PPI 2003 Meeting

Pickling Cucumber Improvement Committee Meeting

Wednesday, October 22, 2003

PPI Pickle Fair Trade Show, New Orleans, LA

Program

1:30 pm - Welcome; James Adkins, Chairman, 2003 PCIC
1:40 pm - Challenges and Success in Mechanically Harvested Pickling Cucumbers; Ed Kee and James Adkins, University of Delaware
2:00 pm - The Introgession of Cucumis hystrix Genes into Cucumis satiuvs; Jack E. Staub, USDA, ARS, University of Wisconsin-Madison; Jin-Feng Chen, Nanjing University, Nanjina, China
2:20 pm - The Genetics of Chilling Injury in Cucumber; Sang-Min Chung and Jack E. Staub, USDA, ARS, University of Wisconsin-Madison
2:40 pm - Engineering Cucumber Plants for Increased Tolerance to Salt Stress; Mohamed Tawfik and Rebecca Grumet, Michigan State University
3:00 pm - Investigation of Altered Plant Architecture as a Possible Means to Facilitate Phytophtora capsici Control in Pickling Cucumber; Kaori Ando and Rebecca Grumet, Michigan State University
3:20 pm - Break
3:35 pm - New NCSU Little-Leaf Pickling Cucumber Hybrids; Todd C. Wehner, Dept. of Horticulture, North Carolina State University
3:55 pm - Development of High Yielding Cucumbers; Todd C. Wehner, Dept. of Horticulture, North Carolina State University
4:15 pm - Survey of Plant Breeding Student Training at U.S. University; Todd C. Wehner, Dept. of Horticulture, North Carolina State University
4:35 pm - Development of an Improved Pickup Head and Conveyance Systems for Tractor- Mounted (Wilde/Raven) Harvesters; James Adkins and Ed Kee, University of Delaware
4:55 pm - Mechanical Harvest Options: A Discussion of the Wilde, Pik Rite, FMC, Lenco and other Harvester Designs; James Adkins and Ed Kee, University of Delaware
5:15 pm - Business meeting
5:30 pm - Adjourn

Abstracts

Challenges and Success in Mechanically Harvested Pickling Cucumbers

Ed Kee and James Adkins
University of Delaware Research & Education Center

Pickling cucumbers are produced on 8,000 acres in Delaware and the Eastern Shore of Maryland. All of this acreage is irrigated and harvested mechanically, in an once-over destructive harvest system. The system can be divided into four components: (1) Cultivar selection, (2) efficient production practice management, (3) pest control, especially disease control, and (4) efficient harvest.

The industry, both at the grower and processor level, must utilize the best possible genetic material in the form of available cultivars. Yield, appearance, quality, disease resistance, and maturity are factors considered in variety selection. Since 1994, we have conducted eleven trials over seven different years, evaluating forty-seven named or numbered cultivars. Typically, but not always, a spring and fall trial are conducted within one year. Over this period, the standard cultivars ‘Vlaspik’ and ‘Lafayette’ have been included in each trial. Over all the trials, ‘Vlaspik’ has an average rank of 4.1 in the trials; Lafayette a rank of 4.5. In other words, in most trials, higher yielding varieties existed, along with lower yielding varieties. No other variety was entered in more than five trials.

Producers currently employ excellent production practices. Precision planters are used to obtain precise populations of singulated seed. All plantings are irrigated and cultivated. Many growers use mechanically driven cultivators to avoid ridging often associated with conventional cultivators. Excessive ridging hinders cucumber recovery by the picking reel/pinch roller harvesters. While current University recommendations suggest 100 pounds of nitrogen/acre is the correct amount, field conditions and histories combine to create a wide variation in vine length, occasionally resulting in lighter colored pickles.
Phytophthora is a serious fruit rot disease. Wet weather conditions and increasing pressure on the rotation interval on irrigated acreage have compounded this problem. Rhizoctonia and pythium are also important fruit rot diseases.

Mechanical harvest production and harvest systems best facilitate the recovery of larger fruit. Seventy percent of the graded tonnage is concentrated in the 3A and 3b sizes (1.5 – 2.0 inches in diameter). Ten percent of the crop is graded as a crook or nub and discarded. An additional ten percent is discarded as broken or damaged. In summary, the production and harvest systems currently utilized necessarily harvest the larger size cucumbers and twenty percent of the harvested crop is typically discarded.

Efforts to achieve real and economic improvements are dependent on the recognition that each component identified above interfaces with every other component. An integrated and comprehensive approach is critical for continued progress.

The Introgession of Cucumis hystrix genes into Cucumis sativus

Jack E. Staub, USDA, ARS, Horticulture Department, University of Wisconsin-Madison
Jin-Feng Chen, Horticulture Department, Nanjing University, Nanjing, China

An interspecific hybrid between Cucumis hystrix Chakr. (2n = 24) x C. sativus L. (2n = 14) was reproduced by means of embryo rescue (2n = 19), and then subsequently its chromosome number was doubled to produce an amphidiploid (2n = 38). The amphidiploid was backcrossed and then self-pollinated to cucumber (Chinese type) to produce genetically enhanced cucumber germplasm. These backcross progeny (BC1S3) were fully fertile with C. sativus. Multiple harvest yield potential and length:diameter fruit ratio (i.e.,L:D, fruit quality component) of these BC1S3 progeny were evaluated in replicated trail at Hancock, WI in 2003. A test cross was made between a USDA inbred processing cucumber line (P-10) and a randomly selected BC1S3 individual. This hybrid was compared to the BC1S3 itself, line P-10 and 'Vlasset' for fruit yield and quality in four replications arranged in a randomized complete block design (~62,000 plants/ha). The monoecious BC1S3 progeny were relatively late flowering (~ 45 days) when compared to 'Vlasset' (~36 days), P-10 (~38 days), or the hybrid (~ 41 days). While 'Vlasset' and P-10 produced fruit approximately 42 days after sowing, the BC1S3 progeny and hybrid did not. Although yield of 'Vlasset' and P-10 was higher than either the BC1S3 progeny or the hybrid in the second harvest, the yield of both the BC1S3 progeny and the hybrid were higher than 'Vlasset' and P-10 in the fourth harvest. The mean cumulative L:D ratio of 'Vlasset', P-10, the BC1S3 progeny, and the hybrid fruit was approximately 3.0, 2.8, 3.9, and 3.4, respectively. The vegetative growth of both the progeny and the hybrid were remarkably light green in color and considerably greater than 'Vlasset' due to its highly branched growth habit (secondary and tertiary branches). These data and results from previous published communications suggest that amphidiploid-derived germplasm may be of value in the germplasm enhancement of cucumber.

The Genetics of Chilling Injury in Cucumber

Sang-Min Chung and Jack E. Staub, USDA, ARS
Horticulture Department, University of Wisconsin-Madison

Chilling temperatures (_12°C) can cause substantial economic damage to cucumber (Cucumis sativus L.) plants. Previous studies suggest chilling tolerance trait is controlled by nuclear gene(s). To investigate inheritance of chilling injury in cucumber, cucumber lines [susceptible GY14 (P1), tolerant 'Chipper' (P2), and tolerant 'Little John' (P3)], and their exact reciprocal F1 and F2 cross-progeny were evaluated to determine the inheritance of chilling injury at the first true-leaf stage when challenged at 4 °C for 5.5 hours. The mean chilling ratings [1(trace) to 9(dead)] of progeny comparisons were: F1(P1xP2) = 6.2 vs. F1(P2xP1) = 1.2; F2(P1xP2) = 6.4 vs. F2(P2xP1) = 2.7; F1(P1xP3) = 5.4 vs. F1(P3xP1) = 1.7; and F2(P1xP3) = 5.8 vs. F2(P3xP1) = 2.2. These data suggest that chilling tolerance was maternally inherited as is the chloroplast genome in cucumber. Parents, reciprocal F1, and F2 progeny were evaluated for variation using random amplified polymorphism DNA (RAPD). Although no maternally inherited RAPD markers were detected, polymorphic and paternally inherited RAPD bands AD21249, AV8916, and AV8969 amplified by AD2 and AV8 primers were cloned and sequenced. A "BLAST" search of these sequences suggested that their origin is likely cucumber mitochondrial DNA. These results indicate that the mitochondria genome is not associated with the chilling tolerant trait because this genome is paternally inherited in progeny derived from this reciprocal mating. Therefore, the results of maternally inherited chilling tolerant trait and paternally transmitted mitochondria genome support that the chilling tolerant trait as identified is likely associated with the chloroplast genome which is maternally transmitted in cucumber.

Engineering cucumber plants for increased tolerance to salt stress

Mohamed Tawfik and Rebecca Grumet
Horticulture Department, Michigan State University

Developing crops can be subject to environmental stresses such as drought and salinity that cause losses in yield and quality. In an attempt to increase stress tolerance of cucumber, we introduced the Arabidopsis thaliana CBF (C-repeat binding factor) gene. CBF encodes a transcription factor which has been shown to increase dehydration-stress tolerance in Arabidopsis and canola by inducing expression of stress responsive genes. CBF constructs were introduced into cucumber by Agrobacterium-mediated transformation of cucumber cotyledons. Gene incorporation and transfer to the following generations were verified using ELISA and PCR for six CBF1 and four CBF3 families. Segregation analyses indicate incorporation of a CBF at a single locus in each line. Gene expression was verified in T0 individuals and T2 families by RNA blot analysis. Results obtained from three greenhouse experiments demonstrated that transgenic CBF plants had elevated proline (5-7 fold) and sugar content (2-3 fold) relative to control (wild type and non-transgenic segregant) plants. The difference in proline and sugar levels between transgenic and non-transgenic plants was further increased in response to salt stress. Under non-salt conditions, growth of transgenic and non-transgenic plants was equivalent as measured by fresh weight, dry weight, and number of leaves. However, under salt stress conditions, transgenic families showed significantly less growth inhibition: 9-38% reduction at 100 mM NaCl (average 26% reduction) relative to 55-63% reduction for the non-transgenic plants. Accumulation of total soluble sugars and proline was correlated to the increased tolerance to salinity in transgenic plants as measured by accumulation of dry weight. A field experiment was performed during the summer of 2003 using two CBF1 and two CBF 3 lines in a split plot design with four replicates. As in the greenhouse, the transgenic plants had elevated proline (8-20 fold) and sugar content (2-5 fold) relative to the control plants under both non-stressed and salt stressed conditions. Under non-salt conditions, growth of the CBF and non-transgenic plants was equivalent as measured by vine growth (dry weight) and fruit yield. Under salt stress conditions (100 mM NaCl), the control plants showed a 51.8% reduction in dry weight, whereas transgenic plants showed only 0 - 27% reduction, with a mean reduction of only 7.4%. Salt stress also caused a 35% reduction in fruit number and 48% reduction in fruit weight for the non-transgenic plants. In contrast, on average, the CBF plants did not show reduction in either fruit weight or number: the average yield of transgenics was 6.9 kg/plot and 59 fruit/plot in the absence of salt and 6.9 kg/plot and 60 fruit/plot in the 100 mM NaCl plots. The two CBF3 lines showed modest decrease in yield (kg) (7-20%) while the two CBF1 lines showed a modest increase in yield (10-18%) in the salt stress conditions. These results in the greenhouse and field indicate that the transgenic CBF lines performed better under salt stress than did the non-transgenic control plants and suggest that the CBF gene may be useful in breeding for increased salt stress resistance in cucumber.

Investigation of altered plant architecture as a possible means to facilitate Phytophtora capsici control in pickling cucumber

Kaori Ando and Rebecca Grumet
Department of Horticulture, Michigan State University, East Lansing MI 48824

Phytophtora capsici is the most serious disease affecting pickling cucumber production in Michigan. Since P. capsici grows best in wet and warm conditions, modifying growth conditions to be less favorable for disease development may facilitate disease control. We sought to examine the possibility of reducing Phytophtora infection rates in pickling cucumber through the use of modified plant architecture. Our specific objectives were to: I. Test whether currently available differences in pickling cucumber plant architecture impact disease occurrence, and so might be potentially useful as a part of a control strategy for management of P. capsici, and II. Screen a collection of cucumber accessions identified to represent genetic diversity in the cucumber germplasm to test for additional variation in vegetative growth habit.

The Objective I experiments were performed on Phytophtora infested soil. Fruits were examined for disease occurrence at harvest, and again four days post harvest (dph). The first experiment tested the concept that altered canopy structure might mitigate Phytopthora occurrence by creating facsimiles of altered architecture using wide rows or trellises. The wide spacing plots in the spacing/trellis experiment showed reduced disease incidence in the first two harvests, but also had reduced yield relative to the narrow row spacing. Later in the season, when yields of the wide-spaced plots were comparable to the standard, narrow spacing, disease occurrence also increased to be comparable to that in narrow spaced plots (14 - 17% and 12 - 22%, respectively at 4 dph). The trellis plots, however, retained very low to no disease incidence throughout the season (0 - 4% at 4 dph), suggesting that removal of fruit from the contact with the soil could be helpful to reduce Phytophora infection. The second experiment tested the effect of altered plant architecture due to determinate, little leaf, or compact traits using several pickling cucumber genotypes. Each plot was paired with the control commercial cultivar, ‘Vlaspik’ to minimize effects of variation within the field. Percent diseased fruit at harvest ranged from 1.6% to 17.3% depending on genotype and location in the field. All genotypes showed high levels (47% - 82%) of visible disease at four days post harvest.

For the second objective, a set of 100 accessions was selected as a representative sample of the germplasm with maximum genetic variance based on studies by Knerr et al. (1989). An additional 50 were included based on annotation for possible short internodes or bush growth habit in the GRIN database. Variation was observed for traits such as stem and internode length, branching habit, and leaf size and shape. Among the variants observed were plants with determinate habit, reduced internode and vine length, variable leaf size, and reduced branching. In some plants, developing fruits were initially held above the ground, but as they grew larger, they came in contact with the soil. One type not among the pickling cucumber genotypes tested above, was reduced branching. Since it appears that reduced branching may result in a more open canopy, it will be of interest to further examine the non-branching accessions to test whether this trait may allow for reduced Phytophtora occurrence in the field. Fruit from all accessions also were also inoculated with P. capsici to test for direct resistance, which would be most desirable. Five showed possible resistance and will be examined further.

New NCSU Little-Leaf Pickling Cucumber Hybrids

Todd C. Wehner
Department of Horticultural Science, North Carolina State University

In 1980, a new plant type was discovered by Bowers and co-workers which became known as little-leaf (Ark. Farm Res. 29:4, 1980). The plant type was characterized by having little leaves, multiple branching, and multiple-fruiting ability. The plant type was later shown by Wehner and co-workers to be controlled by a single recessive gene for leaf size (Cucurbit Genet. Coop. Rpt. 10:33, 1987). A closely linked QTL (group of genes acting quantitatively) controls the multiple branching habit. The inbred line H-19 was released as a cultivar after selecting from the original line Ark. 75-79. The major advantage of the little-leaf type was not the small leaves or the multiple branching, but the simultaneous fruiting. Research by Schultheis, Wehner and Walters showed that little-leaf yields were significantly higher than for normal-leaf cucumbers, and fewer harvests were needed (Can. J. Plant Sci. 78:333, 1998). The two problems associated with the higher yield and more concentrated set were that the plants required two weeks longer to reach harvest stage, and the fruit were of lower quality, especially the larger grades. A series of little-leaf lines were developed at NC State University, and the best selections of each gynoecious and monoecious inbred were used to produce hybrids of the little-leaf type. The objective of this study is to evaluate the yield and fruit quality of little-leaf and normal-leaf cultivars, and to determine whether the greenstock and brinestock quality are acceptable to processors.

In general, fruit yields of little-leaf hybrids were higher, and percent culls were lower than for the check cultivars, which included 'Calypso' and 'Raleigh'. Harvest maturity was four days later for little-leaf than the normal-leaf types. That was early, since previous little-leaf cultivars have a two week later maturity. In general, the little-leaf hybrids were similar to the normal-leaf cultivars for vine size, vine color, disease resistance, sex expression, and fruit firmness. Performance of the little-leaf cultivars was excellent in the trials, with yield and earliness higher or the same as the check cultivars in all four environments (spring and summer of 2002 and 2003). Although the original Arkansas little-leaf was two weeks later than standard gynoecious hybrids, the maturity of the North Carolina little-leaf cultivars was only a few days later than the checks. The 2003 trials were run using 'Calypso' as the harvest indicator. If we had used the little-leaf cultivars as the indicator, the little-leaf cultivars would have performed much better in yield. Fruit quality of the little-leaf cultivars was similar to the checks in all trials and for all traits evaluated. No problems were noted for fruit shape, color, or seedcell. In the past, the Arkansas little-leaf has had problems with tough skin, watery seedcell, and large hard seeds in the greenstock and brinestock. No problems were observed with the North Carolina little-leaf cultivars for any of those traits in any of the trials.

Development of High Yielding Cucumbers

Todd C. Wehner
Department of Horticultural Science, North Carolina State University

This project is aimed at the rapid development of inbred lines having high yield. The objectives of this study were to identify high yielding pickling cucumber accessions, intercross the accessions to produce new combinations of the different yield genes, produce a high yielding base population, and produce high yielding inbreds from the population for use by industry, all by 2005. Methods involved seedling disease screening followed by cross- and self-pollination in the greenhouse to develop populations and inbred lines. The inbred lines were tested in the field for disease resistance, yield, earliness, and fruit quality using check cultivars for comparison. The highest yielding lines were tested for disease resistance in the greenhouse, and the best ones self pollinated to generate lines for testing in the field the following year. This year, 289 S1 lines and 15 check cultivars were tested in the field. Check cultivars were beaten in performance by 18 S1 lines that ranged in yield from 106 to 175% the yield of the checks. The 18 S1 lines were comparable to the checks in performance for earliness, percentage marketable fruit, fruit quality, and disease resistance (anthracnose and downy mildew). The selected lines were planted in the fall greenhouse for disease testing and self pollination of the best plants. In addition, the NC High Yield Pickle population was tested and intercrossed to produce half-sib families for testing next year.

Survey of Plant Breeding Student Training at U.S. Universities

Nihat Guner and Todd Wehner
Department of Horticultural Science, North Carolina State University

This survey was conducted to identify land grant universities in the U.S. with plant breeding programs, and to determine the number of domestic and international plant breeding students graduating at the M.S. and Ph.D. levels from those programs in 1995 to 2000. A total of 71 U.S. land grant universities were identified in the U.S. Of those, 51 offered graduate degrees in plant breeding. The survey had an 92% return rate. There were 409 (53%) Ph.D. and 361 (47%) M.S. degrees awarded. Of the total, 362 (47%) graduates were domestic and 408 (53%) were international. There was no major change in the total number of plant breeding graduates over the six-year period, indicating a constant demand by domestic and international students for training in that field of study. The largest numbers of plant breeding students were trained in agronomy (or crop science) departments, followed by plant breeding departments/groups, horticulture departments, plant science departments, and combined agronomy/horticulture departments. Based on the number of plant breeding students trained, the top seven universities involved in plant breeding training were University of Wisconsin-Madison, North Carolina State University, University of Nebraska-Lincoln, Cornell University, University of Minnesota-St. Paul, Iowa State University, and Texas A & M University. The downward trend noted in previous surveys has continued to the point where there are only a few universities with large plant breeding programs remaining in each region of the country. If the U.S. is going to continue its public effort in plant breeding research and graduate student training, sufficient federal and state funding will have to be provided to support at least the current regional centers.

Development of an Improved Pickup Head and Conveyance Systems for Tractor Mounted (Wilde/Raven) Harvesters

James Adkins and Ed Kee
University of Delaware

The recent development of a new pickle harvester designs with significantly higher recovery rates prompted the development of a new vine pickup header with improved recovery for use with the Wilde/Raven machines.

The rod chain over fingered chain pickup attachment was developed in 2002 for the Wilde/Raven tractor mounted pickle harvesters to simplify pickup head construction, maintenance, and to improve the recovery of pickles (Fig. 1). Testing of the 2002 design resulted in an average recovery improvement of 10% with the value of $60 per acre.

The goals for the 2003 design were to refine the header adjustments, allow for a wider range of header speeds, and to eliminate interference with the cross conveyor while implementing the concepts developed in 2002 (Fig 2).

The design consists of a rubber fingered rodded chain with rods spaced every 1.5 inches with staggered 2 in long rubber fingers, spaced 4 inches apart on every third rod. The fingered chain contacts the ground, picks up the entire severed cucumber plant and conveys the plants to the separation rolls. A similar fingerless rodded chain was mounted 3 in above the fingered chain to assist in pulling the vines into the machine. The 2 chains rotate at the same speed which may vary from 78-125 ft/min depending on the harvester’s forward travel speed.

The initial comparisons between the original cam operated pickup reel header and the new chain over fingered chain header showed an 11.7 bu increase in paid bushels per acre with the new system. Given the grade, yield and 2003 DE prices, the new design resulted in a $76 per acre increase in gross profits (Table 1).

The data collected demonstrates a significant improvement in crop recovery with the fingered chain pickup attachment over the traditional “Enos” type design. They show the potential for significant increases in grower profits through improved recovery, reduced maintenance costs, and larger throughput.

Mechanical Harvest Options: A Discussion of the Wilde, Pik Rite, FMC, Lenco and other Harvester Designs

James Adkins and Ed Kee
University of Delaware

The percentage of mechanically harvested pickle acreage in North America has increased from 40% to 60+% in the past 15 years. Much of the growth in the mechanically harvested acreage can be attributed to the scarcity of labor and the continual improvement of the harvesting machines. The increased demand and continued pressure for more efficient designs has led to the development of several different pickling cucumber harvester models.

Throughout the course of the University of Delaware Tractor Mounted Pickle Harvester Improvement project, we have gained significant insight into the operating and performance characteristics of many of the harvester designs. The objective of this presentation is to compile information about all the harvesting options and weigh the pros and cons of each harvester design. Many of the evaluations are based on first hand operating experience and observation from an agricultural engineer’s perspective, while some of the more obscure designs rely on grower performance claims.

As harvesting labor becomes harder to find, the role of mechanical pickle harvesters will continue to become even more important. Through the intense study of the design benefits of each harvester, better decisions can be made regarding the selection of the appropriate machine for any field conditions.