PLEASE SCROLL DOWN FOR ARTICLE

This article was downloaded by: [National Agricultural Library]On: 9 June 2010Access details: Access Details: [subscription number 919047039]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

International Journal of Fruit SciencePublication details, including instructions for authors and subscription information:http://www.informaworld.com/smpp/title~content=t792306963

Delaying Flowering in Short-Day Strawberry Transplants withPhotoselective NetsFumiomi Takedaa; D. M. Glenna; Ann Callahana; Janet Slovinb; Gary W. Stuttec

a Appalachian Fruit Research Station, USDA-ARS, Kearneysville, West Virginia, USA b GeneticImprovement of Fruits and Vegetables Laboratory, USDA-ARS, Beltsville, Maryland, USA c DynamacCorporation, Space Life Science Laboratory, Kennedy Space Center, Florida, USA

Online publication date: 08 June 2010

To cite this Article Takeda, Fumiomi , Glenn, D. M. , Callahan, Ann , Slovin, Janet and Stutte, Gary W.(2010) 'DelayingFlowering in Short-Day Strawberry Transplants with Photoselective Nets', International Journal of Fruit Science, 10: 2,134 — 142To link to this Article: DOI: 10.1080/15538362.2010.492331URL: http://dx.doi.org/10.1080/15538362.2010.492331

Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf

This article may be used for research, teaching and private study purposes. Any substantial orsystematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply ordistribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representation that the contentswill be complete or accurate or up to date. The accuracy of any instructions, formulae and drug dosesshould be independently verified with primary sources. The publisher shall not be liable for any loss,actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directlyor indirectly in connection with or arising out of the use of this material.

134

International Journal of Fruit Science, 10:134–142, 2010ISSN: 1553-8362 print/1553-8621 onlineDOI: 10.1080/15538362.2010.492331

WSFR1553-83621553-8621International Journal of Fruit Science, Vol. 10, No. 2, May 2010: pp. 0–0International Journal of Fruit Science

Delaying Flowering in Short-Day Strawberry Transplants with Photoselective Nets

Delaying Flowering in Strawberry TransplantsF. Takeda et al.

FUMIOMI TAKEDA1, D. M. GLENN1, ANN CALLAHAN1, JANET SLOVIN2, and GARY W. STUTTE3

1USDA-ARS, Appalachian Fruit Research Station, Kearneysville, West Virginia, USA

2USDA-ARS, Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville, Maryland, USA

3Dynamac Corporation, Space Life Science Laboratory, Kennedy Space Center, Florida, USA

Growing strawberry (Fragaria x ananassa Duch.) transplantsunder photoselective nets delayed flowering. In August, ‘Straw-berry Festival’ strawberry plug plants were grown under red orblue ChromatiNet® or without shading (control) in a glasshouse.Fall flowering response was determined following transplantinginto a plasticulture system in the field. The no-shade control plantsbegan flowering in late September and by late November, morethan 90% of the plants had bloomed. These plants produced fruitfrom October to early January. Flowering in plants that weregrown under red- or blue-colored shade net did not occur untilearly January. The results of this study suggested that the use ofphotoselective shade nets over strawberry plug plants in Augustblocks the light signal that initiates flowering until the netting isremoved, hence, delaying the initiation of flower buds until plantsare transplanted in the field.

KEYWORDS Fragaria, plug plant, flower, runner, shade fabric,solar radiation, light modification, light quality

This article is not subject to US copyright law.Address correspondence to Fumiomi Takeda, USDA-ARS, Appalachian Fruit Research

Station, 2217 Wiltshire Road, Kearneysville, WV 25401, USA. E-mail: fumi.takeda@ars.usda.gov

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

Delaying Flowering in Strawberry Transplants 135

INTRODUCTION

Control of flowering is important in strawberry (Fragaria × ananassaDuch.) production and the market requirement. In Florida, early blooms aredesired in order to sustain winter fruit production. In the mid-Atlantic coastregion, growers are motivated to produce fruit for the October–Decemberoff-season market window and to increase fruit production for a specialoccasion like Valentine’s Day, when there is good potential for high mone-tary returns (Takeda, 1999). Lacking an environment conducive to off-sea-son fruit production, such as the South Coast region of California,strawberry growers in the mid-Atlantic coast region are using plasticulture,high tunnels, day-neutral cultivars, and conditioned transplants to improveearly- and late-season strawberry yields (Takeda, 2008). Recently, Takedaand co-workers described an alternative method for promoting early flower-ing in SD cultivars (‘Chandler’, ‘Carmine’, and ‘Strawberry Festival’), whichdoes require exposure to cool temperatures or SD conditions to flower.More than 80% of transplants of these cultivars were induced to flower infall if runner tips were plugged into 50-cell trays in early July and main-tained in the greenhouse until late August (Takeda, 2008; Takeda and New-ell, 2006a, 2006b). In a subsequent study, Takeda et al. (2008) showed thatplacement of low-intensity red light emitting diode (LED) lamp (maximumwavelength at 662 nm) 1 cm from the crown of strawberry transplantssignificantly decreased the number of plants that flowered in the fall anddelayed flowering. This suggested that regulations of late season floweringthrough spectral quality could be achieved prior to transplanting.

Spectral filter films and nets with differential light scattering propertiesand altered proportions of R/FR ratio have been used as a nonchemicalmeans of growth control in horticultural crops (Fletcher et al., 2005; Shahak,2008). Normally shade nettings are used to mitigate temporary heat-inducedcessation in reproductive growth (Wagstaffe and Battey, 2008), but placingphotoselective greenhouse films over strawberry plug plants in September didnot significantly affect flowering time and resulted in reduced early and total-season yields than commercially produced transplants (Black et al., 2005).

Environmental manipulations are useful for delaying or suppressing thetime to flowering. Stock chrysanthemum plants were kept vegetative bylong-day, or with night breaks (Kofranek, 1980), and flowering in sugarcanes was suppressed during September to ensure that plants remainedjuvenile by night-break lighting when day lengths were conducive for floralbud induction (Moore, 1985). Also, flowering was delayed or inhibited byhigh temperatures on strawberries (Wagstaffe and Battey, 2008) and lowirradiance levels on rose shoots (Mor and Halevy, 1980). Light quality canbe manipulated with colored shade nets (e.g., ChromatiNet®, Polysack USA,Inc., San Diego, CA, USA) for promoting specific physiological responses inhorticultural crops (Shahak et al., 2004).

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

136 F. Takeda et al.

The objective of this study was to determine the subsequent growthand flowering response of strawberry plants in the field after transplantswere grown under photoselective nets for one month.

MATERIALS AND METHODS

On June 30, 2008, runner tips of the ‘Strawberry Festival’ strawberry (Chandleret al., 2000) purchased from a nursery (Lassen Canyon Nursery, Redding,CA, USA) were plugged into 50-cell pack trays (∼320 transplants·m−2) andmisted under intermittent sprinklers for 10 days to promote rooting in agreenhouse located at the Appalachian Fruit Research Station, Kearneysville,WV (lat. 39 °N). Afterwards, all trays were placed on a greenhouse benchand watered and fertilized as needed. On July 31, 2008, four trays of ‘Straw-berry Festival’ transplants were placed under a 1.2-m high, 2.2-m long, and1-mt wide frame erected on the greenhouse floor and on which two layersof colored, light-transmitting shade netting material (ChromatiNet® RedShade Net 30%, Polysack USA, Inc.) were draped. Four trays of ‘StrawberryFestival’ were placed under a second frame that was covered with two lay-ers of ChromatiNet Blue Shade Net 30%. The control plants were retainedon the bench unshaded. All trays were fertigated daily with 140 mg NO3·L

−1

H2O, which was drained after 30 min. On August 29, 2008, transplants wereestablished 30 cm apart atop raised beds at the University of Maryland WyeResearch and Education Center in Queenstown, MD (lat. 38.5 °N, USDAPlant Hardiness Zone 7a) after the methods described by Poling (1993). Ahigh tunnel (14.5 m long × 6.4 m wide, manufactured by Ledgewood FarmGreenhouse Frame, Moultonborough, NH, USA) was erected over the plantson October 17 and covered with a 4 mil infrared greenhouse film (TuffliteInfrared™, Covalence Plastics, Minneapolis, MN, USA). A hive of bumblebees (Koppert Biological Systems, Romulus, MI, USA) was placed in thetunnel in November for pollination. The plants were covered with a heavyrow cover whenever the temperature was expected to drop below 2°C.Plants with open flowers and fruit were counted at the end of September,October, and November 2008, and in early January 2009. Ripe fruit wereharvested at weekly intervals from September to December 2008 and fromMarch to May 2009. In summer 2009, the study was repeated, but the trans-plants were covered with only one layer of light-transmitting shade nettingmaterial (ChromatiNet® Red and Blue Shade Net 30%, Polysack USA, Inc.).The field experiments in both years were a randomized complete-blockexperimental design with four 8-plant replications. The raw flowering per-centage data were transformed using the arcsine-square root transformationbefore statistical analysis and subjected to an analysis of variance usingPROC GLIMMIX, which uses generalized linear models with a link functionto model the binary response where an individual plant either flowered or

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

Delaying Flowering in Strawberry Transplants 137

not at a given time (SAS Institute, Cary, NC, USA). This approach allowedmodeling of the repeated measures aspects of the study.

RESULTS AND DISCUSSION

Plants have evolved mechanisms to alter their growth and development inresponse to environmental signals. The transition from vegetative to repro-ductive development in strawberries is regulated by a number of environ-mental factors (Darrow, 1966). Conditioning treatments for plug plants,such as exposure to specific high and low temperatures (Bish et al., 2004)or low temperatures and short-day (SD) photoperiod (Durner, 1999; Heide,1977; Oda, 1989), have been described for hastening flowering in SD straw-berry transplants. In this study, three groups of ‘Strawberry Festival’ straw-berry transplants were subjected to the propagation scheme previouslydescribed (Takeda and Newell, 2006a; Takeda et al., 2008) that induces fallflowering. To block specific wavelengths (blue and green or green andred), two groups were placed under either blue- or red-colored shade netswhile a third group (control) was left unshaded.

In the unshaded control plants, flower buds started to emerge in Sep-tember 2008 (Table 1). By December, more than 90% of the control plantshad flowered. The control plants produced 141 g of fruit (15 g average fruitweight) between October and early January and 560 g per plant fromMarch 10 to May 14 (Fig. 1). Vegetative growth in the form of runner pro-duction averaged six runners per plant in September, decreasing to aboutthree in October then none after that. In contrast, the ‘Strawberry Festival’strawberry plants that were subjected to the same propagation scheme butwere under two layers of 30% blue- and red-colored shade nets in Augustdid not flower until January. The runnering resulted in an average of fiverunners per plant in September decreasing to four in October and then nomore in the following months. In spring, plants that were held under

TABLE 1 Effect of Growing ‘Strawberry Festival’ Strawberry Transplants in Cell Packs*

Runners (no./plant) Flowering plants (%)

Treatment Sept. Oct. Nov. Sept. 29 Oct. 28 Nov. 25 Jan. 5

Red 4.6 a 4.2 b 0 a 0 a 0 a 0 a 69 aBlue 5.0 a 3.7 a 0 a 0 a 0 a 0 a 53 aNo shade 5.9 b 2.7 a 0 a 47 b 80 b 91 b 100 b

*(300 Plants/m2) for one month under ambient light conditions or under two layers of red- and blue-colored shade nets, before planting in annual plasticulture system on August 28, 2008. Runners werecounted and removed at the end of September, October, and November in 2008. Plants with open flow-ers in each plot were recorded at about monthly intervals.Letters show significant differences within a column at P ≤ 0.05. Mean separation was performed usingarcsine transformation.

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

138 F. Takeda et al.

colored shade nets produced about 500 g per plant (Fig. 1). Growing trans-plants in August under only one layer of either blue or red Chromatinet col-ored net had less effect on fall flowering (Table 2).

Placement of transplants under colored shade nets in August delayedflowering until January, but had little or no effect on fall runnering in bothyears. Colored shade net treatments slightly decreased the amount of fruitproduced from March to May. These findings suggest that the plug trans-plants respond to environmental cues besides SD photoperiod and lowtemperatures to bring about flower induction and inflorescence differentia-tion in August when the day lengths are more than 15 hr long and temper-atures are above 22°C. Colored shade nets modify the spectrum andamount of light transmitted to the transplants (Shahak et al., 2004). Theability to vegetatively grow and produce stolons was not affected by shading

FIGURE 1 Effect of shade treatment in August on yield of ‘Strawberry Festival’ strawberryplants during fall 2008 and spring 2009 in high tunnel culture.

TABLE 2 Effect of Growing ‘Strawberry Festival’ Strawberry Transplants in Cell Packs*

Runners (no./plant) Flowering plants (%)

Treatment Oct. 2 Nov. 4 Total Oct. 2 Oct. 29 Nov. 18

Red 4.7 b 3.3 a 8.0 b 43 a 60 a 63 aBlue 4.6 b 3.1 a 7.7 ab 23 a 50 a 58 aNo shade 3.8 a 3.3 a 7.1 a 38 a 80 b 80 b

*(300 Plants/m2) for one month under ambient light conditions or under one layer of red- and blue-colored shade nets, before planting in annual plasticulture system on August 29, 2009. Runners werecounted and removed in October and November 2009. Plants with open flowers in each plot wererecorded in October and November.Letters show significant differences within a column at P ≤ 0.05. Mean separation was performed usingarcsine transformation.

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

Delaying Flowering in Strawberry Transplants 139

transplants in August. Also, the results of this and prior studies (Takeda andNewell, 2006b) indicated that flowering and fruit development does not havea deleterious effect on spring crop. Spring yields of plants that were summershaded and did not crop in fall were sometimes less than those plants thatwere unshaded in summer and fruited in fall (Fig. 1). In South Carolina, nei-ther marketable yield nor fruit sugar content was increased for ‘Sweet Charlie’strawberry in a forced fall/winter cropping system under ChromatiNets(Dufault and Ward, 2009a, 2009b). These authors concluded that lower ambi-ent light intensity from fall to spring overwhelmed any enhancement fromchanges in light quality provided by ChromatiNets. In Israel where light inten-sity is quite high in the winter, Shahak (2008) reported that the performanceof strawberries in annual plasticulture was improved by growing them underphotoselective nettings.

Durner et al. (1984) reported that flower bud formation in SD strawberriesoccur under a photoperiod >12 hr provided temperatures were below 16°C.In the mid-Atlantic coast region, flower bud initiation in SD cultivars occurs infall when the photoperiod shortens to 11–13 hr (Darrow, 1966; Waldo, 1930).About 16 to 21 days of short photoperiods are required for flower bud initiation(Guttridge, 1969; Sønsteby and Nes, 1998; Verheul et al., 2006), and plantsflower after 47 days from the end of the SD treatment. For strawberry plantsthat flowered around October 1 (Table 1), flower bud formation wouldhave occurred in mid August. The evocation that commits a bud to becomereproductive would have occurred even earlier. Covering transplants with twolayers of colored nets as described in this study prevented the further devel-opment of the flowers. Since all transplants had or were flowering by January,the new floral buds must have formed in plants treated with photoselectivecolored net once the plants were exposed to the natural short days in thefield. The results of the present study showed that, by maintaining plug plantsunder two layers of red and blue photoselective colored nets in August,flowering could be delayed until January. Growing the transplants underone layer of 30% red and blue ChromatiNet colored nets delayed floweringsomewhat (Table 2). These findings support a previous work that showed redlight (600–700 nm wavelengths), used for day-extension or night-break lightingand low irradiance during the floral inductive period inhibited or delayedthe early stages of flower bud differentiation in SD plants (Rees, 1987).

In strawberries, vegetative reproduction is the primary process used bynurseries for propagating plants. Strawberry plants multiply vegetatively viastolons (runners) that develop into daughter plants (Darrow, 1966). Flowerbuds are removed from mother plants in strawberry nurseries to preventflowering and fruiting stress on the plant and to promote runner produc-tion. Also, flowers and fruit are normally detached to reduce infection byColletotrichum species, the primary causal agent of strawberry anthracnosecrown and fruit rot. An occurrence of this disease in nursery beds mayresult in serious losses on fruit production farms where infected plants may

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

140 F. Takeda et al.

eventually die from vascular collapse or provide the inoculum to startflower and fruit infections the following spring (Sjulin, 2008).

The colored net treatment in August had little or no effect on runneringduring fall months in ‘Strawberry Festival’ strawberry plants. Both control plantand plants that were grown under red and blue photoselective nets producedabout seven to nine runners from September to November (Tables 1 and 2).This is significant to the strawberry transplant/nursery industry as a non-chemicalmeans for preventing or delaying blooms without affecting runner production.Early in the season, it is easy for workers to walk through the nurseries andremove the flowers and berries. Later in the summer when daughter plantsstart to root, tractor and human traffic must be limited to prevent damage tothe daughter plants and stolons. In these situations, tractors equipped withside booms to cover several rows with workers suspended over the strawberryplants in sling/harness or in sleeping bag-like contraptions are used for detach-ing flowers and fruit (Sjulin, 2008). Nursery flower removal operation is esti-mated to cost about $500 per acre (D. Marcum, University of CaliforniaCooperative Extension Service; personal communication). An alternative plantpropagation scheme for producing non-flowering stock plants may involve theestablishment of the stock plants in protected environments in late winter toproduce runners in the spring. Plug plants that are produced from these run-ner tips can be grown under a red- or blue-colored shade net for one monthbefore field establishment. Also, the technique described here for delayedflowering may also be useful for mid-winter fruit production or in a pro-grammed fruit production system in a protected environment to maximizeyield at special occasions like Valentine’s Day when the price for strawberries ishigh (Durner, 1999; Takeda, 1999). Additional studies are warranted to deter-mine whether these colored nets can prevent or delay bloom in day-neutralstrawberries and to better understand the relationship between levels of selec-tive light transmission and flowering response in short-day strawberries.

ACKNOWLEDGMENTS

The authors wish to thank Sharon Jones, Michael Newell, Frank Adams, andAnn Rose for their technical support.

LITERATURE CITED

Bish, E.B., D.J. Cantliffe, and C.K. Chandler. 2004. Strawberry transplant conditioningfor flowering induction. U.S. Patent 6,807,769. Oct. 26.

Black, B.L. H.J. Swartz, G.F. Deitzer, B. Butler, and C.K. Chandler. 2005. The effects ofconditioning strawberry plug plants under altered red/far-red light environments.HortScience 40:1263–1267.

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

Delaying Flowering in Strawberry Transplants 141

Chandler, C.K., D.E. Legard, D.D. Dunigan, T.E. Crocker, and C.A. Sims. 2000.‘Strawberry Festival’ strawberry. HortScience 35:1366–1367.

Darrow, G.M. 1966. The strawberry: The history, breeding, and physiology. Holt,Rinehart, and Winston, New York.

Dufault, R. and B. Ward. 2009a. Enhancing the productivity and fruit quality offorced ‘Sweet Charlie’ strawberries through manipulation of light quality inhigh tunnels. Intl. J. Fruit Sci. 9:176–184.

Dufault, R. and B. Ward. 2009b. Further attempts to enhance forced ‘Sweet Charlie’strawberry yield through manipulation of light quality in high tunnels. Int.J. Fruit Sci. 9:409–418.

Durner, E.F. 1999. Winter greenhouse strawberry production using conditionedplug plants. HortScience 34:615–616.

Durner, E.F., J.A. Barden, D.G. Himelrick, and E.B. Poling. 1984. Photoperiod andtemperature effects on flower and runner development in day-neutral, junebear-ing, and everbearing strawberries. J. Amer. Soc. Hort. Sci. 109:396–400.

Fletcher, J.M., A. Tatsiopoulou, M. Mpezamihigo, J.G. Carew, R.G.C. Henbest, andP. Battey. 2005. Far-red light filtering by plastic film, greenhouse-claddingmaterials: Effects on growth and flowering in petunia and impatiens. J. Hort.Sci. and Biotech. 80:303–306.

Guttridge, C.G. 1969. Fragaria. In: L.T. Evans (ed.). The induction of flowering.Macmillan Press, Melbourne, Australia.

Heide, O.M. 1977. Photoperiod and temperature interactions in growth and flower-ing of strawberry. Physiol. Plant. 40:21–26.

Kofranek, A. 1980. Cut chrysanthemums, p. 4–45. In: R.A. Larson (ed.). Introductionto floriculture. Academic Press, New York City, NY.

Moore, P.H. 1985. Saccharum, p. 243–262. In: Handbook of flowering, vol. 4. CRCPress, Boca Raton, FL.

Mor, Y. and A.H. Halevy. 1980. Promotion of sink activity of developing rose shootsby light. Plant Physiol. 66:990–995.

Oda, Y. 1989. Japanese strawberry industry—Trend of acreage, production, importand growing systems. Acta Hort. 265:671–678.

Poling, E.B. 1993. Strawberry plasticulture in North Carolina: II. Pre-plant, planting,and postplanting considerations for growing ‘Chandler’ strawberry on blackmulch. HortTechnology 3:383–393.

Rees, A.R. 1987. Environmental and genetic regulation of photoperiodism—Areview, p. 187–202. In: J.G. Atherton (ed.). Manipulation of flowering. Butter-worths, London.

Shahak, Y., E.E. Gussahovsky, E. Gal, and R. Ganelevin. 2004. ColorNets: Crop protec-tion and light-quality manipulation in one technology. Acta. Hort. 659:143–151.

Shahak, Y. 2008. Photo-selective netting for improved performance of horticulturalcrops. A review of ornamental and vegetable studies carried out in Israel. ActaHort. 770:161–168.

Sjulin, T.M. 2008. Special problems in nursery propagation of day-neutral straw-berry cultivars susceptible to Collectrichum acutatum. HortScience 43:78–80.

Sønsteby, A. and A. Nes. 1998. Short day and temperature effects on growth andflowering in strawberry (Fragaria × ananassa Duch.). J. Hort. Sci. Biot.73:730–736.

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010

142 F. Takeda et al.

Takeda, F. 1999. Out-of-season greenhouse strawberry production in soilless sub-strate. Adv. Strawberry Research 18:4–15.

Takeda, F. 2008. Recent innovations in cultural practices in the mid-Atlantic coastregion of the United States: Novel system for increasing fall fruiting in short-day type strawberry cultivars and out-of-season fruit production, p. 32–37. In:F. Takeda, D. Handley, and B. Poling (Eds.). Proceedings of the 2007 NorthAmerican Strawberry Symposium, Kemptville, Ontario, Canada.

Takeda, F., and M. Newell. 2006a. A method for increasing fall flowering in short-day ‘Carmine’ strawberry. HortScience 41:480–481.

Takeda, F., and M. Newell. 2006b. Effects of runner tip size and plugging date onfall flowering in short-day strawberry (Fragaria × ananassa Duch.) cultivars.Int. J. Fruit Sci. 6:103–117.

Takeda, F., D.M. Glenn, and G.W. Stutte. 2008. Red light affects flowering underlong days in a short-day strawberry cultivar. HortScience 43:2245–2247.

Verheul, M.J., A. Sonsteby, and S.O. Grimstad. 2006. Interactions of photoperiod,temperature, duration of short-day treatment and plant age on flowering onFragaria × ananassa Duch. cv. Korona. Scientia Hort. 107:164–170.

Wagstaffe, A. and N.H. Battey. 2008. Tunnel production of strawberry in the UK: Areview, p. 23–28. In: F. Takeda, D. Handley, and B. Poling (Eds.). Proceedingsof the 2007 North American Strawberry Symposium, Kemptville, Ontario,Canada.

Waldo, G.F. 1930. Fruit-bud formation in everbearing strawberries. J. Agr. Res.40:409–416.

Downloaded By: [National Agricultural Library] At: 11:40 9 June 2010