Short-day Strawberry Research Articles

Delaying Flowering in Short-Day Strawberry Transplants with Photoselective Nets

Growing strawberry (Fragaria x ananassa Duch.) transplants under photoselective nets delayed flowering. In August, ‘Strawberry Festival’ strawberry plug plants were grown under red or blue ChromatiNet® or without shading (control) in a glasshouse. Fall flowering response was determined following transplanting into a plasticulture system in the field. The no-shade control plants began flowering in late September and by late November, more than 90% of the plants had bloomed. These plants produced fruit from October to early January. Flowering in plants that were grown under red- or blue-colored shade net did not occur until early January. The results of this study suggested that the use of photoselective shade nets over strawberry plug plants in August blocks the light signal that initiates flowering until the netting is removed, hence, delaying the initiation of flower buds until plants are transplanted in the field.

‘Valley Sunset’ Strawberry

‘Valley Sunset’, a short-day strawberry (Fragaria ·ananassa Duchesne ex Rozier), was commercially introduced in Canada in May 2009 by the Atlantic Food and Horticulture Research Center of Agriculture and Agri-Food Canada (AAFC). ‘Valley Sunset’ produces medium yields of very large, sweet-tasting fruit ripening in the late season offering growers a cultivar to extend the harvest season beyond that of ‘Cabot’ and ‘Bounty’.

FLOWER BUD FORMATION IN SHORT-DAY STRAWBERRY CULTIVAR UNDER NON-PHOTO INDUCTIVE CONDITIONS

A scheme for producing short-day type strawberry cultivars that initiate flowers under long-day photoperiod was used to investigate the flower bud induction. When runner tips of short-day type 'Carmine' were started as plug plants in early July and field planted 1 September 86% of transplants flowered by mid October. When the July-plugged transplants were retained in tray flats at high plant density during July and August the leaves formed a full canopy or high leaf area index above the plant crowns and the crown near the base of leaf petioles was completely in the shade. A spectral analysis showed that wavelengths less than 700 nm did not reach the crown because of chlorophyll absorbance. Illuminating the crown for 16 h·day -1 for 4 weeks in August with 662 nm light decreased transplants that flowered by mid October. The results suggest that fall-flowering transplants of short-day strawberries were produced by rooting runner tips in early July and having a plant canopy that alters the quality of light that illuminates the crown.

DEVELOPMENT OF STRAWBERRY BREEDING LINES WITH EXTENDED DORMANCY

The short-day cultivar 'Judibell' emerges from dormancy 4-5 weeks later than most other strawberry cultivars and crops around 35 days later than the industry standard, 'Elsanta'. The inheritance of this trait was investigated by intercrossing 'Judibell' with five late and mid-season genotypes in all combinations including selfs, but without reciprocals (half-diallel). Twenty-five seedlings from each of the 21 families (totalling 525) were planted in the field in a randomised block design. The plants were over-wintered and assessed the following year. The seedlings were evaluated weekly for date of emergence from dormancy and date of first flower. Assessment of the progeny indicated that there was segregation in the seedling population for both duration of dormancy and flowering time. These two traits were found to be highly heritable and independent of one another. Inheritance was concluded to be quantitative and additive, as there was no evidence of segregation to suggest that either was under the control of a single major gene. Whilst all the 'Judibell' selfed seedlings had long dormancy, not all had the later flowering trait. This suggests, therefore, that this line does not have the ideal genetic combination to flower as late as possible. By careful selection of parents it may be possible to combine a more extreme expression of long dormancy and late flowering to develop short-day strawberries with an even later fruiting period than the cultivar 'Judibell'. Seedlings with a very late season were selected from the half-diallel progeny and backcrossed to 'Judibell' and another, related line. The seedlings were evaluated, as before, for date of emergence from dormancy and flowering date. Whilst one family contained individuals with a longer average dormancy, another contained plants which flowered the latest. This finding provides further evidence that the two traits are independently inherited.

Light-emitting Diodes for Manipulating the Phytochrome Apparatus

Light-emitting diodes (LEDs) are solid-state, long-lived, durable sources of narrow-band light output that can be used in a range of horticultural and photobiological applications. LED technology is rapidly developing and high-quality, high-output LEDs are becoming commercially available at an affordable cost. LEDs provide the opportunity to optimize the spectra for a given plant response, but consideration must be given to both photosynthetic and photomorphogenic effects of light while making those selections. A discussion of basic phytochrome response and data necessary to select narrow-band LEDs to achieve a specific photostationary state is provided. The use of LEDs to alter spectral quality, and phytochrome equilibrium, to regulate anthocyanin formation in red leaf lettuce and to regulate flowering of short-day strawberry are discussed.

Relationships between yield components in first cropping year and average yield of short-day strawberries over two main seasons

Fruit productivity of the garden strawberry, Fragaria × ananassa Duch., is a result of interrelationship of yield components contributing to it directly or indirectly. The main aim of the investigation was to find out whether there exists any general regularity, connecting relationships between main yield components in first cropping year to average yield of two main seasons. Two successive studies which primarily included 23 genotypes, differing in yield components and productivity, each, were planted in field conditions in spring 1999 and in spring 2000, respectively, and used for data collection to explore the material obtained in them. Four key yield components and average yields were measured in both cropping years, after which all possible ratios between the components were calculated to find out: first, the relationships to be influential on average yield of the two main seasons; second, type of the probable yield dependence upon the ratios; and, third, their values leading to high yields. Two ratios between the key yield components in first season, i.e.: inflorescence number per plant to branch crown number per plant, named ratio 1, and fruit weight (g) to flower count per inflorescence, named ratio 2, have been found to be related to average yield. An irregular surface, with a single peak falling approximately in its centre, describes average yield dependence upon the ratios. Values of the two ratios falling in the range of 1.0–1.6 each, provided that they are close, have enabled plants to produce high yields cumulatively over two first years. The paper highlights the most important differences in plant behaviour and yield dynamics of strawberry genotypes, depending on combinations of the ratios in first year, discerning those, which have been particularly advantageous to obtain very high yields, and are influenced by negative environmental factors least of all. Based on the findings, a method of predicting of average yield has been developed. Following this, usefulness of the method and possibilities of its using in strawberry breeding and variety trial are discussed.

‘Rubygem’ Strawberry

‘Rubygem’, a new short-day strawberry (Fragaria ×ananassa Duch.), produces high yields of moderately firm, attractive well-flavored fruit from late autumn through early spring in the strawberry-growing district in Southeast Queensland. ‘Rubygem’ is recommended for trial in areas with mild winter climates, especially where rainfall is unlikely and a well-flavored berry is required.

Effects of Runner Tip Size and Plugging Date on Fall Flowering in Short-Day Strawberry (Fragaria × ananassa Duch.) Cultivars

Producing strawberry transplants from runner tips that were plugged ∼1 month earlier (early July) than the standard time (early August) promoted fall flowering in some short-day strawberry cultivars. In 2002,100% of ‘Chandler’ transplants produced in early July flowered in the fall, but none of the August-plugged ‘Chandler’ transplants flowered in the fall. In 2003, 73% of ‘Chandler’ transplants produced in mid-July from average-size runner tips and less than half of transplants from small-size runner tips flowered in the fall. Again, August-plugged plants did not flower in the fall. Flowering was absent in ‘Northeaster’ plants. Under protected cultivation, July-plugged ‘Sweet Charlie’ plants bloomed earlier and produced more fruit in November and December than those plugged in August. This study showed that fall flowering in ‘Chandler’ and ‘Sweet Charlie’ strawberry is possible if the transplants are prepared by plugging runner tips in early July. This novel technique for propagating strawberry transplants for annual plasticulture combined with production under high tunnels creates an opportunity for strawberry production in early winter and again in the spring (double cropping) in the mid-Atlantic coast region.

'Aguedilla' Strawberry

Aguedilla is a short-day strawberry (Fragaria ×ananassa Duch.) cultivar obtained by the Spanish public breeding program (Agreement CC01-0008-F1). 'Aguedilla' produces excellent extra-early, early, mid-season, and late-season large-sized, wedge-shaped fruit, and a low percentage of second quality fruit. An agronomic and sensorial characterization of this new cultivar, in comparison with the well-adapted cultivars 'Camarosa', 'Medina', and 'Ventana', was undertaken during the 2002–03 and 2003–04 crop seasons.

Pollen Quality and Performance in Strawberry Plants Exposed to High-temperature Stress

The effects of high-temperature stress on pollen viability and in vitro and in vivo germinability were studied in two facultative, short-day strawberries (Fragaria ×ananassa Duch.), `Nyoho' and `Toyonoka.' Plants were exposed to two day/night temperature regimes of either 23 °C/18 °C (control) or 30 °C/25 °C (high temperature) from when the first inflorescence became visible until anthesis. Pollen viability in `Nyoho' was only slightly affected at 30 °C/25 °C when compared with pollen from plants grown at 23 °C/18 °C. In `Toyonoka', however, pollen viability was significantly lower at 30 °C/25 °C than at 23 °C/18 °C. The in vitro germination percentages were significantly lower in pollen from plants grown at 30 °C/25 °C and germinated at 30 °C than from plants grown at 23 °C/18 °C and germinated at 23 °C in both cultivars. But the percentages were much lower in `Toyonoka' than in `Nyoho', particularly at the 30 °C germination temperature. Pollen from plants grown at 23 °C/18 °C also extended longer pollen tubes than pollen grown at 30 °C/25 °C in both cultivars, but `Nyoho' had longer pollen tubes than `Toyonoka' at 30 °C/25 °C. Fluorescence microscopy revealed that most of the `Nyoho' pollen germinated on the stamen, elongated through the style and reached the ovule regardless of temperature treatment. In `Toyonoka', pollen germination and elongation were greatly inhibited at 30 °C/25 °C, resulting in unfertilized ovules. These results suggest that certain strawberry cultivars produce heat-tolerant pollen, which in turn could result in higher fruit set.

Zinc Nutrition of Strawberries Grown on Peat Bags

Shortday strawberry plants (Fragaria xananassaDuch. ‘Elsanta’) were grown on peat bags. In a first trial, four rates of zinc (0.5, 5,10 and 15 μmol/liter) were applied in the nutrient solution. In ...

Identification of gibberellins in leaf exudates of strawberry (Fragaria ananassa Duch.).

Leaf exudates from the short-day (SD) strawberry (Fragaria × ananassa Duch.) cv. Elsanta were analysedfor gibberellin (GA) content using combined gaschromatography – mass spectrometry (GC-MS). Comparison of full-scan mass spectra and Kovatsretention indices (KRIs) with those of standardsrevealed the presence of GA1, GA3, 3-epiGA1 and GA3-isolactone.

Chloride Nutrition of Strawberries Grown on Peat Bags

Abstract Plants of the short-day strawberry (Fragaria × ana-nassa Duch. ‘Elsanta’) were grown on peat bags with four rates of chloride in the nutrient solution (0.5, 1.0, 1.5, and 2.0 mmol/1). Chloride application had no effect on pollen germination, fruit malformation, or fruit taste. Yield and fruit size were reduced at 2 mmol/liter Cl in the nutrient solution without plants showing any toxicity symptoms. The results indicate that the chloride concentration in the nutrient solution necessary for satisfactory growth and fruit quality of ‘Elsanta’ grown on peat bags appears to be very low.

Production of Short-Day Strawberries on Raised Beds in British Columbia

Abstract The commercial production of short-day strawberry (Fragaria × ananassa) varieties on raised beds was explored in two experiments. Our results indicate that there is no enhancement in winter injury when plastic soil mulches are used in place of no mulch. Conversely, no yield or fruit size advantage is gained by using plastic mulches in British Columbia. ‘Rainier’ grown on raised beds will provide a significant marketable yield in the planting year, with adequate yield in the subsequent year. This first-year return represents a significant advantage over ‘Totem,’ the dominant commercial variety at the present.

`Puget Reliance' Strawberry

‘Puget Reliance’ is a new short-day strawberry (Fragaria ×ananassa Duch.) cultivar jointly released by Washington State Univ., Oregon State Univ., Univ. of Idaho, and the U.S. Dept. of Agriculture–Agricultural Research Service (USDA–ARS). ‘Puget Reliance’ has been noted for high yields of large, medium-red conic fruit. ‘Puget Reliance’ appears to be very virus tolerant. ‘Puget Beauty’ is present five times in the pedigree of ‘Puget Reliance’. The name, ‘Puget Reliance’, was selected to reflect the contribution of ‘Puget Beauty’ in the pedigree and denote its adaptation to the Puget Sound region, its virus tolerance, and consistent high yields of large fruit.

Yield Components of Day-neutral and Short-day Strawberry Varieties on Raised Beds in British Columbia

Eight day-neutral and seven short-day strawberry (Fragaria ×ananassa, Duch.) varieties were evaluated on raised beds during 1990 and 1991 in the Fraser River valley, B.C. Among day-neutral varieties in 1990, total variation in marketable yield originated in fruit count (26%), total yield (18%), average leaf size (22%), and runner count (19%) per plant. In 1991, total variation in marketable yield originated in fruit count (38%), runner count (23%), crown count (13%), and total yield (16%) per plant. `Selva' was one of the most productive day-neutral varieties and had the heaviest fruit and the fewest culls during both years of the study. The short-day varieties had uniformly low yields of marketable fruit during the establishment year, 1990. Variation in marketable yield in 1991 originated in runner count (34%), total yield (18%), and fruit count (16%) per plant. Of the short-day varieties in 1991, `Shuswap' had the highest marketable yield and, along with `Pajaro' and `Sequoia', had the fewest culls. `Shuswap' was a prolific producer of runners, while `Sumas' and `Redcrest' yielded well without prolific runner production.

Glooscap and Blomidon strawberries

Glooscap and Blomidon are short-day strawberry (Fragaria × ananassa Duch.) cultivars which produce large fruit suited to the fresh market. Glooscap, which is particularly high yielding and winter hardy, ripens in midseason whereas Blomidon, which is particularly glossy and attractive, ripens mid- to late season. Key words: Fragaria × ananassa, fruit breeding, strawberry

The Contributions of Private Strawberry Breeders

The grand qualities of our present-day strawberries are traceable to three native octoploid American types obtained from the east coast of North America (Fragaria virginiana Duch.), the west coast of South America (F. chiloensis L.), and from the central California coast (F. chiloensis). The cross of the first two, made about 1750, was the progenitor of the current short-day strawberry. The hybrid strawberry thus obtained was named pine, short for pineapple, and also the ananassa strawberry, which, of course, also means pineapple (Fig. 1A). The flavor resembles pineapple (Darrow, 1966; Wilhelm and Sagen, 1972). About 125 years later, the California strawberry germplasm was introduced, first into Belgium, then France and England, and used in crosses with germplasm derived from the original cross. Hybrids resulting were progenitors of the ‘Perpetuel’, that is, the everbearing class of strawberry (Wilhelm, 1974). What makes strawberries unique among fruit crops, and especially interesting to those of us involved in the commercial breeding of strawberries, is their octoploid (8n) genetic composition, their recent interspecific (Fragaria spp.) hybrid origin, and the relatively short time between seed germination and fruiting. To meet present market standards, cultivars possess traits that have been pyramided, a term used by E. Goldsmith (Fig. 1E), over numerous seedling generations of selection and elimination. Worldwide, only a few private corporations are involved in strawberry breeding, but interest in private breeding ventures is growing. My own strawberry breeding efforts have been with Driscoll Strawberry Associates, Inc. (DSA), Watsonville, Calif. During the 34 years of my employment, upwards of 600,000 strawberry seedlings of hybrid origin have been raised, increased by runners, and fruited in blocks, often with replications in more than one location. The effort has resulted in 41 patented cultivars with unique qualities determined by DSA business policies. This work, all accomplished within a narrow parent base, has been recently turned over to T.M. Sjulin, formerly of Washington State Univ.