Parthenocarpic Cucumber Cultivar Evaluation in High-tunnel Production (2024)

Southwest Purdue Agricultural Center.

The experiment was conducted in a gothic-style high tunnel (Rimol Greenhouse Systems, Hooksett, NH) that was 30 ft wide and 96 ft long, with 6-ft side walls and 15-ft centers. The high tunnel was equipped with a ridge vent, which opened when temperatures inside the high tunnel reached 75 °F and closed when temperatures dropped below 60 °F. The side walls were opened when temperatures inside high tunnel were more than 80 °F. Cucumber plants were transplanted in the high tunnel on 12 Apr. into raised beds with 4-ft center-to-center bed spacing. Beds were covered with black plastic mulch with one drip tape with 8-inch emitter spacing in the middle of each bed. The in-row plant spacing was 1 ft apart. Plants were fertigated three times per day beginning 2 weeks after transplanting with potassium nitrate (13.7N–0P–38.5K) (Krista K; Yara International, Oslo, Norway) and urea ammonium nitrate solution (28N–0P–0K) (CF Industries Holdings, Deerfield, IL) at a rate of 1 lb/acre nitrogen (N) per day in May, and 1.5 lb/acre N per day in June and July. A total of 128 lb/acre N was applied during the season. Water application rate ranged from 60 to 270 gal/d per high tunnel. Irrigation started at 20 gal of water for each irrigation event for the entire high tunnel in May; then, it was gradually increased to 90 gal of water for each irrigation event in July. Irrigation was paused on rainy days. Throughout the season, soil moisture was maintained around field capacity. A soil moisture sensor (5TE; Meter Group, Pullman, WA) was used to guide irrigation management. The average volumetric water content was ≈0.2 m³·m⁻³ at a soil depth of 10 inches.

Potassium salts of fatty acids (M-Pede; Dow AgroSciences, Indianapolis, IN) at a rate of 0.076 lb/gal a.i. were sprayed on 8, 16, and 24 May, and on 20 June for aphids (Aphididae) and two-spotted spider mite control. Bifenazate (Acramite 50WS; Chemtura Corp., Middlebury, CT) at a rate of 0.37 lb/acre a.i. was sprayed on 20 June for two-spotted spider mite control.

The cucumber plants were trellised to a single leader system. Side shoots were pruned weekly. Old foliage at the base of the plant was pruned biweekly, leaving ≈15 fully expanded newer leaves on each plant. The same pruning method was used at the three sites. Vines were then lowered to the ground. A randomized complete block design with four replications and four plants per cultivar per replication was used in the experiment.

Pinney Purdue Agricultural Center.

The experiment was conducted in a gothic-style high tunnel (Rimol Greenhouse Systems) that was 30 ft wide and 48 ft long, with 4-ft side walls and 14-ft centers. Side walls were thermostatically controlled and set to open when temperatures inside the high tunnel were above 80 °F and close to below 60 °F. End walls were left open after 6 June. Cucumber plants were transplanted in the high tunnel on 23 May into raised beds with 4-ft center-to-center bed spacing. The beds were covered with black plastic mulch with two lines of drip tape with 12-inch emitter spacing along each side of the plant row. Plants were 1 ft apart in the plot. Fertilizer was incorporated when beds were formed at a rate of 100 lb/acre N from 46N–0P–0K (Shaw’s Turf Food; Knox Fertilizer Co., Knox, IN) and 100 lb/acre K from 0N–0P–50K (Kova, Greensburg, IN). Plants were irrigated manually after transplanting. After establishment, plants were irrigated every day or every few days based on observations of soil moisture and weather conditions, with 50 to 150 gal/tunnel supplied per day. To assist with monitoring soil moisture, dielectric soil moisture sensors (10HS Soil Moisture Smart Sensor; Onset Computer Corp., Bourne MA) were installed at depths of 6 and 12 inches. Sensor readings logged every 10 minutes recorded an average daily minimum volumetric water content of 0.282 at the 6-inch depth and 0.305 at the 12-inch depth for the period from 16 June to 8 Aug.

Permethrin (Arctic 3.2EC; Winfield Solutions, St. Paul, MN) at a rate of 0.2 lb/acre a.i. and acequinocyl (Kanemite; Arysta LifeScience North America, Cary, NC) at a rate of 0.3 lb/acre a.i. were applied on 13 July for striped cucumber beetles (Acalymma vittatum) and squash bugs (Anasa tristis) control. A randomized complete block design was used during the experiment, with six replications and two plants per cultivar per replication.

Dixon Springs Agricultural Center.

Cucumber plants were grown in a 35- × 96-ft gothic-style tunnel (Zimmerman’s High Tunnels and Greenhouses, Versailles, MO) with fixed sidewall curtains and end walls. Air temperature in this tunnel was regulated by a thermostat set at 80 °F, and shutters and exhaust fans were opened and closed accordingly. Two horizontal airflow fans continually circulated air to help reduce humidity. A 30% shadecloth was installed on the tunnel on 1 June. The floor of this tunnel was limestone gravel.

Cucumber plants were transplanted into hydroponic greenhouse pots (Bato-bucket; Bato Plastics, Zevenbergen, the Netherlands) filled with perlite (Aero-Soil horticultural Perlite; Chem-Rock Co., Jacksonville, FL) on 23 Apr. Two plants were placed in one pot. The pots were placed 18 inches apart in rows that were 5-ft center-to-center. The fertigation schedule was based on plant water needs. One week after transplanting, each plant received 1 gal of water per day with 0.01 lb complete fertilizer (3N–6.5P–23.2K) (Ultrasol; SQM North America Corp., Atlanta, GA) and 0.005 lb calcium nitrate (15.5N–0P–0K) (YaraLiva Calcinit; Yara United States, Tampa, FL). The fertigation solution was maintained at 1.8 mS·cm⁻¹ EC and 6.5 pH. Plants were spaced at 3.75 ft² per plant. A total of 0.097 lb N per plant was delivered during the course of the trial.

Flonicamid (Beleaf 50SG; FMC Corp., Philadelphia, PA) was sprayed at a rate of 0.062 lb/acre a.i. on 1 June for aphid control; Bacillus thuringiensis (DiPel DF; Valent U.S.A. Corp., Walnut Creek, CA) was sprayed at a rate of 0.54 lb/acre a.i. on 8, 15, and 29 June, and on 13 and 20 July for caterpillar (Lepidoptera) control. Permethrin (Perm-Up 3.2 EC; United Phosphorus, King of Prussia, PA) was sprayed at a rate of 0.2 lb/acre a.i. on 18 May, 29 June, and 13 July for striped cucumber beetle control. A randomized complete block design with four replications and four plants per cultivar per replication was used during the experiment.

Cucumber yield.

Harvests lasted from 7 May to 30 July, 14 May to 30 July, and 13 June to 8 Aug. at SWPAC, DSAC, and PPAC, respectively. Harvest of Beit alpha and mini cucumbers started less than 30 d after transplanting. The American slicer cultivars were harvested 3 to 4 d later than Beit alpha and mini cucumbers. The harvest of Dutch greenhouse and Japanese cultivars started 1 to 2 weeks later than that of any of the other cultivars.

The total yields of cucumbers ranged from 14.0 to 23.3 lb/plant at SWPAC, 13.5 to 19.8 lb/plant at DSAC, and 7.4 to 16.3 lb/plant at PPAC (Table 2). Overall yields at PPAC were lower than those at SWPAC and DSAC. A shorter harvest period and the different fertility management may have contributed to the yield difference. At PPAC, fertilizers were applied preplant following the recommendations of field-grown cucumbers (Egel et al., 2018). Because of the extended harvest in high tunnels compared with field production, fruit abortion and yellowing of old leaves were observed on these cucumber plants, especially toward the end of the production season. Plant tissue analyses confirmed low nitrogen and deficient potassium levels in these plants (data not shown). At SWPAC and DSAC, plants were fertigated daily following the recommendations for greenhouse cucumber production (Papadopoulos, 1994). Nutrient deficiency symptoms were not detected at these locations.

At each location, the cultivar that produced the highest total yield was a Beit alpha or mini type; these were Picolino, Jawell, and Manny at SWPAC, DSAC, and PPAC, respectively (Table 2). Beit alpha cucumbers are known for high productivity (Cantliffe et al., 2004). Under optimal growing conditions, three to five fruit may be harvested at each node (Shaw et al., 2000).

At SWPAC, Beit alpha cucumbers, except for ‘Jawell’, had total yield similar to the highest-yielding cultivar Picolino. The total yields of Japanese cultivars Tasty Jade and Taurus and American slicer cultivars Sweet Success and Corinto were also similar to that of Picolino. At PPAC, Beit alpha cultivars Manny, Katrina, and Socrates had the highest total yields, and they were not significantly different from the ‘Corinto’ American slicer cucumber. At DSAC, total yields were not significantly different among all the Beit alpha and mini, Dutch greenhouse, and Japanese cultivars Tasty Jade and Taurus, but the yields of American slicer cucumbers, except Sweet Success, were lower. Consistently among the three sites, ‘Tasty Green’ Japanese cucumber had the lowest total yield among the evaluated cultivars.

Averaged among cultivars, unmarketable fruit accounted for ≈30% of the total yield at SWPAC and PPAC (Table 3). Unmarketable fruit could be further divided as misshaped and scarred fruit. Fruit that were categorized as misshaped were either severely curved or tapered (U.S. Department of Agriculture, 1985). ‘Sweet Success’ had a high percentage of misshaped fruit, especially at SWPAC, which accounted for 36.9% of the total yield. The majority of the misshaped fruit had tapering at the blossom end. The three Dutch greenhouse cultivars had an average of 25.7% and 15.8% misshaped fruit at SWPAC and PPAC, respectively. Japanese cultivars Tasty Jade and Tasty Green also had higher percentages of misshaped fruit that accounted for 16.2% and 14.3% of the total yields at SWPAC and PPAC, respectively. Those misshaped fruit mainly had curving.

American slicers ‘Corinto’, ‘Lisboa’, and ‘Alcazar’ and the Beit alpha cultivars had lower percentages of misshaped fruit. However, a large percentage of Beit alpha cucumbers had scarred fruit because of either insect feeding damage or mechanical injury. Among the evaluated cultivars, Corinto had the highest fruit marketability; Lisboa and Alcazar also had high fruit marketability at both SWPAC and PPAC.

Unmarketable fruit comprised less than 15% at DSAC (data not shown), where cucumbers were grown in a structure that was equipped with fixed sidewall curtains and end walls, and temperatures were controlled through opening and closing shutters and exhaust fans. In contrast, at PPAC and SWPAC, side and end walls of the high tunnels remained open most of the time when temperatures were above 80 °F, and plants were exposed to wind. Fruit became scarred by rubbing on plant parts, strings, or clips. The open environment also allowed the entry of insect pests such as cucumber beetles (A. vittatum and Diabrotica undecimpunctata), squash bugs, and yellow striped armyworms (Spodoptera ornithogalli), which caused aesthetic damage to fruit skins. The open environment also facilitated pollination. It is known that parthenocarpic cucumbers may develop misshaped fruit when female flowers are pollinated (Papadopoulos, 1994). However, these undesirable effects due to the open high-tunnel environment were seldom observed on American slicer cultivars. This was particularly noticed for ‘Corinto’, which had the highest marketable yield at PPAC and one of the highest marketable yields at SWPAC.

Interestingly, the average total yield of Beit alpha and mini cucumbers was 7.6 lb/plant lower at PPAC than at SWPAC, whereas the yield difference between the two sites was 3 lb/plant for American slicer cucumbers (cultivars Corinto, Lisboa, and Alcazar). A similar trend was also observed when comparing the yields of Beit alpha cucumbers and American slicer cucumbers at DSAC and PPAC (Table 2). The relatively better performance of ‘Corinto’, ‘Lisboa’, and ‘Alcazar’ compared with Beit alpha and mini cucumbers at PPAC may suggest that American slicer cucumbers are better adapted to production systems that do not rely on intensive fertigation compared with Beit alpha and mini cucumbers.

The marketable fruit number varied greatly among cultivars and cucumber types (Table 2). Generally, cultivars with smaller cucumbers produced greater numbers, and cultivars with larger cucumbers produced fewer. For example, cultivar Picolino, harvested at the shortest length, consistently produced the most fruit per plant. In contrast, Dutch greenhouse-type cucumbers, Japanese cucumbers, and ‘Sweet Success’, all harvested at longer lengths, produced the least number of fruit.

Plant vegetative growth.

The growth rate of cucumber main stems and the growth of side shoots are of great importance to growers because they influence the amount of labor needed for trellising and pruning the cucumber plants in a single-stem vertical growing system. Among the evaluated cultivars, Tasty Green produced the most side shoot growth. Fresh weight of these shoots was significantly greater than that of other cultivars, except Taurus (Table 4). ‘Lisboa’ developed the least side shoot growth and was not significantly different from ‘Jawell’, ‘Corinto’, ‘Katrina’, ‘Sweet Success’, ‘Tyria’, and ‘Manny’. Consistent among the three locations, ‘Corinto’ was one of the cultivars that had the greatest length of main stems 1 month after transplanting. The main stems of ‘Tasty Green’ and ‘Alcazar’ also grew faster than those of the majority of the other cultivars.

Plant sexual type.

Location of the first female flower is important because it influences early yield. For long cucumbers, it also provides an indication of whether the first flower should be allowed to produce fruit; if the node is too close to the ground, then the cucumber may touch the ground, curve, and become unmarketable. Dutch greenhouse, Beit alpha and mini, and the American slicer cultivars that were selected for the evaluation are gynoecious plants that produce only female flowers. The first female flower developed on the second or third node of American slicer and Beit alpha and mini types, and on the third to fifth node of Dutch greenhouse types (Table 5). Female flowers then produced on each subsequent node on the main stem of the plant. Japanese cultivars are monoecious plants that bear both male and female flowers. The plants produce male flowers initially. The first female flowers were initiated on the fourth to sixth node on the main stem.

Monoecious cultivars have not been recommended for greenhouse cucumber production because they require more pruning, take longer to produce fruit, and have lower yields (Papadopoulos, 1994). Furthermore, the monoecious cultivar Tasty Green had a lower yield and greater vegetative growth. However monoecious cultivars Tasty Jade and Taurus showed promising yield potential. The development of side shoots by ‘Tasty Jade’ was comparable to that of most gynoecious-type cultivars.

Comparative resistance to powdery mildew and two-spotted spider mites.

Plant resistance to powdery mildew varied greatly among cultivars at SWPAC. The Japanese cultivar Tasty Jade had significantly more powdery mildew than all other cultivars (Table 6). ‘Taurus’ was also moderately susceptible to powdery mildew. Among the Dutch greenhouse cultivars, ‘Kalunga’ was significantly more susceptible to the disease, whereas ‘Tyria’ was the least susceptible cultivar. In the group of Beit alpha and mini cucumbers, ‘Jawell’ had significantly more disease than the other cultivars, although the disease severity was significantly lower than that of ‘Tasty Jade’, ‘Taurus’, ‘Kalunga’, and ‘Camaro’. All the American slicer cultivars evaluated during this trial were fairly resistant to this disease. A similar trend was observed at DSAC (data not shown).

Cucumber resistance to powdery mildew is controlled by multiple genes, and this resistance is known to be temperature-dependent (Pierce and Wehner, 1990). Sakata et al. (2006) argued that although several commercial cultivars show resistance to powdery mildew under high-temperature conditions, there was no resistant cultivar for greenhouse production from winter to spring. Considering the quantitative disease resistance characteristic, in-depth pathogenic studies are warranted to further quantify the disease resistance to powdery mildew among the different types of cucumber cultivars under diverse environmental conditions.

Comparative resistance to two-spotted spider mites among cucumber cultivars has been previously reported (Maleknia et al., 2016). In the current study, we noticed Japanese cucumber cultivars had less leaf damage caused by two-spotted spider mites compared with the other cucumber types (Table 7). However, there was no significant difference in leaf damage caused by two-spotted spider mites among the other types of cucumbers. Plant resistance toward insect pests could be governed by plants forming characteristics that adversely affect insect biology, repel insects from the host, or tolerate insect attacks (War et al., 2012). It will be interesting to further investigate potential plant defense mechanisms of the less damaged cultivars against two-spotted spider mite attacks.