Plants.

‘Cordial’ produces an open globose plant with moderate density and moderate to strong vigor between that of the late-midseason, less vigorous cultivar Allstar (Galletta et al., 1981) and the late-season, more vigorous cultivar Ovation (Lewers et al., 2004) (Fig. 2). The Royal Horticultural Society (RHS) petiole color (Royal Horticultural Society and Flower Council of Holland, 1986) is light yellow green (RHS86 yellow-green group 144B) with moderate pubescence density, more so than ‘Allstar’ or ‘Ovation’. Leaves are uniformly composed of three leaflets. Individual leaves are slightly folded to open and medium green in color (RHS86 green group 137A upper surface, RHS86 green group 137C lower surface). The length-to-width ratio of the terminal leaflets is 1:2. The terminal leaflets averaged 28.6 apiculate leaf serrations. The tallest inflorescences produce flowers above the canopy, with primary flowers having an average of eight overlapping petals, which are slightly longer than wide and have a yellow-orange stigma color (RHS86 yellow-orange group 22A). Primary flowers have an average of 33.2 anthers per flower, which is more than those of ‘Allstar’ (24.6 per flower) and ‘Ovation’ (22.2 per flower). Stolon production at Beltsville (≈9 per plant) is greater than that of ‘Flavorfest’ (Lewers et al., 2017) (≈8 per plant), and less than that of ‘Keepsake’ (≈10 per plant), ‘Allstar’ (≈10 per plant), and ‘Ovation (≈11 per plant). Stolons have moderate levels of anthocyanin pigmentation where they are exposed to sunlight that are more than those of ‘Allstar’ and similar to those of ‘Ovation’.

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‘Cordial’ strawberry plants just before first harvest produced in an annual plasticulture system at the USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD.

Citation: HortScience 57, 2; 10.21273/HORTSCI15808-21

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Fruits.

Fruits are large, firm, glossy, and red (RHS86 red group 44A, RHS86 red group 45A) (Fig. 3). Fruits are conic to globose-conic, with no noticeable difference in shape between primary and secondary fruits. The firmly attached calyx is generally showy, larger than (primary fruit) or the same diameter as the fruit, reflexed to spreading, and positioned evenly with the top of the fruit. There is no neck, but there may be a very narrow band of fruit with no achenes below the calyx. Achenes, which are flush with the fruit surface, are red (RHS86 red group 45A) on the sun-exposed side of the fruit to yellow-green (RHS86 yellow-green group 153B) on the underside of the fruit. The interior flesh color is very evenly distributed, mostly orange-red (RHS86 orange-red group 33A, RHS86 orange-red group 33B), with a small patch of white (RHS86 white group 155D) near the proximal end. In fruits with a central cavity, the cavity is small. Vascular tissue within the fruit is barely noticeable, unlike the fruits of ‘Allstar’ and ‘Ovation’, which have clearly visible, lighter color vascular tissue radiating from the center to the achenes.

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‘Cordial’ strawberry fruits produced in an annual plasticulture system at the USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD.

Citation: HortScience 57, 2; 10.21273/HORTSCI15808-21

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Production system.

‘Cordial’, as B2360, was evaluated with other selections and cultivars on the North Farm of the USDA-ARS Henry A. Wallace Beltsville Agricultural Research Center at Beltsville, MD (lat. 39°01′48.42″N, long. 76°56′07.99″W, 49.4 m elevation), on Downer-Hammonton complex loamy sand, and on Russet-Christiana complex fine sandy loam soils (USDA-Natural Resources Conservation Service, 2020), supplemented each year with potassium, sulfur, and boron to correct deficiencies reported by annual soil tests. These soils have existing high levels of phosphorus and moderate levels of potassium. Calcitic lime was used to adjust the soil pH to 6.3 to 6.5. No fumigants were used.

Observation plots and replicated plots were established during annual plasticulture production (Black et al., 2002) using raised beds with two lines of trickle irrigation 7 cm below the surface. The plasticulture system uses black plastic mulch. Six-plant plots were established in August before each evaluation year. In 2014, only a single six-plant plot of B2360 was established and evaluated. Starting in 2015, four six-plant plots each of B2360 and other selections and cultivars were established and evaluated. Fertigation supplied nitrogen at a rate of 34 kg⋅ha⁻¹ N per year as ammonium nitrate, potassium nitrate, or calcium nitrate. No fungicides were used. Frost protection of spring flowers was provided by microsprinklers on 30.5-cm stakes (SuperNet Jr.; Netafim, Fresno, CA) when temperatures dropped below 2 °C and by overhead impact sprinklers at 1 m elevation when temperatures dropped below 1 °C.

Subjective evaluations of observation plots.

Observation plots were subjectively evaluated in October after planting for vigor, disease, and runner production during the following May for season determination, during May and June for fruit quality and fruit load, and after fruiting for a second rating of vigor, disease, and runner production. Plots were rated after planting and after fruiting for incidence and severity of unspecified crown rot, as well as powdery mildew [Podosphaera aphanis (Wallr.) U. Braun & S. Takam], leaf scorch [Diplocarpon earlianum (Ellis & Everh.) F.A. Wolf], leaf blight [Phomopsis obscurans (Ellis & Everh.) Sutton], and bacterial angular leafspot disease (Xanthomonas fragariae Kennedy and King). Individual plots were given subjective scores. A subjective score of 9.0 (best) to 0.0 (worst) was used for all traits except runner production. A score of 7.0 was considered minimum cultivar quality. Scores of 6.5 created concern, and scores of 6.0 or less were possible causes of rejection as a potential cultivar. For runner production, a different scale with scores of 0.0 (no runners) to 5.0 (too many runners) was used. Scores of 2.0 to 2.5 indicated a good balance because strong runner production is valued by matted-row growers and by nurseries propagating plants for sale, but too many runners can lead to high labor expenses for removing runners in the annual plasticulture system.

A season score was subjectively estimated each year on the morning of first harvest or the day before. The ratings were based on the amount of ripening progression from flowers to ripe fruits. The ratings were subjective, from 9 (earliest with ripe fruits) to 0 (latest with just flowers). During fruiting, observation plots were subjectively evaluated at the peak of their season for yield, size, appearance, symmetry, firmness, skin toughness (resistance to abrasion when rubbed with a thumb), skin color, flesh color, and flavor. Appearance ratings were influenced by size, symmetry, shape, uniformity, coloration (too orange, too purple, white shoulders), and signs of degradation, such as loss of glossiness, bronzing, bruising spots, sun scald, or skin-splitting from rain damage. Strawberries from the plots were rated for the specific diseases of anthracnose fruit rot (Colletotrichum acutatum J.H. Simmonds) and botrytis fruit rot (Botrytis cinerea Pers.:Fr.). To estimate sweetness and tartness, three to five fruits from each six-plant plot were hand-squeezed in the field near the peak of harvest for that genotype. The juice was measured with a Pocket refractometer PAL-1 (ATAGO USA, Inc., Bellevue, WA) to obtain estimates of the percent soluble solids and a LAQUAtwin-pH-22 (HORIBA Scientific, Edison, NJ) to obtain estimates of acidity (pH).

Replicated evaluations.

Replicated yield evaluations were made in a randomized complete block design with one replication in each of three blocks. Plots were harvested twice weekly. For each plot at each harvest, rotted fruits were harvested into containers separate from fruits that showed no sign of rot. The containers were weighed separately. These weights were used to determine the total yield, total nonrotted yield, and total rotted yield for each plot for the year adjusted for plant stand.

Ten randomly selected fruits from the container showing no signs of rot were weighed to obtain an average fruit weight for that plot and harvest. If fewer than 10 fruits were available, then the average fruit weight was determined from the number available and it was not adjusted for fruit number or plot yield. The average fruit weight across all harvest dates for a cultivar was recorded as the average fruit weight for the year for that cultivar. The average fruit weight from the date when the fruit weight was greatest was recorded as the peak fruit weight for the year for that cultivar.

From the container of fruits showing no signs of rot, the fruit were given a subjective market score from 2.0 (worst) to 9.0 (best). A score of 0.0 was reserved for genotypes that did not flower, and a score of 1.0 was reserved for genotypes that flowered but did not produce fruit. Size, shape, uniformity, glossiness, and coloration (bronzing, bruising, white shoulders) were key features when determining the market score. Market scores of 7.0 or more were given to containers with each fruit appearing suitable for fresh eating. A score of 6.5 was given to containers with most fruit appearing acceptable for fresh eating but some fruit appearing unacceptable. Scores of 6.0 or less were given to containers with more than half the fruit unacceptable for fresh eating. Faults and diseases were identified and noted for each plot at every harvest. If the market score was 7.0 or more, then the yield from that harvest of the plot contributed to the total marketable yield for the year.

For the container showing no signs of rot, up to 12 fruits were selected for shelf-life evaluation and placed in a labeled, clear, plastic egg carton with the calyx down. These fruits were selected to be free of signs of injury and relatively uniform in size, shape, and maturity. Fruits in the egg cartons were stacked in plastic egg boxes, stacked two boxes high, and covered loosely with a black plastic trash bag. The fruits were stored in a walk-in cooler set at 0.5 °C. At 1 week and 2 weeks, the numbers of fruits in each egg carton that showed signs of rot or degradation were recorded. A single fruit could be both rotted and degraded. A rotted fruit showed signs of fungal growth. Signs of degradation included desiccation, loss of gloss, dark blotches resembling bruises, a fruit turning dark, soft wet spots, soft dry spots, small depressions between achenes, and small dark depressions. In 2017 and 2018, the numbers of fruits that still appeared marketable were recorded also.

Each year’s averages across replications for total yield (g/plant), percent nonrotted yield, percent marketable yield, market score, peak fruit weight (g/fruit), average fruit weight (g/fruit), firmness, toughness, percent soluble solids, pH, and percentages of marketable, rotted, and degraded fruits at 1 week and 2 weeks were used in the analyses of variance to compare genotypes (P = 0.05) using SAS software version 9.4 (SAS Institute Inc., Cary, NC). A mixed model was used to determine if significant differences existed, with cultivar as a fixed effect and year as a random effect. A general linear model was used to obtain separations of means and least significant differences between means.

Weight.

The peak fruit weight of Cordial (31 g) was statistically similar to those of most of the other cultivars, except for Earliglow (17 g), noted for relatively small fruit but grown for its excellent flavor and early season (Table 1). ‘Cordial’ fruit weight continued to be good as the season progressed. The average fruit weight of Cordial (18 g) was statistically greater than that of any other cultivar tested, including Keepsake (13 g) and Flavorfest (13 g), known for large fruit, and Ovation (14 g) and Allstar (10 g), with seasons similar to that of Cordial (Table 1).

Table 1.

‘Cordial’ strawberry fruit traits compared with those of eight other cultivars grown in an annual plasticulture system at the USDA-ARS Beltsville Research Center, Beltsville, MD, 2015 through 2018.

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Market score.

Cordial fruit had the highest average market score (7.6), although it was statistically similar to those of the midseason cultivars, Keepsake (7.0) and Flavorfest (6.9), and of the other late-season cultivar, Ovation (7.0) (Table 1). The average market score for ‘Cordial’ fruit was statistically greater than that of ‘Allstar’ (6.5), a cultivar with a fruiting season slightly earlier than that of ‘Cordial’. In 2016, 2017, and 2018, notes recorded at harvest indicated sharply contrasting rain tolerance between ‘Allstar’ fruit and ‘Cordial’ fruit. After several significant rain events, notes recorded indicated that skin of ‘Allstar’ fruits were often cracked, split, or etched in appearance, impacting the market score. On the same harvest days, notes for ‘Cordial’ fruit included comments that it looks dry in the rain and market scores were high.

Firmness and toughness.

The subjective rating of fruit firmness showed ‘Cordial’ fruit to be very firm (8.0), similar to that of ‘Keepsake’ (7.9) and ‘Camarosa’ (7.8), known for firm fruit (Table 1). The fruit of ‘Cordial’ were statistically firmer than those of ‘Ovation’ (7.5) of the same season, and ‘Allstar’ (7.5), with a slightly earlier season than ‘Cordial’. Subjective ratings of fruit skin toughness showed ‘Cordial’ fruit to be very tough (8.0) and statistically similar to fruit of ‘Keepsake’ (8.1), ‘Galletta’ (7.8), and ‘Flavorfest’ (7.8) (Table 1).

Percent soluble solids and pH.

‘Cordial’ fruits tasted mild and pleasant, even after several days of rain. Although the cultivar quality is acceptable, subjective flavor ratings for ‘Cordial’ (7.3) were not as high as those for the highest-rated cultivars, ‘Keepsake’ (8.1), ‘Earliglow’ (7.9), and ‘Flavorfest’ (7.8). As a measure of sweetness, the percent soluble solids of ‘Cordial’ fruits (7.6%) was the same as that for ‘Flavorfest’, and statistically similar to that of the cultivars with the highest percent soluble solids, ‘Keepsake’ (8.8%) and ‘Earliglow’ (8.6%), which had the highest flavor ratings (Table 1). There were no differences among cultivars regarding the pH, which is a measure of tartness. The pH of ‘Cordial’ fruits (3.79) was relatively high, indicating it was less tart. ‘Allstar’ was the only cultivar with a higher fruit pH (3.85). A higher pH can be helpful in rainy weather with less sunshine, when fruit sugars tend to be lower; fruit with low sugar and low pH taste very tart. Notes taken at harvests in the rain and after rain indicated that ‘Cordial’ fruits did not taste overly tart and that they instead had a pleasant taste.

Postharvest quality.

‘Cordial’ and ‘Keepsake’ had significantly higher percent marketable fruits than all the other cultivars (Fig. 6A) at both 1 week and 2 weeks after harvest in 2017 and 2018, the only years when data were collected for this trait. At 1 week, ‘Cordial’ had 86% marketable fruit and ‘Keepsake’ had 91% marketable fruit; ‘Earliglow’ had the next highest rate of marketable fruit (54%). At 2 weeks, both ‘Cordial’ and ‘Keepsake’ had 52% marketable fruit. The percent degraded fruits at 1 week for Cordial was 26%, which was statistically similar to that of ‘Keepsake’ (29%), the first cultivar resulting from the increased effort at Beltsville to improve postharvest quality, and to that of ‘Ovation’ (47%), the other late-season cultivar (Fig. 6B). The percent degraded ‘Cordial’ fruits at 2 weeks (50%) was statistically similar to that of ‘Keepsake’ (62%) and ‘Ovation’ (67%). Notes recorded during evaluation indicated that all cultivars showed some degree of the following types of degradation: desiccation, loss of gloss, soft wet spots, soft dry spots, small depressions between achenes, and small dark depressions. Additionally, notes indicated that ‘Chandler’ and ‘Camarosa’ fruits displayed color changes not seen on the other cultivars. After 1 week in storage, 81% of ‘Chandler’ fruits and 93% of ‘Camarosa’ fruits were degraded, primarily because of these color changes. ‘Chandler’ fruits often turned dark evenly over the entire fruit, and ‘Camarosa’ fruits often had large dark blotches resembling bruises, many of which were located in places unlikely to have been caused by rough handling. The percent rotted ‘Cordial’ fruits at 2 weeks was 14%, which was statistically similar to that of all other cultivars except ‘Flavorfest’, which had a higher portion of decayed fruits (38%) (Fig. 6C). The portion of decayed fruits at 1 week was statistically similar for all cultivars.

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‘Cordial’ strawberry fruit percent marketable (A), percent degraded (B), and percent rotted (C) after 1 week and after 2 weeks in refrigerated storage at 0.5 °C. Cordial was compared with eight other cultivars grown in an annual plasticulture system at the USDA-ARS Beltsville Research Center, Beltsville, MD, from 2015 through 2018. The numbers in parentheses indicate the number of years of data collected for each cultivar–trait combination. At each harvest, fruits without any visible flaws were placed in clear plastic egg cartons and refrigerated. The numbers of marketable, rotted, and degraded fruits are counted at 1 week and 2 weeks after harvest. The average for each trait–cultivar combination for each year was used in an analysis of variance. Cultivars with different letters indicate statistically significant differences between cultivars.

Citation: HortScience 57, 2; 10.21273/HORTSCI15808-21

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