Varied a Des, Fotos, Comision Californiana

7/31/2019 Varied a Des, Fotos, Comision Californiana

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California Strawberry Commission 2008-09 Annual Pomology Project Report

Project Title: Strawberry genetics, breeding, physiology and production management

Principal Investigators:Kirk D. Larson, Pomologist and Strawberry Specialist, Dept. of Plant Sciences, UC Davis

(located at U.C. South Coast R.E.C., Irvine, California)

Douglas V. Shaw, Professor and Geneticist, Dept. of Plant Sciences, U.C. Davis

Co-InvestigatorsThomas R. Gordon, Professor, Dept. of Plant Pathology, U.C. DavisFrank G. Zalom, Entomologist, Dept. of Entomology, U.C. DavisSteve Koike, Extension Plant Pathologist, Univ. of Calif. Coop. Extension, Monterey County, CA

Please note: The intent of the Principal Investigators is to deliver an annual web-based report to the California strawberryindustry by September 15 of each year in which we receive funding from the California Strawberry Commission. In 2009we did not meet our September 15 publication deadline as the CSC did not release research funds to our project untiafter November 20 of 2009.

AbstractDuring the 2008-09 reporting period, we conducted investigations throughout the state to developstrawberry germplasm with improved production efficiency, environmental and disease tolerance, andimproved product quality and market acceptance. The short-day cultivar Palomar was released in the2006-07 production season and three day-neutral cultivars, Monterey, Portola and San Andreaswere released during the 2007-08 production season. We continue to conduct research on these newcultivars with the goal of defining appropriate production management practices.

In regard to cultivar improvement, breeding and selection activities in Davis/Watsonville and in Irvineare focused on the development of germplasm adapted to the Central Coast region (Santa Marianorth) and South Coast region (Santa Maria south), respectively. Additional breeding activities haveincluded on-farm evaluations of advanced selections in grower-cooperator fields around the stateThese on-farm trials typically involved 100-1,000 plant plots for each of 5-10 items. In these state-wide trials, much of our effort has been placed on assessing the yield performance of severapromising advanced short-day selections that have potential to be cultivars.

Efforts to develop germplasm with outstanding horticultural traits and resistance/tolerance toVerticillium dahliae, Phytophthora cactorum and Colletotrichum acutatum have continued, and in2009 we initiated work to develop genetic screens for Fusarium oxysporum and Macrophominaphaseolina at UC Davis and South Coast REC, respectively. Through use of repeated geneticscreens during the past 12 years, we have identified good sources of disease resistance toPhytophthoraand Verticilliumwithin the UC breeding program. By means of recurrent breeding andselection, these traits are continually incorporated into selections that possess the requisitehorticultural traits required of commercial cultivars. During the past seven years, we have worked todevelop a genetic screen for identifying sources of resistance to C. acutatum. We have observeddifferences in resistance to C. acutatum among the various genotypes tested, as well differencesamong genotypes in regard to resistance of fruit and plant to infection: in some genotypes the fruit ishighly susceptible but the plant is not, and vice versa.

Additional activities during this period have focused on the effectiveness of novel soil fumigants anduse of tunnels for solarization, as well as determining the influence of various irrigation and fertilitymanagement practices during the early fall plantation establishment period in southern California.


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IntroductionImprovement in the efficiency and product quality of strawberry production systems results from thedevelopment of superior production environments and breeding of cultivars specifically adapted to theseenvironments. Research at the University of California in strawberry plant breeding and productionphysiology has resulted in cultivars and cultural practices that are responsible for the states position asthe worlds largest strawberry producer. The competitive position currently held by California strawberrygrowers can be traced to use of cultivars that have broad environmental adaptation, innovative

production systems that maximize yield, fruit quality, and harvest efficiency, and use of pest andpathogen-free plants and soil environments. However, agricultural markets and production environmentsare not static: currently, the California strawberry industry faces challenges due to an increasinglycompetitive market, rising production costs and decreasing fruit prices (in constant dollars), and thelikelihood that a highly effective production tool, methyl bromide, will be unavailable in the near future.

California strawberry growers need to overcome market and production cost barriers while experiencingincreased costs and a decrease in the quality of the production environment. Our primary researchobjectives are to develop breeding and cultural solutions to these problems, and our activities to addressthese research objectives are summarized below.

Summary: The central focus of the U.C. Davis strawberry (Pomology) program is the release ofimproved cultivars and development of cultural methods for optimizing their performance. In addition,we are focused on long-term breeding efforts with the goal of developing superior cultivars with broadenvironmental adaptation and disease tolerance. We continue to investigate the benefits andlimitations of fumigation alternatives and other technologies that have potential for increasing yield,fruit quality and production efficiency. A summary of the most important activities is included below.

Performance of newly-released cultivars Palomar, Monterey, Portola and San AndreasThe short-day cultivar Palomar was released in spring of 2007 (Fig. 1). Plants of Palomar are compactwith relatively low vigor, but with appropriate treatments are capable of producing 1000 crates/acre o

fruit in southern California by mid-January (Table 1). To sustain such early-season fruit loads, Palomargrowers must use early digging/planting dates, bed mulches that warm the soil (Table 2) andappropriate, site-specific irrigation and fertility management practices. Presently, use of the Palomarcultivar is confined to southern California, and acreage has doubled (to >600 acres) since the 2008-09season.

Due to a low cull rate, compact growth habit, early fruiting, excellent pollination, uniformly-shapedberries, and a tendency to produce fruit on long peduncles (stems) (Fig. 3), Palomar has exceptionaharvest efficiency. Early season yield of Palomar can be quite high (Table 3) regardless of plant spacingHowever, Palomars compact plant size enables growers to use 15-20% more plants per acre (~28,000-29,000 plants vs. 24,500 plants/acre for Ventana), resulting in increased early and total yields.

Fruit of Palomar has excellent appearance, with very good internal and external color and firmness(Figs. 4, 5). Subjectively, fruit flavor of Palomar is consistently ranked as either excellent or very goodWith excellent internal and external fruit color, Brix, shape and firmness, Palomar fruit should be anexcellent processing berry (Fig. 6).

A major caution with Palomar is that early season fruit often develops a dry calyx which detracts from theoverall appearance of the fruit (Figs. 7, 8). Research conducted in Florida and Spain suggests that highnutrient levels (high soil Ec) in combination with cold temperatures can exacerbate this problem, butconclusive evidence has not been presented at this time. Another caution is that Palomar is susceptibleto Phytophthoraroot and crown rot (Fig. 9), and growers should use appropriate preventative measures.


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Fig. 1. Fruiting plants of Palomar in April in Watsonville, California.

Fig. 2. Fruiting plants of Palomar in early December in Irvine, California.


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Fig. 3. Fruiting plants of Palomar in early April in Irvine, California.

Note compact plant, uniform fruit shape/size and easily-harvested fruit.

Fig. 4. Palomar fruit in tray.


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Fig. 5. Fruit of Palomar in February in Irvine, California. Note internal color and small cavity.

Fig. 6. Fruiting plants of Palomar in June in Irvine, California.

Note uniform size and shape of fruit, and open, erect plant canopy that facilitates harvest.


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Figs. 7, 8. Dry calyx in green and mature fruit of Palomar. Oxnard, Calif. Jan., 2005.

Fig. 9. Palomar plant collapse caused by Phytophthora cactorum.


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Table 1. Performance of Palomar planted with clear and black polyethylenemulch on two dates at the U.C. South Coast R.E.C., Irvine, California, 2007-08.

Yield (12# Crates/Acre) todig / plant date Mulch March 1 April 1 June 1

Sept. 27 / Oct.1 Black 1184 2426 7052

Clear 1629 3087 7592

Oct. 4 / Oct. 8 Black 918 1764 6570

Clear 1148 2331 6935

Macdoel plants, 24,500 plants/acre on 4-row bed.

Table 2. Early-season yield performance (to January 13, 2007*) ofPalomar and Ventana at the U.C. South Coast R.E.C., Irvine, California, 2007.

FruitNo. of 12# Size Appearance Firmness

Item Crates/Acre (g) (5=best) (5=v. firm)

Ventana 558 36.1 3.6 3.7

Palomar 977 34.2 4.0 4.0

Macdoel plants, 24,500 plants/acre on 4-row bed.* Freeze event with temperatures of 26 F on Jan 13, 2007.

Table 3. Performance of fresh-market Palomar andVentana on clear polyethylene mulch in Oxnard*, 2008-09.

Yield (12# Crates/Acre) toItem March 1 May 16

Palomar 1,217 5,701

Ventana 1,199 5,337

*Macdoel plants planted Oct. 1

Data courtesy of Glen Hasegawa and Steve ImotoCamarillo Ranch, Ventura Co., California


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The new day-neutral cultivars Monterey, Portola and San Andreas were released to the Californiaindustry in spring of 2007. All three cultivars produce significantly greater yields than Albion.

Monterey is a moderate day-neutral, slightly stronger flowering than Albion with a similar productionpattern in Watsonville, but with a later peak in southern California. More than five million plants ofMonterey have been planted in Oxnard for fruit production in 2009-10. In southern California, plantsof Monterey are vigorous and require spacing similar to that of Ventana (Figs. 10-12). Fruit ofMonterey is larger but less firm than that of Albion, although post harvest traits for Monterey are

similar to those of Albion. Monterey has outstanding flavor with a very sweet aftertaste that is uniqueamong California cultivars. Anecdotal evidence suggests that Asian consumers are especiallyinterested in Monterey. Monterey has good disease resistance, although it is susceptible to powderymildew (Sphaerotheca macularis) and anthracnose (Colletotrichum acutatum). Control of powderymildew in this cultivar will require attention by both nursery and fruit growers. Monterey is an excellentnursery runner producer.

Portola is a strong day-neutral cultivar with broad adaptation. This cultivar can be used in standardwinter planting systems, and it is earlier than Albion to initiate fruiting. Due to a strong floweringresponse Portola is well adapted to spring and summer planting systems in Santa Maria and Oxnardand typically produces >4000 crates/acre. Portola has a vigorous plant and will require a lower plant

density than Albion (Figs. 13-14). Fruit of Portola is similar in size to Albion but lighter in color andwith more shine (Figs. 15-17). Post harvest characteristics for Portola are similar to those for Albionbut Portola is less rain tolerant than most UC cultivars. Fruit flavor for Portola is excellent andconsistent throughout the fruiting season. Cold-stored plants of summer-planted Portola are vigorousand large in size, and resistant to Phytophthora cactorumbut moderately susceptible to Verticilliumdahliaeand Colletotrichum acutatum. Leaves and fruit are moderately susceptible to powdery mildew(Sphaerotheca macularis). Nursery productivity for Portola is exceptional.

San Andreas is a moderate day-neutral cultivar. In the Central Coast region, San Andreas has aproduction pattern similar to that of Albion, but in Southern California it is earlier to fruit than Albion. InWatsonville, plant vigor for San Andreas is somewhat greater than for Albion early in the season bu

plant size throughout the fruiting season is similar to Albion due to its high and consistent productivity(Figs 18, 19). In southern California, San Andreas is not a highly vigorous plant and has extremelyhigh harvest efficiency. As with the cultivar Palomar, growers should consider use of clear or Pandabed mulch and higher plant densities compared to Ventana or Camarosa. This cultivar produces fewrunners in the fruiting field.

Fruit of San Andreas is exceptional in appearance (Figs. 20-22) and notably superior to Albion earlyin the season. San Andreas fruit color is slightly lighter than that of Albion, and has similar postharvest characteristics and exceptional rain tolerance. The flavor of San Andreas is very good andsimilar to that of Albion. San Andreas has a good disease resistance profile with no outstandingcautions. Due to a low chilling requirement, early production and excellent fruit quality, San Andreas

has quickly become a major commercial cultivar in southern California production districts. Nurseryproductivity for San Andreas is similar to or slightly below that for Albion.

Fertility management of Albion and San Andreas cultivars in Southern California. There isconsiderable acreage of the day-neutral cultivars Albion and San Andreas in Southern California, andthese cultivars perform best with early nursery digging and immediate planting (no cold storage) inlate September. Early-dug plants of these cultivars are not highly vigorous, but vegetative growth isenhanced with clear polyethylene bed mulch and nitrogen applications. Occasionally, the first flowerpanicle may need to be removed to encourage vegetative plant development in these cultivars .


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Fig. 10. Fruiting plants of Monterey in April in Santa Maria, California.

Fig. 11. Fruiting plants of Monterey in May in Watsonville, California.


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Fig. 12. Fruiting plants of Monterey in June in Irvine, California.

Fig. 13. Fruiting plants of Portola in May in Santa Maria, California.


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Fig. 14. Fruiting plants of Portola in April in Watsonville, California.

Fig.15. Fruit of fall-planted, high-elevation plants of Portola in July in Watsonville, California.


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Fig. 16. Fruit of summer-planted Portola in November in Irvine, California

Fig. 17. Fruit of summer-planted Portola in November in Irvine, California.


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Fig. 18. Fruiting plants of San Andreas in April in Santa Maria, California.

Fig. 19. Fruiting plants of San Andreas in May in Watsonville, California.


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. Fig. 20. Fruiting plants of San Andreas Fig. 21. Fruit of San Andreas in January in Oxnard, California.

in November in Irvine, California.

Fig. 22. Fruit of San Andreas in November in Irvine, California.


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Results for Watsonville performance trials for the new day-neutral cultivars compared with Diamanteand Albion are shown in Table 3. All three new day neutral cultivars have about 20% greater totalyield as well as greater late-season yields compared to Albion and Diamante. Results of performancetrials for fall plantings in the Central Coast region indicate that there is relatively little difference inyield or fruit quality for high elevation plants stored for 2.5 or 3.5 weeks, suggesting that thesecultivars are relatively stable to differing nursery treatments (Table 4). Plants of Monterey and SanAndreas have somewhat reduced yields with later plantings, so very late nursery harvest and longperiods of cold storage should be avoided for these cultivars. In southern California, the new day-

neutral cultivars perform best with late-September digging dates and immediate planting with nosupplemental cold storage (Tables 5, 6).

Table 3. Average Performance of Three New Day Neutral Cultivars Compared with Albion andDiamante at the Watsonville U.C. Strawberry Research Facility, 2005-08

Late Appearance FruitYield Yield Score Size Firmness

Item (C/A) (C/A) (5 = best) (g/fruit) (lbs/inch2)

Albion 8,433 2,170 3.6 32.1 11.0Diamante 8,167 2,246 3.9 31.6 11.1Monterey 10,396 2,590 3.5 33.0 10.8Portola 10,270 2,702 4.4 31.9 11.6San Andreas 10,884 2,730 3.6 32.7 10.3

Macdoel plants harvested October 15 and planted with 2.5 weeks of cold storage.

52-inch beds with 17,300 plants per acre.

Table 4. Average Performance of Three New Day Neutral Cultivars Planted with Varying ColdStorage Treatments at the Watsonville U.C. Strawberry Research Facility, 2005-08

Late Appearance FruitWeeks Yield Yield Score Size

Item Storage (C/A) (C/A) (5 = best) (g/fruit)

Monterey 1 10,390 2,694 3.5 32.32.5 10,396 2,170 3.5 33.03.5 9,726 2,356 3.3 31.6

Portola 1 9,504 2,509 4.3 31.42.5 10,270 2,702 4.4 31.93.5 10,120 2,708 4.5 32.1

San Andreas 1 10,364 2,669 3.7 31.52.5 10,884 2,730 3.6 32.73.5 11,028 2,822 3.6 31.8

Macdoel plants harvested October 15 and planted after 1 to 3.5 weeks of cold storage.

52-inch beds with 17,300 plants per acre.


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Breeding cultivars with disease resistance and outstanding horticultural characteristics

During the past 13 years, our project has invested significant resources in developing genetic screensfor the soilborne pathogens Verticillium dahliaeand Phytophthora cactorumas well as fortwo-spottedmite and powdery mildew. In 2003 we initiated work to develop a genetic screen for Colletotrichumacutatum, and in 2009 we initiated work to develop genetic screens for Fusarium oxysporuumandMacrophomina phaseolina. Work with Verticillium, Phytophthoraand Fusariumhas been conduced atthe U.C. Wolfskill Experimental Orchard near Davis, while work with Colletotorichum andMacrophomina has been conducted at the U.C. South Coast R.E.C. in Irvine. Our objective in

conducting this research is two-fold: 1) to identify disease resistance/susceptibility profiles forpotential cultivars and advanced selections; and 2) to develop breeding populations that haveoutstanding horticultural traits andgood disease resistance/tolerance.

Our genetic screen methodologies are derived from Kochs postulates in that 1) the causalmicroorganism is isolated from a diseased plant and then grown in pure culture; and 2) themicroorganism causes disease when introduced into healthy plant tissues. To avoid confoundingresults in conducting our genetic screens, we apply methyl bromide/chloropicrin as a pre-plant soifumigant to eliminate all soilborne pathogens from our disease screening sites and we inoculate witha single pathogen. For the same reason, we use only disease-free planting stock obtained from ourcarefully maintained nurseries and propagation facilities. Depending on the disease, we inoculate

either soil or healthy plants with the pathogen of interest and then compare growth, survival and/oryield of the inoculated plants with non-inoculated controls. To date we have made significant progressin developing cultivars that have outstanding horticultural characteristics as well as improved diseaseresistance profiles.

Our Colletotrichum acutatumgenetic screen relies on the use of plug plants that are propagated in adisease-free environment. Each year, runner tips of about 50 cultivars and advanced selections areselected for uniformity and propagated under intermittent mist to make plug plants (Figs. 23-25). Plugplants of each genotype are either inoculated with spores of C. acutatum(Fig. 26) or maintained asnon-inoculated controls. Inoculated plants are watered frequently for 7-10 days to encourage infection(Fig. 27) after which the control and inoculated plants are established in the field (Fig. 28). Advanced

selections that are tolerant and intolerant of C. acutatum are shown in Fig. 29 and Fig. 30respectively.

Fig. 23. Runner tip development. Fig. 24. Selection and propagation Fig. 25. Rooted plug plant.of runner tips.


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Fig. 26. Preparation of C. acutatuminocula used to infect Fig. 27. Inoculated plug plants are sprinkled frequently

experimental plug plants. to encourage disease infection

Fig. 28. Colletotrichum genetic screen evaluation field withinoculated and non-inoculated plants

Fig. 29. Advanced selection in our genetic screen Fig. 30. Advanced selection in our genetic screenthat is relatively tolerant to C.acutatum. that is relatively intolerant to C. acutaum.

Non-inoculatedcontrol plants

Plants inoculatedwith C. acutatum

Non-inoculatedcontrol plants

Plants inoculatedwith C. acutatum


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Disease resistance scores for objective trials are presented in Table 5 for new and current cultivars.All of the new day neutral cultivars are at least moderately resistant to Verticillium wilt andPhytophthoracrown rot, but Palomar is fairly susceptible to Phytophthora. Portola and Monterey aremoderately susceptible to plant infection by Colletotrichum, but none of the new cultivars areespecially sensitive to fruit infection with this pathogen. The most important caution is that Montereyis susceptible to powdery mildew, and this pathogen will require close control for this genotype. None

of the selections show excessive susceptibility to spidermites, although anecdotal evidence suggeststhat in southern California early-planted San Andreas and Palomar may be somewhat moresusceptible to two-spotted mites than other U.C. cultivars.

Table 5. Disease resistance scores for standard and new U.C. cultivars

Phytophthora Verticillium Colletotrichum

Item cactorum dahliae acutatum

Camarosa 3.6 2.5 2.6

Camino Real 4.4 4.2 3.1

Ventana 2.5 3.0 3.0

Albion 4.3 3.8 3.4

Palomar 2.4 3.3 3.2

Monterey 3.2 3.4 2.4

Portola 3.8 3.8 2.9

San Andreas 4.4 3.3 2.7

Resistance scores: 1 = highly susceptible, 5 = highly resistant

Breeding Objectives and Development of New Short-Day CultivarsOur program seeks to develop short-day cultivars that have early production with a long fruiting season,

with little or no gaps, and an attenuated mid-season peak. Plants should be easy to grow in bothnurseries and fruiting fields, with an architecture that facilitates harvest efficiency, and fruit should haveconsistently good flavor and quality. We actively seek to develop plants and fruit that have goodenvironmental and disease tolerance.

Nine new, distinct short-day cultivars were evaluated at UC research facilities and in grower trials aroundthe state in 2008-09, and two of these selections, C225 (Fig. 31) and C227 (Fig. 32), are in the processof cultivar disclosure.


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Fig. 31. Fruiting plants of advanced short-day selection C225 at the So. Coast REC, Irvine, California.

Fig 32. Fruiting plants of advanced short-day selection C227 at the So. Coast REC, Irvine, California.

In statewide trials, both C225 and C227 have similar production patterns to Ventana and comparableearly-season and total-season yields, but with lower cull rates, greater harvest efficiency, larger fruit size,and greater fruit quality, including flavor (Tables 6, 7 and 8).


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Table 6. Three-year* Average Yield Performance for High-elevation Advanced Short-day SelectionsC225 and C227 Compared with Ventana and Camarosa in Irvine, California.

Dug Sept 26 / planted Sept 30 Fruit .

12# C/Acre to 3/1 Cull 12# C/Acre to 6/8 Cull Size App. Firm.

Item Total Marketable % Total Marketable % (g) (5=best) (5=firm)

C225 1,782 1,701 4.6 10,022 8,060 21.6 34.4 3.1 3.4

C227 2,282 2,120 6.0 9,792 8,496 13.2 36.6 3.8 3.2

Ventana 1,832 1,553 15.2 8,829 6,930 21.5 32.5 3.2 3.4

Camarosa 1,494 1,211 19.0 9,189 6,903 24.9 31.0 2.6 3.4

* Table shows only one year of performance data for C225 for this planting dateMacdoel plants with 24,500 plants/acre on a 64-inch wide 4-row bed

Table 7. Three-year* Average Yield Performance for High-elevation Advanced Short-day SelectionsC225 and C227 Compared with Ventana and Camarosa in Irvine, California.

Dug Oct 3 / planted Oct 6 Fruit .

12# C/Acre to 3/1 Cull 12# C/Acre to 6/8 Cull Size App. Firm.

Item Total Marketable % Total Marketable % (g) (5=best) (5=firm)

C225 1,053 995 5.6 8,028 6,579 18.1 33.3 3.4 3.5

C227 1,166 1,098 5.8 8,114 7,065 12.9 35.8 3.7 3.3

Ventana 1,229 1,103 10.3 8,352 6,368 23.8 32.1 3.4 3.4

Camarosa 734 536 27.0 8,136 5,819 28.5 30.9 2.7 3.4

* Table shows only two years of performance data for C225 for this planting dateMacdoel plants with 24,500 plants/acre on a 64-inch wide 4-row bed

As in past years, test plots of the short-day selections C225 and C227 have been established in variousgrower-cooperator fields throughout the state in the 2009-10 season. Several cooperators establishedC225 and C227 in day-neutral plantings of Albion and San Andreas rather than in plantings of short-dayvarieties such as Ventana. Plants of C225 and C227 are fairly vigorous, and it appears that the nitrogenfertility management program used for the day-neutral cultivars has resulted in excessive vigor and areduction in fruiting in C225 and C227. Growers should always consider the effects of nitrogen fertilitymanagement when planting more than one cultivar in a given field.


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Table 8. Performance of Ventana, C225 and C277 Evaluated at South Coast R.E.C. - Irvine,

Santa Maria and the Watsonville Strawberry Research Facility in 2008 and 2009

FruitEarly Cull AppearanceYield* Yield Rate Score Size Firmness

Location Item (C/A) (C/A) (%) (5=best) (g) (5 = v. firm)

Irvine Ventana 1,168 6,714 21.7 3.3 33.6 3.3

(Oct. 3-5) C225 992 6,577 17.8 3.4 33.3 3.5

C227 1,098 6,797 13.7 3.7 34.8 3.3

Sta Maria** Ventana 532 4,975 33.3 - 27.2 -

(Oct. 23-26) C225 602 5,895 26.4 - 29.5 -

C227 493 4,009 26.7 - 30.8 -

Watsonville Ventana 3,051 8,274 - 3.0 33.3 9.8

(Oct. 23-26) C225 2,975 8,175 - 3.6 33.7 10.0

C227 2,154 7,183 - 3.7 36.0 9.3

* Early yield calculated to March 1, April 10, and May 1 for Irvine, Sta. Maria, & Watsonville respectively.

** 2008 results only.

Both of the new advanced selections are well-adapted to early planting in southern California productionsystems. Plants of C225 are moderately vigorous but more open than Camarosa (Fig. 31), and fruit issimilar in shape and color to Camarosa but larger in size and with consistently excellent flavor (Figs. 3334). Plants of C227 have moderate vigor and an open plant canopy (Fig. 32), and fruit is larger than thatof Camarosa with better flavor, a consistent conical shape and a bright red shine (Figs. 35, 38). Fruit oC227 maintains a large fruit size throughout the season, and while its fruit is somewhat softer than mostUC cultivars, it is firmer than many commercial cultivars grown in California.

A qualitative summary of performance characteristics and postharvest traits (Table 9) demonstratesthat the two advanced short-day selections are superior to Ventana for most individual characteristics.Subjectively, fruit of both of these advanced selections have flavor superior to that of Ventana, andwith similar rain tolerance.

The advanced selection C225 has good tolerance to Phytophthora cactorum but is susceptible toVerticillium, while C227 has good tolerance to Verticilliumbut is susceptible to Phytophthora(Table 10)Both items are intermediate in susceptibility to Colletotrichum. Neither item appears to be especiallysusceptible to powdery mildew (Sphaerotheca macularis) or 2-spotted mites. Nursery productivity forboth items is good and better than Ventana.


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Fig. 33. Fruit of advanced short-day selection C225. Fig. 34. Cross-sectional view of fruit of C225.

Fig. 35. Fruit of advanced short-day selection C227. Fig. 36. Cross-sectional view of fruit of C227.


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Table 9. Qualitative Evaluations for Two New Short-Day Advanced Selections Compared to Ventana.

C225 Compared C227 ComparedTrait with Ventana with Ventana

Productivity 0 0Production pattern 0 +

Fruit size + +

Firmness + 0

Appearance + +

Flavor + +

Postharvest storage + 0

Rain/Weather tolerance + +

Disease tolerance 0 0

Mite tolerance 0 0

Harvest ease + +

Cull rate + +

Runners (nursery) + +

Table 10. Disease resistance scores for Ventana, C225 and C227 in 2008 and 2009.

Phytophthora Verticillium Colletotrichum*

resistance resistance resistance

Genotype score score score

Ventana 2.1 2.9 2.7

C225 3.5 2.1 2.6

C227 2.3 3.8 2.7

Resistance scores: 1 = highly susceptible, 5 = highly resistant

*evaluated in 2009 only.


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Strawberry Production System Management Research

Irrigation Method and Fertility Management Affect Plantation Establishment. A three-yeardrought in California has resulted in reduced irrigation water quality and availability in many parts ofthe state. Several irrigation districts in strawberry growing regions have indicated that, due to waterscarcity, future water deliveries may be reduced during the fall strawberry planting season. Alsosome irrigation districts have converted (or will be converting) to the use of reclaimed water, whichhas higher salinity levels than normal irrigation water. The spike in energy prices in 2008-9 resulted

in greatly inflated prices for fertilizer and plastic, prompting some growers to use soluble pre-plantfertilizers rather than standard controlled-release (CR) fertilizers like Agriform (Scotts SierraMarysville, OH). Here, the concern is that use of soluble fertilizers could exacerbate soil and watersalinity levels and cause damage to bare-root strawberry transplants (Figs. 37, 39).

We established a 0.2-acre field trial at the U.C. South Coast R.E.C. in Irvine, California in 2008-09 todetermine effects of irrigation method (drip vs sprinkler), fertility management (CR vs. CR + solublefertilizer) and mulch (clear vs. black) on plant establishment and survival.

In early September, 2008 we used a half-acre plot of fumigated ground (350 #/acre of 57:43 methybromide : chloropicrin) to make four-row beds on 64-inch centers. Beds had two drip lines, and wereformed using either of two fertilizer treatments applied in a slot directly under the plotting rows at a

4.5-inch depth: 1) CR Agriform 18-8-13 at a rate of 200# of nitrogen/acre; or 2) a mixture of CRAgriform 18-8-13 at a rate of 100 pounds of nitrogen/acre and 15-15-15 at a rate of 100 pounds ofnitrogen per acre. Three beds of each fertilizer treatment (six beds total) were located near one edgeof the field and received only drip irrigation while six identical beds were located at the other edge ofthe field and were irrigated with sprinklers and occasional drip-irrigation. Black and clear polyethylenemulches were applied equally to both irrigation treatment blocks. Irrigation treatments were treated asmain plots while fertilizer and mulch treatments were randomized within main plots and considered asminor plots.

Bare-root, high-elevation plants of Camarosa, Palomar, San Andreas and Ventana were establishedon October 6, 2008 in the various treatment plots. The October-November establishment period was

characterized by well-above normal temperatures and frequent, strong Santa Ana winds. For thesprinkler treatment, irrigation was applied daily or even more frequently depending on temperatureand wind conditions. In contrast, was not possible to drip-irrigate the drip-only plots more than onceper day as even one daily drip-irrigation cycle often resulted in bed collapse due to soil saturation.Despite daily drip-irrigation, salinity build-up at the base of plants receiving drip-only irrigation resultedin severe plant stunting (Fig. 38-40), particularly in the CR + 15-15-15 fertilizer treatment. In the drip-only plot, use of CR fertilizer resulted in 4.5% plant mortality, while use of CR + 15-15-15 fertilizersresulted in a 24.4% mortality rate (Table 11). In contrast, plants receiving sprinkler-irrigation sustainedeither zero mortality or a 0.15% mortality rate when established with CR fertilizer or CR + 15-15-15fertilizer, respectively.

We continue to study the effects of various irrigation methods and fertility management programs onplant establishment and yield during the 2009-10 season.


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Fig. 37. Soil salinity concerns in drip-only irrigated strawberry fields.

Fig. 38. Salt accumulation at base of drip-only irrigated plant.


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Fig. 39. Bare-root Ventana plants established with drip irrigation only.

Fig. 40. Bare-root Ventana plants established with sprinkler irrigation.


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Table 11. Irrigation, fertility management and bare-root transplant mortality, Irvine 2008-09.

Irrigation Fertilizer % Planttreatment treatment mortality

Drip-only CR (18-8-13)* 4.5

CR (18-8-13) 24.4

+ 15-15-15 **

Sprinkler CR (18-8-13)* 0+ drip

CR (18-8-13) 0.15

+ 15-15-15 **

* CR 18-8-13 = Scotts Sierra Controlled Release Agriform 18-8-13 appliedpreplant at 200 pounds nitrogen/acre.

** CR 18-8-13 + 15-15-15 = Scotts Sierra Controlled Release Agriform 18-8-13applied preplant at 100 pounds nitrogen/acre + 15-15-15 applied at a rate of100 pounds nitrogen/acre.

Varied a Des, Fotos, Comision Californiana

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