Nontreated seed, primed seed, and transplants were compared for effects on stand establishment, plant morphology, and yield of paprika pepper (Capsicum annuum L.). Nontreated seed was satisfactory for stand establishment, although primed seed had the potential to provide greater initial stands. When populations were made equal by thinning, there were few differences in stem and leaf dry weight, fruit yield, or plant morphology attributed to seed treatment. Generally, morphology of plants established by direct seeding was favorable for mechanical harvest. Using transplants did not result in higher marketable fruit yields than direct seeding in 2 of 3 years. When compared to plants established by direct seeding, three trends were consistent across all 3 years for plants established by transplanting: 1) they were more massive, 2) they had larger vertical fruiting planes, and 3) they had more branches. These traits increase the difficulty of mechanical harvest and create the potential for more leaves and stems (trash) in the harvested product. Thus, transplanting is not recommended for stand establishment of paprika pepper intended for mechanical harvest.
James R. Cooksey, Brian A. Kahn, and James E. Motes
James R. Baggett, Deborah Kean, and Kathryn Kasimor
Broccoli (Brassica oleracea L. Italica Group) lines with heads borne above the foliage (exserted) favorably for mechanical harvest were crossed with inbred lines with nonexserted heads. Length of the heads, defined as the portion of the plant above the highest major leaf, was ≈50% of the total plant height in short and tall parents and all plants of the F1, F2, and backcross generations. The principal characteristic identified with good head exsertion was long internodes. Internode length was inherited mostly in an additive manner, with some effect of hybrid vigor apparent in the F1, F2, and backcross to the tall parent. Plant height was also inherited in an additive manner. Head weight in the high-exsertion parent was much lower than in the low-exsertion parent. Within each parent and the F1, head weight was greater in plants with longer internodes and greater plant height. In the segregating generations (F2 and backcross), head weight increased with decreasing internode length, indicating that selection for high head exsertion would result in smaller heads and reduced yield.
Brian A. Kahn, James E. Motes, and Niels O. Maness
Mechanical harvest of paprika pepper (Capsicum annuum L.) produces a mixture of marketable and unmarketable fruit. Our objective was to increase the percentage of marketable red fruit in a once-over harvest by using ethephon to remove late-developing flower buds, blooms, and green fruit. Three experiments were conducted on field-grown plants in southwestern Oklahoma. We tested ethephon solutions of 0, 1000, 2000, 3000, and 4000 μL·L-1 as a one-time foliar application on various dates in September and October. Total dry mass of harvested fruit decreased linearly as ethephon rate increased in all experiments. Marketable fruit, as a percentage of total harvested fruit mass, increased linearly with ethephon rate in two of three experiments. Ethephon decreased the percent of total harvested fruit mass due to green fruit in all experiments. We recommend a single application of ethephon at about 2000 to 3000 μL·L-1 as a controlled abscission agent to increase the percentage of harvested red fruit in paprika pepper. The precise timing of the application will vary with the situation, but the last 10 days in September seemed an appropriate interval for southwestern Oklahoma. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
James W. Olmstead and Chad E. Finn
occurred; ‘Duke’, ‘Reveille’, and ‘Cara’s Choice’ were able to ripen and retain firmness on the bush. However, a concentrated ripening period was more desirable for mechanical harvest than extended holding ability, as an extended holding ability tended to
Ulrich Hartmond, Rongcai Yuan, Jacqueline K. Burns, Angela Grant, and Walter J. Kender
Methyl jasmonate (MJ) was tested as a potential abscission chemical to enhance mechanical harvest of `Hamlin' and `Valenica' orange [Citrus sinensis (L.) Osb.]. In field experiments, a solution of 1, 5, 10, 20, or 100 mm MJ was applied either as a stem wrap to individual fruit or as a spray to entire trees or canopy sectors. Solutions of 10, 20, and 100 mm MJ resulted in significant and consistent reduction of fruit detachment force and caused fruit drop within 7 to 10 days. Fruit loosening was preceded by an increase in the internal ethylene concentration of fruit similar to that of other experimental abscission compounds. While concentrations of 10 mm and less caused no or negligible phytotoxicity, solutions exceeding 10 mm MJ induced unacceptable levels of leaf abscission.
Mark K. Ehlenfeldt
in the north-temperate United States: reliable productivity, excellent yields, late-midseason ripening, medium-large fruit, uniform size, light-blue fruit color, and easy fruit removal force making it suitable for mechanical harvest. ‘Talisman’ is
Ramón A. Arancibia and Carl E. Motsenbocker
Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.
Yaying Wu, Brian A. Kahn, Niels O. Maness, John B. Solie, Richard W. Whitney, and Kenneth E. Conway
Research was conducted to develop a cultural system that would permit a destructive mechanical okra [Abelmoschus esculentus (L.) Moench] harvest. This paper reports on studies to determine the responses of okra plant architecture to various highly dense (HD) plant populations, and to consider the implications of those responses for destructive mechanical harvest. Growing okra in plant arrangements more densely planted than the control (which was spaced at 90 × 23 cm) did not affect overall plant heights. The position of the first bloom or fruit attachment and of the first marketable fruit attachment tended to become higher on the stem as plant population density increased, especially when comparing plants from the 15 × 15 cm spacing to control plants. The number of marketable fruit per plant was usually unaffected by plant population. Branch number and defruited dry weight per plant decreased as plant population density increased. Plant architecture did not affect the ability of an experimental mechanical harvester to recover marketable fruit from three different okra cultivars grown in a HD arrangement. The lack of concentrated marketable fruit set, rather than plant architecture, was the main limiting factor to the success of densely planted okra for destructive harvest.
R. Karina Gallardo, Eric T. Stafne, Lisa Wasko DeVetter, Qi Zhang, Charlie Li, Fumiomi Takeda, Jeffrey Williamson, Wei Qiang Yang, William O. Cline, Randy Beaudry, and Renee Allen
developing mechanical harvesting equipment that can substitute for the increasing shortage of hand labor is growing, especially for specialty crops such as blueberries. Research into mechanical harvesting of blueberries has been ongoing since the 1950s with
Marisa M. Wall, Stephanie Walker, Arthur D. Wall, Ed Hughs, and Richard Phillips
In the southwestern U.S. growing region, which includes southern New Mexico, west Texas, and southeastern Arizona, mechanical harvest of chile peppers (Capsicum annuum) is increasing because of the high cost of hand labor. Mechanical harvesters have been developed, but there is limited information on the performance of chile cultivars when machine harvested. Four red chile pepper cultivars (New Mexico 6-4, Sonora, B-18, and B-58) were grown in a farmer's field near Las Cruces, N.M., and harvested in October 2000 using a double-helix-type harvester. Ethephon was applied 3 weeks before harvest at 1.5 pt/acre (1.75 L·ha-1) to promote uniform ripening. Ethephon caused fruit of `B-18' and `B-58' to drop before harvest, thereby affecting yield results. Treatment with ethylene-releasing compounds is not recommended for these cultivars. `Sonora' and `New Mexico 6-4'dropped much less fruit than `B-18' and `B-58' after the ethephon treatment. Dry weight marketable yield ranged from 1419 to 2589 lb/acre (1590.5 to 2901.8 kg·ha-1), and total yield potential (discounting dropped fruit) ranged from about 2500 to 3100 lb/acre (2802.1 to 3474.6 kg·ha-1), depending on cultivar. Harvest efficiencies of 73% to 83% were observed among the cultivars. Trash content of the harvested chile varied from 25% to 42% of dry weight. Trash was predominantly diseased and off-color fruit, leaves, and small stems. Trash content was highest for `Sonora'. `New Mexico 6-4' had the greatest marketable yield and harvest efficiency among the cultivars evaluated in this study.