiological pitting. Linear discriminant analysis (LDA) showed the three CO<sub>2</sub> removal systems altered the volatile profiles of the store atmospheres differently. CA storage delayed fruit softening markedly, and once returned to air, softening resumed at a rate equivalent to that of fruit of equivalent firmness that had not been CA stored. There was little effect of CO<sub>2</sub> removal system on the fruit softening during storage. Although CA storage resulted in a higher incidence of rots, there was little difference among CO<sub>2</sub> removal systems compared to the main effect between air and CA storage. Similarly, CA storage delayed the appearance of physiological pitting, although the incidence increased rapidly during an additional 4 weeks of storage in air, and was higher than for fruit stored throughout in air. Among the CO<sub>2</sub> removal systems, N<sub>2</sub> flushing resulted in fruit with the lowest incidence of physiological pitting. It is concluded that different CO<sub>2</sub> removal systems alter room volatile profiles but may not consistently affect the quality of `Hayward' kiwifruit during CA storage.