Abstract
‘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.
There is a need in Queensland winter strawberry (Fragaria ×ananassa Duch.) production areas for a highly flavored, early-ripening cultivar to replace or be an alternative to ‘Kabarla’ (Herrington, 1995). ‘Kabarla’ has benefited the Queensland strawberry industry through its high production of fruit early in the season, when market prices are typically high. However the shape of ‘Kabarla’ fruit is often irregular, with a high frequency of small fruit, which limit its marketability when fruit of other cultivars are readily available. ‘Sweet Charlie’ (Chandler et al., 1997) and ‘Earlibrite’ (Chandler et al., 2000a) have been tested in Queensland as early-yielding cultivars, but have not become established because they lack sufficient earliness, resistance to bruising, or uniformity of fruit shape. ‘Strawberry Festival’ (Chandler et al., 2000b) was recently introduced to Queensland and has rapidly become a major early-season cultivar with fruit and plant attributes desirable to growers, although ‘Strawberry Festival’ commences production slightly after ‘Kabarla’. The cultivar ‘Rubygem’ was developed to provide early-season production of high-flavored fruit. ‘Rubygem’ strawberry has produced high early-season (May through August) yields of moderately firm, attractive fruit at the Department of Primary Industries and Fisheries (DPI&F) research stations in Nambour and Cleveland, and in several commercial fields in the Caboolture district in Southeast Queensland. It is recommended for trial in areas with mild winter climates, especially where rainfall is unlikely and a very early, well-flavored berry is required. The name ‘Rubygem’ was chosen after studying a survey presented to consumers because of the consumer appeal of the name, and the flavorful characteristics and color of ‘Rubygem’ fruit.
Origin
‘Rubygem’ originated from a 1998 cross between ‘Earlibrite’ (Chandler et al., 2000a) and ‘Carlsbad’ (Voth et al., 1994). ‘Earlibrite’, a 2000 release from the Florida Agricultural Expt. Sta., was used as a parent because of its high early-season yield potential and its desirable shape and low acidity. ‘Carlsbad’, a 1994 release from the University of California, was used as a parent because of its ability to produce firm, attractive fruit. ‘Rubygem’ was first selected as a desirable genotype based on appearance, flavor, resistance to bruising, and suitable plant characteristics in Queensland during the 1999 season, and was identified as ‘Selection 99-194’ before being released as ‘Rubygem’.
Description
‘Rubygem’ is a short-day cultivar. It has a more compact but upright plant habit than ‘Kabarla’ and is similar to ‘Strawberry Festival’. The leaf color of the upper side is medium green (137B) (Royal Horticultural Society, 1995), with a slightly concave shape in cross-section. Blistering is absent or very weak and glossiness is weak. The terminal leaflet's length-to-width ratio is longer than broad (average, 1.08), with an obtuse shape of the leaf base. Incisions of leaf margins are crenate, and the attitude of hairs on the petiole is strongly outward. Stipule anthocyanin coloration is absent or very weak. The compact plant habit and relatively long and stiff pedicels result in many flowers and fruit that are exposed. This exposure makes the fruit easy to harvest, but also increases its vulnerability to rain damage. ‘Rubygem’ produces fruit that are similar in weight to ‘Strawberry Festival’ (Table 1). Fruit are mostly conical to cordiform, with some short wedge in shape (Fig. 1). However, fruit are not always as regularly shaped as those of ‘Strawberry Festival’. External fruit color is red (44A) and glossy, and the flesh is a medium red (43A) (Royal Horticultural Society, 1995). The calyx is much larger than the fruit diameter, especially on the primary fruit of flushes. Fruit of ‘Rubygem’ are firm yet juicy, and the flavor and overall acceptability of the fruit are as highly regarded as that of ‘Camarosa’ (Table 2).
Cumulative yield, fruit weight, soluble solids, and titratable acidity of ‘Rubygem’ in comparison with selected standard cultivars grown in the field at Cleveland, Queensland, during the 2005 season.
Sensory characteristics of overall, flavor and texture “acceptability,” and juiciness, sweetness, and acidity “just right” of ‘Rubygem’ in comparison with selected standard cultivars in 2005.
Fruit of ‘Rubygem’ strawberry. Grid, 1-cm squares.
Citation: HortScience horts 42, 6; 10.21273/HORTSCI.42.6.1482
Fruit of ‘Rubygem’ strawberry. Grid, 1-cm squares.
Citation: HortScience horts 42, 6; 10.21273/HORTSCI.42.6.1482
Fruit of ‘Rubygem’ strawberry. Grid, 1-cm squares.
Citation: HortScience horts 42, 6; 10.21273/HORTSCI.42.6.1482
Performance
‘Rubygem’ was included in replicated variety trials at Maroochy Research Sta., Nambour, during 2002 through 2005, and Redlands Research Sta., Cleveland, in 2005. Ripe fruit were harvested, graded, counted, and weighed weekly from May through August. Acidity, as percent citric acid equivalents, and soluble solids (ºBrix) were assessed in 2003 and 2005. For postharvest taste panel analysis, ripe fruit were harvested at Redlands Research Sta. 23-25 Aug. 2005 and transported the same day to the sensory evaluation facilities at DPI&F Hamilton, Queensland. Twenty one to 24 untrained panelists were asked to rate a sample of the fruit according to an incomplete block design for “acceptability” of overall, appearance, flavor, and texture; and for firmness, juiciness, sweetness, and acidity in relation to “just right.” Scores were averaged before analysis. Data were analyzed by residual maximum likelihood using GenStat Eighth Edition (Lawes Agricultural Trust, Rothamsted, UK). Cultivars were treated as a fixed effect, and blocks and sessions within blocks were treated as random effects. The significance of cultivars was assessed using the Wald test and, if this test was significant, pairwise comparisons between predicted means were made using Fisher's lsd.
‘Rubygem’ compared favorably with ‘Kabarla’ and ‘Strawberry Festival’ in 2005 at Cleveland (Table 1) and in 2004 at Nambour, where ‘Rubygem’ (173 g/plant) had higher (lsd 0.05, 60 g/plant) early yields to the end of June than ‘Strawberry Festival’ (100 g/plant) and was similar to Kabarla (132 g/plant). ‘Rubygem’ has been shown to have resistance to fusarium wilt (Fusarium oxysporum Schlecht. Ex Fr. f. sp. fragariae, Winks and Williams) at a similar level to ‘Strawberry Festival’ and more resistant than that of ‘Selva’ (Hutton and Gomez, 2006). Although the relative susceptibility to anthracnose fruit rot (Colletotrichum acutatum Simmonds), colletotrichum crown rot (Colletotrichum gloeosporioides Penz.), botrytis fruit rot (Botrytis cinerea Pers. ex Fr.), powdery mildew [Sphaerotheca macularis (Wallr. ex Fr.) Jacz. f. sp. fragariae], or to the two-spotted spider mite (Tetranychus urticae Koch) has not been determined, serious epidemics of these diseases and infestations of this pest have not been observed when appropriate control measures (such as clean planting material, standard fungicide applications, and predatory mite releases) have been used. However, during rain events, fruit of ‘Rubygem’ are more susceptible to cracking (55%) than those of ‘Strawberry Festival’ (30%).
Availability
‘Rubygem’ has been officially registered by DPI&F and Horticulture Australia Limited as ‘DPI Rubygem’. Plants or licenses for ‘Rubygem’ can be accessed through Ekland Marketing Company, P.O. Box 6067, Chico, CA, 95927, and through Garry Fullelove, DPI&F Forestry Science Building, 80 Meiers Road, Indooroopilly, Queensland, 4168 Australia, Garry.Fullelove@dpi.qld.gov.au.
Literature Cited
Chandler, C.K. , Albregts, E.E. , Howard, C.M. & Brecht, J.K. 1997 ‘Sweet Charlie’ strawberry HortScience 32 1132 1133
Chandler, C.K. , Legard, D.E. , Dunigan, D.D. , Crocker, T.E. & Sims, C.A. 2000a ‘Earlibrite’ strawberry HortScience 35 1363 1365
Chandler, C.K. , Legard, D.E. , Dunigan, D.D. , Crocker, T.E. & Sims, C.A. 2000b ‘Strawberry Festival’ strawberry HortScience 35 1366 1367
Herrington, M. 1995 ‘Kabarla’ Plant Varieties J. 8 50 51
Hutton, D. & Gomez, A. 2006 The incidence of fusarium wilt in Queensland cultivars 193 198 Menzel C.M. & Waite G.K. Horticulture Australia projects BS01002, BS04001 and BS05003 Horticulture Australia Ltd Sydney
Royal Horticultural Society 1995 Royal Horticultural Society colour chart Royal Horticultural Society London, UK
Voth, V. , Shaw, D.V. & Bringhurst, R.S. 1994 Strawberry plant called ‘Carlsbad’ United States plant patent no. 8660
