Abstract
In the floriculture trade, cut pepper (Capsicum annuum) stems are typically grown for their fruit to add color contrast to the foliage and blossoms of conventional floral arrangements. Stems are commonly stripped of foliage because leaves wilt rapidly. Three divergent plant types and commercial hydration protection spray products were evaluated to identify effective vase life treatments and new pepper lines that combine both fruit and foliar interest with an acceptable postharvest cut stem life. Three inbred US Department of Agriculture pepper breeding lines with a tall vigorous growth habit and black foliage were selected for evaluation as cut stems. Line 190-2 produced upright, tabasco-like fruit; 191-1 produced upright, clustered, round fruit; and 196-1 was fruitless. Three commercial spray treatments Crowning Glory (FLCG), Finishing Touch, and Aqua Finish Clear (AFC) were evaluated on treated cut stems stored at 10 and 23 °C. The pepper breeding line had the greatest influence on cut stem foliage and fruit vase life. The fruitless line, 196-1 exhibited an extended vase life in comparison with fruited lines. Cold storage extended the vase life of cut stems. FLCG reduced foliage vase life at 23 °C, and AFC extended foliage vase life of the fruitless line 196-1. Relative to foliage, fruit exhibited greater resistance to desiccation, with glossier fruit of 191-1 desiccating more rapidly than fruit of 190-2. Similar trends were noted when cut stems were stored at 10 °C for 7 days and moved to 23 °C. However, in 2022 trials, the vase life of 190-2 was shortened, and those of 191-1 and 196-1 were extended, highlighting the influence of preharvest factors on vase life. The results demonstrate that cut stems of new pepper lines with vigorous upright growth habits and black-pigmented foliage, together with diverse fruit morphology, provide innovative possibilities for stunning cut flower arrangements.
Considerable morphological diversity exists within pepper (Capsicum annuum) germplasm for fruit and leaf shapes, size, color, and plant habit. Ornamental pepper fruit range from small piquin-size fruit to full-size chiles with immature color varying from green to yellow to ivory or lilac to dark purple to black. Ripe fruit color may vary from yellow to orange to red, with novel variants including brown. Pepper leaf color can be green, purple, black, or variegated green/white or green/yellow (Stommel and Bosland 2006). Similar to the extensive diversity for pepper fruit and leaf color, leaf morphology can range from long and narrow to rounded with smooth or frilly margins or rugose when mature. Plant habit ranges from short and compact to as tall as 3 to 4 ft.
Pepper diversity is the basis for multiple market classes of culinary pepper and has allowed myriad opportunities to develop unique ornamental peppers (Stommel and Bosland 2006). Ornamental peppers are commonly grown for the pot plant market and for use as bedding or garden plants because their colorful fruit and foliage may provide year-long interest in the home and garden. This market class of peppers is also commonly used to make strings of dried peppers called ristras (Bosland et al. 1990). Pepper cut stems have been popular in Europe and are increasing in popularity in the United States (Stommel and Bosland 2006). Cut pepper stems are typically grown for their fruit to add color contrast to the foliage and blossoms of conventional floral arrangements.
In the floriculture trade, use of pepper for cut stems commonly involves stripping stems of foliage because green foliage wilts rapidly, making it unsightly in floral displays even though acceptable fruit quality appearance is maintained (Dole et al. 2017). The expected vase life of ornamental peppers is 7 to 10 d, but it can vary greatly depending on the cultivar, fruit size, fruit count, and preharvest and postharvest production conditions. Foliage may be stripped manually, but larger-scale stem defoliation is efficiently accomplished via sweating. Dry cut stems are stored in a dark insulated box in the greenhouse or other environment where temperature can be maintained at 32/20 °C (day/night) for up to 4 d or when foliage readily abscises. Cut pepper stems are held in water without a hydrating product before packing. Clark et al. (2010) found that use of a commercial hydrator in storage water reduced the vase life or had no effect on cut pepper stems. Use of a holding preservative in water yielded inconsistent results for extending the vase life of cut pepper stems, with some cultivars responding positively and others exhibiting no treatment effect. Supporting observations that water uptake of cut stems is greatest immediately after harvest (Doi et al. 1999), no differences were found between storage in holding solutions for 2 d or until termination of cut stem vase life for some plant groups. Clark et al. (2010) reported that for cut pepper stems and most of the other 121 plant groups evaluated, hydrator solutions, holding preservative solutions, and control water treatments produced similar vase life or holding preservative treatment extended vase life. Pepper foliage wilted readily among treatments, whereas fruit quality was maintained. de FM Franca et al. (2017) similarly reported that hydrator solutions reduced or had no effect on the vase life of cut pepper stems, and that holding solutions had a positive effect but was cultivar-dependent. Whereas hydrator and holding floral preservative solutions have been well-studied, reports of spray solutions for extending the vase life of cut stems are limited (Daly 2020; Ranwala 2010, 2013).
Consumer interest in dark purple to black-pigmented garden plants has been sustained over two to three decades by the introduction of dark-leaved coral bells (Heuchera sanguinea), black-pigmented sweetpotato vine (Ipomea batatas), and the All-American Selection ‘Black Pearl’ pepper (Armitage 2002; Platt 2004; Stommel and Griesbach 2005). Black foliage ornamental peppers, including Midnight CreeperTM, Pepper JackTM, Lil’ PumpkinTM, and Solar EclipseTM, further combine black-pigmented pepper foliage with the extensive variation available within pepper germplasm for fruit, foliage, and plant habit (Stommel and Griesbach 2008a, 2008b). Breeding lines with tall stature, multiple basal shoots, diverse fruit attributes, and black foliage provide renewed interest in utilization of pepper for use as cut stems. Based on observations of the US Department of Agriculture pepper breeding lines in field and potted production conditions and preliminary cut stem observations, we evaluated three divergent cut stem plant types and commercial hydration protection spray products to identify alternative vase life treatments and new pepper lines that combine both fruit and foliar interest with acceptable postharvest cut stem life.
Materials and methods
Plant materials
Three inbred US Department of Agriculture pepper breeding lines with black foliage exhibiting variations of fruit and leaf morphology were selected for evaluation as cut stems for floral application. These lines were selected from field observation trials conducted at the Beltsville Agricultural Research Center in Beltsville, MD, USA and at Seaberry Farm, Federalsburg, MD, USA. The experimental lines have a tall stature with greater than three basal shoots and a branching growth habit. Fruit of line 190-2 are tabasco-like, upright, solitary, black when immature, and orange when mature (Fig. 1A–C). Line 191-1 is a taller more vigorous selection from early generations leading to development of ‘Black Pearl’ (Stommel and Griesbach 2005). Line 191-1 produces upright clusters of black round fruit that mature to red (Fig. 2A–C). Line 196-1 is a true-breeding seed-propagated line derived from the clonal form of ‘Solar Eclipse’ (Stommel and Griesbach 2008b). Line 196-1 is a presumed photomorphogenic mutant that flowers under short days and, consequently, lacks fruit throughout the growing season up to first frost in the mid-Atlantic region of the United States, exhibiting an indeterminate growth habit and smaller leaves than ‘Solar Eclipse’ (Fig. 3A–C). Foliage of 191-1 is similar to that of ‘Black Pearl’ (glossy and fully expanded leaves), and leaves are larger than those of 190-2 and 196-1 (leaf length/width ∼4.5/2.5, ∼8.5/4.0, and ∼4.2/2.1 cm for 191-1, 190-2, and 196-1, respectively). Under field conditions, plant height potentials for 190-2, 191-1, and 196-1 are, on average, 28.75, 31.5, and 36.75 inches, respectively.
Leaf and fruit wilt and gloss scores for pepper line 190-2. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf and fruit wilt and gloss scores for pepper line 190-2. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf and fruit wilt and gloss scores for pepper line 190-2. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf and fruit wilt and gloss scores for pepper line 191-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no leaf drop; 1 = minor leaf drop; 2 = moderate leaf drop; 3 = complete leaf drop. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf and fruit wilt and gloss scores for pepper line 191-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no leaf drop; 1 = minor leaf drop; 2 = moderate leaf drop; 3 = complete leaf drop. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf and fruit wilt and gloss scores for pepper line 191-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage and fruit. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf and fruit wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf and fruit wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Solid lines denote leaf wilt and gloss; dashed lines denote fruit wilt and gloss. Leaf wilt: 0 = no leaf drop; 1 = minor leaf drop; 2 = moderate leaf drop; 3 = complete leaf drop. Fruit wilt: 0 = no visible desiccation; 1 = fruit shriveled, peduncle turgid; 2 = fruit shriveled, peduncle drooping. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf wilt and gloss scores for pepper line 196-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf wilt and gloss scores for pepper line 196-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Leaf wilt and gloss scores for pepper line 196-1. (A) Pot-grown plant in the 2020 trial. (B) Field-grown plant in the 2022 trial. (C) Floral arrangement featuring foliage. Cut stems were sprayed to the point of runoff with commercial hydration protection products Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloraLife), and Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Controls were sprayed with deionized water (control). The 2020 leaf wilt and gloss scores for cut stems treated and stored at (D) 10 °C (50.0 °F) and (E) 23 °C (73.4 °F). (F) The 2022 leaf wilt and gloss scores for stems held at 10 °C for 7 d and then transferred to 23 °C. Each point represents the mean of observations for 15 cut stems. Leaf wilt: 0 = no wilt; 1 = slight wilt/tip droop; 2 = moderate wilt/droopy leaves; 3 = complete wilt/leaves flaccid. Error bars denote SE. A horizonal reference line at a wilt score of 2 denotes the threshold at which stems are no longer acceptable for use.
Citation: HortTechnology 33, 2; 10.21273/HORTTECH05144-22
Transplants of each line were grown in the greenhouse in 128-cell plastic trays with peat-based growing mix (Pro-Mix FPX; Premier Tech Horticulture USA, Quakertown, PA, USA) under day and night temperatures of 21 to 26 °C and 16 to 18 °C, respectively. After cotyledon emergence, plants were fertilized with a balanced calcium/potassium nitrate-based formulation at 50 ppm nitrogen (N) every 2 to 3 d and at 100 ppm N every 3 to 4 d throughout true leaf emergence before transferring plants to an outside coldframe 1-week before transplanting (Rutgers University 2022). For cut stem trials at the Beltsville Agricultural Research Center (lat. 39°01′50.8″N, long. 76°55′52.4″W), three 6-week-old plants of each line were transplanted to peat-based growing mix (Pro-Mix HP, Premier Tech Horticulture USA) in 3.8-gal pots on 19 Jun for Summer 2020 outdoor production. Plants were fertilized weekly with a balanced calcium/potassium nitrate-based formulation at 100 ppm N. Weather parameters during the growing period were recorded for trial 1 (mean daily temperature, 23.1 °C; maximum, 29.0 °C; minimum, 17.9 °C; mean daily solar irradiance, 199.7 W⋅m−2; total rainfall, 48.7 cm) and trial 2 (mean daily temperature, 21.8 °C; maximum, 27.8 °C; minimum, 16.6 °C; mean daily solar irradiance, 184.3 W⋅m−2; total rainfall, 52.7 cm). For 2022, trials evaluated the potential influence of a field production environment on postharvest life of cut stems. Plants were transplanted to the field on 31 May at the Beltsville Agricultural Research Center. Field soil was Keyport fine loam, which is a clayey, mixed, mesic Acquic Hapludult. Field-grown plants were spaced at 18-inch intervals in single rows on polyethylene-covered raised beds, with beds positioned on 5-ft centers with trickle irrigation. Pest control and fertilizer regimes in the field followed horticultural practices recommended for pepper production in the mid-Atlantic region of the United States (Rutgers University 2022). Beginning with early plant vegetative growth through fruit development, fertilizer was applied weekly via fertigation for a total of 75 lb N and 104 lb K over the growing season. Weather parameters were recorded (mean daily temperature, 24.3 °C; maximum, 30.5 °C; minimum, 18.4 °C; mean daily solar irradiance, 223.5 W⋅m−2; total rainfall, 30.0 cm).
Treatments
Cut stems 14 to 18 inches in height, with immature black fruit for fruited lines, were harvested in the morning before onset of hot temperatures and immediately held under shade in buckets with tap water before treatment with commercial hydration protection spray products. For 2020 trials, stems were collected on 7 Oct, and again on 28 Oct. Stems from 2022 trials were collected on 16 Aug. Foliage of 30 cut stems of each line were thoroughly sprayed using a pump sprayer to the point of runoff with premixed solutions of Clear Crowning Glory (FLCG; FloraLife, Walterboro, SC, USA), Finishing Touch (FLFT, FloralLife), or Aquafinish Clear (AFC; Syndicate Sales, Kokomo, IN, USA). Control cut stems were sprayed with deionized water. For 2020 trials, 15 treated cut stems of each line for each treatment were held at either 10 or 23 °C in 1-gal buckets with a daily change of tap water throughout the evaluation period. Temperature conditions reflected the recommended 10 to 13 °C storage and shipping conditions and average 23 °C end-user temperature conditions (Dole et al. 2017). The 2020 evaluations included two consecutive experimental replicates. In 2022 trial, we evaluated the potential influence of cold storage on the postharvest life of cut stems after transfer to 23 °C. A single experimental harvest was conducted with treated cut stems held at 10 °C for 7 d, and then transferred to 23 °C storage for the duration of the evaluation period to simulate grower to consumer conditions.
Cut stem evaluation
Treated cut stems stored at 10 and 23 °C were scored daily for leaf wilt, fruit desiccation, and leaf and fruit gloss. For lines 190-2 and 196-1, leaf wilt was recorded as 0 (no wilt), 1 (slight wilt/tip droop), 2 (moderate wilt/droopy leaves), and 3 (complete wilt/leaves flaccid). Line 191-1 exhibited leaf abscission with increasing time in storage with leaf wilt less commonly observed for this line. Leaf scores for 191-1 were recorded as 0 (no leaf drop), 1 (minor leaf drop), 2 (moderate leaf drop), and 3 (complete leaf drop). A score of 2 for either leaf wilt rating scale is representative of product that is no longer presentable in the retail market. For the purposes of presentation and discussion, leaf wilt is used synonymously with leaf drop. Fruit was scored as 0 (no visible desiccation), 1 (fruit shriveled, peduncle turgid), and 2 (fruit shriveled, peduncle drooping). Product with a score of 1 is considered no longer presentable in the retail market. Leaf wilt scoring was ended when 50% of stems exhibited leaf scores of 3. Fruit wilt scoring was ended when 50% of stems exhibited fruit scores of 1 or more. For 2022 trials, fruit scoring was ended when 50% of stems exhibited leaf scores of 3; these were discarded.
Gloss of interveinal surfaces of fully expanded leaves and epidermal surfaces at the midpoint between the blossom and stem end of black fruit were measured using a gloss meter (Microgloss 60° XS; BYK-Gardner, Wesel, Germany) calibrated to a black glass standard with a nominal value of 95.7 gloss units or 9.57% reflectance.
Data analysis
The variables leaf wilt, fruit wilt, leaf gloss, and fruit gloss were analyzed as two-factor mixed models using statistical software (R version 4.1.2) (R Core Team 2021); foliar treatment and days after cutting were used as the factors. The assumptions of the models were checked. Values that were probable outliers were reviewed in the master data set and omitted from the analyses. The variance grouping technique was used to correct variance heterogeneity. Means comparisons were performed using Sidak adjusted probability values so that the experiment-wise error was 0.05.
Results
The three pepper lines selected for evaluation as cut stems varied in leaf size and presence or absence of fruit; fruited lines also varied in solitary and clustered fruit. Within each line, significant differences between foliar treatments were evident, and cut stem leaf wilt and leaf gloss changed significantly over the storage period at both 10 and 23 °C conditions for trial 1 in 2020 (Table 1). Significant foliar treatment × days after cutting suggested that treatments varied in their efficacy over time to delay leaf wilt of cut stems. Similar trends within pepper lines for treatment efficacy and plant performance were observed in the 2020 trial 2 for leaf wilt and gloss (data not shown). During the 2022 field trials, the main effects for leaf wilt and leaf gloss were also significant at 23 °C (Table 2). For fruit-bearing lines 190-2 and 191-1, extended storage in 2020 trials at 10 °C delayed the onset of leaf wilt up to 10 d; thereafter, leaf wilt increased sharply across all treatments to moderate levels (leaf wilt score of 2) for line 191-1 (Figs. 1D, 2D). Except for cut stems treated with AFC, an increase to moderate leaf wilt scores at 10 °C was delayed to day 14 for 190-2. Similar trends for 190-2 and 191-1 were observed at 23 °C, with leaf wilt progressing more rapidly for 191-1 in comparison with 190-2 (Figs. 1E, 2E). Moderate levels of foliar wilt were generally observed within 6 to 7 d for both lines at 23 °C. During 2022 trials, foliar wilt progressed more rapidly in 190-2 in comparison with 191-1, particularly with the FLCG treatment (Figs. 1F, 2F). Foliar wilt of the fruitless line, 196-1, was markedly delayed relative to 190-2 and 191-1 at both storage temperatures during 2020 pot trials and 2022 field trials. Moderate wilt was not observed until 21 to 28 d during extended storage at 10 °C, depending on the foliar treatment (Fig. 3D). During 2022 trials, before the transfer of cut stems from 10 to 23 °C, leaf wilt was not observed in 196-1 during the 7-d 10 °C storage period (Fig. 3F). At 23 °C, moderate wilt for 196-1 was generally not evident during 2020 trials until after 8 to 12 d of storage, and it was delayed up to 18 d for stems treated with AFC (Fig. 3E). During 2022 trials, moderate leaf wilt was not observed until 20 d (Fig. 3F). Similar to 2020 trials, AFC delayed onset of moderate wilt in comparison with other treatments. Among foliar treatments, FLCG markedly reduced storage life of cut stems significantly at 23 °C for all pepper lines. At 23 °C, clear benefits of FLFT and AFC applications relative to the control in delaying moderate leaf wilt were not evident; however, AFC treatment delayed onset of leaf wilt of 196-1 by several days.
Two-way analysis of variance F values for leaf wilt, fruit wilt, leaf gloss, and fruit gloss scores of cut pepper stems from the 2020 outdoor pot trial 1 for lines 190-2, 191-1, and 196-1 stored at 10 or 23 °C (50.0 or 73.4 °F). The variables leaf wilt, fruit wilt, leaf gloss, and fruit gloss were analyzed as two-factor mixed models using statistical software (R version; 4.1.2) (R Core Team 2021), with foliar treatment and days after cutting (DAC) as the factors. Means comparisons were performed using Sidak adjusted probability values so that the experiment-wise error was 0.05. The degrees of freedom varied for each treatment because of the differing storage life of cut stems and resulting durations of data collection.
Observed declines in leaf gloss of fruit-bearing lines 190-2 and 191-1 in 2020 and 2022 trials were greater over the course of the 23 °C storage period relative to that at 10 °C (Figs. 1D–F, 2D–F). In contrast, relative declines in leaf gloss of 196-1 at 23 °C were similar to those observed at 10 °C (Fig. 3D–F). Marked differences among commercial treatments were not observed; however, FLCG imparted higher gloss readings for all lines in cut stems stored at both 10 and 23 °C. Declines in leaf gloss measurements were generally coincident with increasing leaf wilt scores. Supporting our casual observations, line 191-1 had the highest leaf gloss scores across trials.
Relative to leaf wilt, fruit of line 190-2 were quite resistant to desiccation, exhibiting very little wilt until ∼20 d at 23 °C (Fig. 1E). The three commercial spray treatments extended fruit longevity up to an additional 6 d at 23 °C. The main effects for fruit wilt and days after cutting in 190-2 at both storage temperatures were significant in 2020 trials but not significant in 2022 trials (Tables 1, 2). Commercial treatments negatively influenced fruit wilt of 191-1 at 23 °C relative to the control (Fig. 2E). Fruit of the control maintained relatively low wilt scores for ∼15 d at 23 °C. Storage of cut stems at 10 °C delayed the onset of fruit wilt in excess of 30 d for both fruited lines. In 2022 trials, fruit wilt was not observed during the 7-d 10 °C storage period, and it remained low at 23 °C for the duration of the cut stem evaluations until 50% of stems exhibited leaf scores of 3 and were discarded (Figs. 1F, 2F). Similar to leaf gloss, line 191-1 exhibited glossier fruit than 190-2 in both 2020 and 2022 trials (Figs. 1D, 1E, 2D, 2E). Fruit gloss scores declined more rapidly at 23 °C storage in comparison with 10 °C storage. Effects of spray treatments on fruit glossiness were inconsistent across pepper lines and storage temperatures.
Two-way analysis of variance F values for leaf wilt, fruit wilt, leaf gloss, and fruit gloss scores of cut pepper stems from the 2022 field trial for lines 190-2, 191-1, and 196-1. Cut stems were held at 10 °C (50.0 °F) for 7 d and then transferred to 23 °C (73.4 °F). The variables leaf wilt, fruit wilt, leaf gloss, and fruit gloss were analyzed as two-factor mixed models using statistical software (R version 4.1.2) (R Core Team 2021), with foliar treatment and days after cutting (DAC) as the factors. Means comparisons were performed using Sidak adjusted probability values so that the experimentwise error was 0.05. The degrees of freedom varied for each treatment because of the differing storage life of cut stems and resulting durations of data collection.
Discussion
Our results demonstrate that the pepper type has the greatest influence on the vase life of cut pepper stems, and that hydration protection sprays provided little or no benefit for extending the vase life of foliage or fruit. These conclusions are based on days to development of moderate leaf wilt for 50% of cut stems; at that point, the product would be no longer presentable and discarded.
For some pepper cut stem breeding lines, commercial treatments decreased foliage and/or fruit life markedly in storage, particularly at room temperature. Black foliage pepper lines tolerated cold storage, as evidenced by extended foliage and fruit longevity at 10 °C. Cut stems are typically stored in cold conditions to slow metabolic processes and preserve stem vase life (Dole et al. 2017). Storage temperatures that are higher than recommended during shipping and storage of cut flowers reduced product quality and shortened vase life (Reid and Jiang 2012). Tolerance of cut pepper stems to cold storage is economically important for product distribution and transport and holding of cut stems at points of retail sale. When stored at room temperature or held under cold conditions before removal to room temperature conditions, stems bearing fruit exhibited acceptable foliage vase life up to 10 to 12 d at 23 °C before the onset of moderate leaf wilt. Foliage of the fruitless line, 196-1, exhibited greatly extended foliar vase life in cold storage and at room temperature. Leaf senescence was delayed in fruitless stems. Developing fruit are strong sinks that compete for plant assimilates. Fruitless stems had reduced metabolic and water needs associated with fruit development, which may contribute to the maintenance of extended foliage vase life. When stems are cut, sucrose import to sink tissues of cut flowers is markedly reduced (Da Silva 2003). Sugars added to vase solutions may extend the vase life of some cut flowers by helping to maintain the respiration rate of floral tissues.
Line 191-1 had large leaves in comparison with 190-2 and 196-1 and exhibited leaf abscission with increasing days after cutting in comparison with leaf wilt observed for 190-2 and 196-1. Effects of ethylene on leaves and fruit of ornamental peppers vary greatly among species and cultivars. A clear relation between leaf abscission and ethylene production has been established (Jackson and Osborne 1970). Treatments with ethylene blockers may reduce leaf abscission. Potted pepper plants sensitive to ethylene that were treated with 1-methylcycloproprene and subsequently exposed to ethylene displayed reduced leaf abscission in comparison with untreated plants (Santos et al. 2015; Segatto et al. 2013). Ethylene-sensitive plants may also exhibit premature senescence symptoms, including leaf desiccation or necrosis (Iqbal et al. 2017). de FM Franca et al. (2017) found that ethylene blockers had minimal effects on the vase life of cut pepper stems. Other plant hormones, including gibberellic acid and cytokinins, can delay wilting of ethylene-sensitive and ethylene-insensitive cut flowers (Eason 2002; Trivellini et al. 2015).
Studies were performed beyond the onset of moderate leaf wilt to further assess the longevity of cut pepper stem fruit. Well beyond the foliage vase life, pepper fruit on cut stems exhibited extended vase life of ∼15 to 20 d at room temperature and in excess of 30 d under cold storage conditions. Fruit desiccation was observed after extended storage beyond this period. Fruit abscission did not occur in 190-2 or in 191-1 when leaf abscission was observed with extended storage.
Line 191-1 displayed higher leaf and fruit gloss scores in comparison with 190-2 and 196-1. Line 191-1 fruit vase life was reduced by ∼5 d at 23 °C in comparison with fruit of 190-2. More rapid onset of fruit desiccation in 191-1 may be explained, in part, by higher gloss attributed to reduced wax deposition on the fruit surface, resulting in increased tissue water permeability. It was not possible to evaluate a similar trend for gloss in foliage when comparing 190-2 and 191-1 because foliage of 191-1 was prone to abscise instead of wilt. In pepper fruit, a negative relationship exists between water loss and epicuticular wax content (Lownds et al. 1993). Gloss mutants have been associated with the suppression of the wax biosynthetic pathway, leading to reduced fruit, stem, and leaf depositions of cuticular waxes that limit nonstomatal water loss and gas exchange (Leide et al. 2007; Pu et al. 2013).
Our trials highlight the importance of preharvest conditions to the vase life of cut pepper stems. Vase life of 190-2 was shortened, and vase life of 191-1 and 196-1 was extended in the 2022 trials in comparison with the 2020 trials. Production methodology varied between trials, as did environmental conditions. The main season 2022 cut stem harvests positively influenced the stem life of two of the three black foliage lines evaluated. It is difficult to generalize the optimal preharvest conditions required for extended vase life. Higher precipitation and an extended season in 2020 may have contributed to reduced vase life for some lines relative to the 2022 performance. Differences in plant health or vigor were not apparent between pot and field plant cultures. Light intensity and temperature have been well-studied for their effects on the postharvest life of cut flowers. However, whereas high light intensity optimizes the plant carbohydrate status and may have a positive effect on vase life, higher temperatures typical under such conditions in the field may increase respiration and reduce carbohydrate reserves (Vehniwal and Abbey 2019). More controlled studies are required to draw inferences regarding the influence of ambient light conditions on the vase life of cut pepper stems. Regarding traditional cut flowers, preharvest crop maturity may influence the vase life. Harvest at early stages of flower development positively influences the vase life of some ornamentals (Ahmad and Dole 2014). Preharvest pepper fruit maturity can influence the cut stem vase life, but the results may be dependent on the plant type. After evaluating two pepper cultivars, de FM Franca et al. (2017) found that stems of one cultivar harvested with less mature fruit had a longer vase life than stems with fully mature fruit; however, the vase life of the second cultivar was unaffected by the harvest stage. Postharvest handling had the most consistent influences on vase life in that study.
Our results demonstrate the importance of plant type to the selection of peppers for cut stems. The current commercial recommendations of stripping leaves from cut stems at harvest should not be applied uniformly to diverse lines because foliage of some selections exhibits an acceptable vase life at room temperature. Under varied outdoor pot and open field cultures, the evaluation of our three divergent pepper plant types suggested that cut stems may be used for the display of only fruit, display of fruit and foliage, or display of only foliage. An extended foliage vase life is possible with fruitless plants. The application of protective sprays to cut pepper stems did not result in a marked extension of foliage or fruit vase life. However, exceptions did occur for both fruit and foliage, depending on the plant type, with some products shortening and other products extending the vase life. Cut stems of new pepper lines with vigorous upright growth habits and black-pigmented foliage, together with diverse fruit morphology, provide innovative possibilities for stunning cut flower arrangements when combined with vibrant reds, yellows, and oranges.
Units
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