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`Lovell' peach seeds were stratified for 0 to 13 weeks at 4C under moist conditions. Heat of metabolism and CO2 evolution, measured by Differential Scanning Calorimetry, increased with stratification time. The calorespirometric ratio increased between 0 and 6 weeks and then remained constant until 13 weeks. Germination percentages paralleled this ratio and reached 80% only after 6 weeks of stratification.

After radicle emergence, seedlings from different stratification treatments were grown for 3 weeks. Increasing stratification time resulted in taller seedling growth. Calorimetrically measured CO2, evolution and the calorespirometric ratio of the apex (one cm) of the seedling increased with longer stratification time. Contrary to the observations of the seeds, metabolic heat rates decreased as stratification time increased. Yet, seedling sustained higher growth rates. These data suggest that the stratification treatment resulted in an improvement in metabolic efficiency.

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Weight loss and dehydration arc major problems limiting shelf life of early-season seedless grapes grown in the Sonoran Desert. This research was conducted to assess conditions improving cluster performance in cold storage (4C±1,. 90% R.H.). Clusters were packed: 1) loose, 2) wrapped in perforated plastic bags, 3) loose and water supplement added, and 4) in plastic bags + water supplement. After 12 days in storage, weight losses accounted for 7.0, 5.6, 8.5, and 4.0% of initial fresh weight for treatments in ascending order. In another experiment, individual clusters were stored in modified atmospheres using a high gas-permeability film with two different gas-exchange areas of 25 and 75 mm2. Cluster weight and gas composition significantly interacted with storage period. During the first 30 days, weight loss was not higher than 0.5% on every sampling date. Gas composition was affected by the effective exchange area After 47 days, CO2 concentration was 2.22% and 0.8% in the 25 and 75mm2 treatments. At any given time, oxygen content followed the opposite trend with final values of 18.9 and 20.0% for the same treatments. Although cluster quality was highly preserved, eventually rots developed.

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The effect of epiphytic bacteria population with different ice nucleation activity (INA) on the extent of supercooling of in vitro and leaf tissue disks of greenhouse-grown Capsicum annuum L. plants was determined. Bacterial strains were isolated on PDA and King's B medium from foliar samples of weeds from commercial apple orchards in Cuauhtemoc, Chihuahua, Mexico. Bacteria were screened by colony morphology, fluorescence under UV light, while growin on King's B medium plates and screened for ice-nucleating capability at -5 °C in suspensions of 108 cfu/mL. Ice nucleating (Ice+) and non-ice-nucleating (Ice-) active strains with fluorescent capacity were isolated from symptomless leaf samples. Four bacterial strains were used with different ina as epiphytic population models. Two Pseudomonas syringae strains, Pss29A and PD, from Oregon State Univ., with high Ice+ capability; P. fluorescens A-506, in its Blight Ban™ commercial lyophilized presentation; and UC001, a native fluorescent strain from CIAD-Cuauhtemoc; both Ice-strains. Freezing tests were carried out under controlled conditions. The high Ice+ strains Pss29A and PD increased the temperature of supercooling 2 and 1 °C compared to control samples. The non-inoculated tissue showed damage over 50% at -3 °C and below. Inoculated tissue with Ice+ strains (P. syringae 29A and PD), showed damage superior to 50% at -1 and -2 °C, respectively. Conversely, at none of the temperatures assayed, Ice-strains surpassed 50% damage. These results are of interest for further development of passive strategies towards minimizing damage due to low-temperature exposure of tropical vegetable crops.

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Apple embryos from moist seeds kept at 4 °C were used for a calorimetric characterization of Red and Golden Delicious apple seed dormancy. Seeds were sampled at 100-h intervals during 1200 h. The metabolic response of such samples was compared to that from chilled Golden Delicious seeds (>1200 h) stored under controlled atmosphere (CA). Isothermal calorimetry at 25 °C, evaluated metabolic activity (q), respiration rate (RCO2), metabolic 65 °C estimated activation energy (Ea) in a 10 to 20 °C range, and respiration coefficients (Q10) from 10 to 50 °C at 10 °C intervals. Data showed a direct relationship between chilling exposure and embryo metabolic responses from both cultivars. Once chilling requirement was satisfied, Red and Golden Delicious seeds presented a significant increase (P ≤ 0.05) in q, 0.94 and 0.98 μW/mg dry weight (dw); RCO2, 9.9 and 7.6 mmol CO2/mg dw; and RSG·ΔHB, 3.6 and 2.5 μW/mg dw, respectively. On the other hand, q/RCO2 did not follow a definite pattern, neither in Red nor Golden Delicious cultivars. Ea decreased 19.2 and 23.4 J/mol per °K per mg dw in Red and Golden Delicious, respectively, as a function of seed chilling. Q10 showed a significant response to temperature, but not to chilling exposure. Golden Delcious seeds from CA showed a significant reduction on q, RCO2, and RSG·ΔHB of 0.28 μW/mg dw, 2.47 mmol CO2/mg dw, and 14 μW/mg dw, respectively. Results show that calorimetry is a sufficiently sensitive, fast, and precise tool to quantify metabolic responses during seed chilling, as evolving energy.

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Table grapes grown in the Sonoran Desert of Mexico are mostly an export commodity directed to early season markets. In order to define the effect on canopy management on light use and berry ripening, `Perlette' vines planted along eastwest rows (typical in such a region) were trained under four systems: slanted pergolas (SP), CIAD, lyre (LY), and T-trellis with open canopies (TTOC). They were compared with traditional closed-canopy T-trellis (TT). Variables evaluated were photosynthetic active radiation (PAR), photosynthesis (PH), stomatal resistance (SR), chlorophyll content (CC), and berry total soluble solids (TSS). At harvest, PAR values for LY, SP, CIAD, TTOD, and TT were 2192, 2076, 1900, 885, and 771 μmol·m-2·s-1, respectively. In the same order, PH at veraison was 12.5, 12.7, 11.0, 10.5, and 5.1 μmol CO2/m2 per s, while in recently harvest vines it decreased to 9, 9, 8.1, 5.1, and 3.7 μmol CO2/m2 per s. SR at veraison was 3.4, 2.6, 2.8, 3.9, and 4.2 s/cm, but, after harvest it was 2.5, 3.5, 2.3, .2.9, and 6.8 s/cm. No significant differences in CC were found among treatments. TSS on 27 Apr. reached 14.9, 15.3, 15.7, 14.5, and 12.2 °Brix; on 29 Apr. they increased to 15.9, 15.5, 16.3, 15.1, and 13.1 °Brix. Based on the above, we demonstrated that canopy management and sunlight cropping represent a useful tool to advance table grape ripening, thus allowing an early harvest and therefore access to the high prices typical of early season markets.

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A microcomputer-based image processing system was used to simplify the large number of visual comparisons required to identify various Corylus spp., cultivars, and clonal accessions using polyacrylamide gel electrophoresis isozyme patterns. Photographs of gels stained for peroxidase, acid phosphatase, and phenol oxidase were digitally captured and selected lanes were enhanced and scanned. The scan data were analyzed to locate bands and normalize their position to that of standards. Such data were plotted and a computer-generated isozyme pattern was displayed. Compressed image data were then stored in a database for subsequent automated isozyme pattern comparisons. Photographic records that were previously used in published reports were reevaluated with the computerized system. Species, cultivars, or clones that were characterized in visual evaluations were similarly characterized using the computer method. Computer evaluations usually identified more bands. Band positions were only rarely different and probably resulted from better normalization relative to standard bands when using the computerized procedure.

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México is an important mango producer. During its marketing is necessary to maintain fruit quality for long periods to access distant markets. Modified (MA) and controlled (CA) atmospheres are used in some tropical fruits to attain these goals. In this work, we evaluated Keitt mangoes quality under CA (low O2 ≤0.3%) and MA with three low density polyethylene (LDP) films (100, 200 and 300 mils) during six days. CA fruit treated and LDP packed were stored for 30 days at 10C. Every three days, samples from CA and MA were evaluated, and every ten days a lot of treated fruits were transferred to 20C to determine fruit quality changes. We found that both, CA and MA (using LDP) delayed weight and firmness losses. Fruits kept a good appearance with a significative delay of the maturity process. However, fruit packed with 200 and 300 mils LDP developed a fermented taste after 10 days at 10C. Our conclusions suggest that these treatments prolong marketing and storage life of “Keitt” mangoes.

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Dehydration limits bell pepper postharvest life. Research had focused on waxes and individual sealed packages used to prolong shelf-life. Even though, the fruit natural package -the cuticle- is unknown; besides, cuticle functions as a barrier to protect fruits against excessive water loss. The objective of this work was to characterize cuticle changes and their relationships with fruit quality during postharvest handling. Green `Wonder' bell peppers were stored under marketing conditions (20C; 65-70% RH). Following cuticle isolation determinations included weight changes (CW), permeability and soluble cuticular lipids (SCL). In addition, quality characteristics like firmness, total soluble solids (TSS), titratable acidity (TA) and CO2 production were monitored every other day. CW and SCL decreased from 2798 to 1398 and 145 to 48 μg/cm2, respectively. Permeability was also reduced from 11 to 10 mg/cm2*h. CO2 climateric was reached between the 9 and 12th day peaking with 25 mg/kg*h. Firmness decreased from 2.1 to 1.1 Kg*f, while no noticeable changes were observed on TSS and TA.

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Crop uniformity is critical in early season table grapes, because it diminishes labor and improves chances to attain high prices. Single cyanamide applications are regularly used; however, harvest still requires several pickings. On 6 Dec. hydrogen cyanamide was applied to 4 year-old `Perlette' vines right after pruning or at different timings to advance and uniform harvest. Three rates (4, 6, and 8% Dormex) were applied as single or splitted applications. The later were made after 6, 12, 18, 24, and 48 hrs following the initial spray. The respective half rates were used in splitted applications. Our results showed that budbreak response to a single dose was 39, 71 and 93% for increasing dosages, nonetheless, buds broke unevenly. Divided rates improved both total budbreak and uniform development. However, timing between sprays also influenced the above characteristics. The best timing between applications was 6 hrs improving budbreak to 70, 75, and 100% for increasing concentrations. Since mostly primary buds broke, this also resulted in increased clusters per vine. Budbreak rates were significantly reduced when the second application was delayed by 48 hrs (30, 33, and 63% in the same order).

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An ampelographic collection was introduced to Comarca Lagunera, México in 1968. This work presents seven-year data of phenological evaluations on Cardinal, Queen, and Ribier mature vines, which are representatives of early, mid-, and late harvest seasons, respectively. Variables evaluated were the intervals required for a) budbreak (start to end), b) final budbreak to 50% bloom, c) 50% bloom to 50% vérasion, d) budbreak to vérasion, and e) soluble solids accumulation (SSA) after vérasion during the last two seasons. No significant differences were found for a), with averages around 213 Heat Units (HU, base temperature 10C). No differences were found either for b), with means close to 212 HU. However, differences (p≤0.001) were found for the interval bloom to vérasion with HU values for Cardinal, 720±32; Queen, 989±63; and Ribier, 1012±43. This interval accounted for the differences found in the whole cycle budbreak-vérasion. In the two-year study on SSA no differences in rates were found within genotypes, but among them. Therefore, our results suggest that -mainlythe bloom-vérasion period is responsible for defining the harvest season, along with budbreak timing and ripening rate.

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