Strawberries. James F Hancock
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chiloensis are either dioecious, gynodioecious or perfect flowered depending on geographical location. North American F. chiloensis are primarily dioecious, with staminate plants being about 10% more common than pistillate (Hancock and Bringhurst, 1979b, 1980). In some cases, apparent males are polygamodioecious and bear a few early fruits. Highly fertile hermaphrodites have been found in California at Año Nuevo and Pigeon Point, Alaska, and in the northern islands off the coast of British Columbia. In Chile, F. chiloensis is largely gynodiecious as all wild plants are either pistillate or hermaphroditic (Lavín, 1997). Plants in Hawaii are all hermaphroditic.
There are four subspecies of F. chiloensis recognized (Staudt, 1989): (i) ssp. lucida (E. Vilmorin ex Gay) Staudt – coast of Pacific Ocean from Queen Charlotte Island to San Luis Obispo, California; (ii) ssp. pacifica Staudt – coast of Pacific Ocean from Aleutian Islands to San Francisco, California; (iii) ssp. sandwicensis (Degener and Degener) – Hawaii; and (iv) ssp. chiloensis (L.) Duch. – beaches and mountains of South America. Two forms of this subspecies are recognized, the cultivated f. chiloensis and the native f. patagonia.
It is believed that the aboriginal people of Chile (Mapuche and Picunche) were the domesticators of F. chloensis ssp. chiloensis f. chiloensis about 1000 years ago and they grew them in small garden plots in coastal areas between latitudes 35°S and 39°S (see Chapter 2, this volume). Consistent with a domestication bottleneck, intersimple sequence repeat (ISSR) genetic diversity in f. chiloensis (Percentage of polymorphic bands (P) = 48%, Nei’s genetic index (h) = 0.12, Shannon’s information index (S) = 0.19) was found to be half of that in f. patagonica (P = 90%, h = 0.25, S = 0.38) (Carrasco et al., 2007).
Recent morphometric and random amplified polymorphic DNA (RAPD) analyses of interspecific variation in F. chiloensis have indicated that ssp. lucida and pacifica might intergrade too much to be considered separate subspecies, but ssp. sandwicensis and chiloensis are distinct (Catling and Porebski, 1998). The major characteristics used to separate the subspecies were hair length, leaflet size, plant colour, petal number and whether the hairs on the leaf stalk were ascending or spreading. Hair orientation was the only reliable way to distinguish ssp. lucida from pacifica.
Several ecotypes of F. chiloensis have been identified in both North and South America. Distinct dune, coastal-strand, headland-scrub and woodland-meadow types are found in California (Table 1.2). They are distinguished primarily by flower number, leaf width, leaf biomass, runner width and resistance to salt and drought stress. The woodland-meadow types may be stabilized hybrid derivatives of F. chiloensis × F. virginiana (Hancock and Bringhurst, 1979b). At least two distinct native races have been described in Chile: a coastal type with dark, more glossy, green leaves, and a higher-elevation form with duller leaves and a blue casting, much like F. virginiana ssp. glauca (Cameron et al., 1993). In a morphometric analysis of Chilean F. chiloensis, del Pozo and Lavin (2005) identified four cluster groups among wild accessions, although they did not specify any climatic or regional patterns to the variability. The most diagnostic characteristics were leaflet size, plant size, weight of fruit and fruit size. Interestingly, white forms of native F. chiloensis were discovered that clustered very closely to the white, much larger-fruited domesticated forms (Fig. 1.6).
Fig. 1.6. Distribution of 61 Chilean accessions of strawberry on the first and second principal components (PC1 and PC2) of a multivariate analysis of morphological traits. Symbols represent accessions of: wild Fragaria chiloensis f. patagonica with red fruit (●); wild F. chiloensis f. patagonica with white fruit (
Native hybridizations between F. vesca and F. chiloensis in coastal California have resulted in persistent 5x, 6x and 9x colonies (Fig. 1.7) (Bringhurst and Senanayake, 1966). These have been named Fragaria × bringhurstii after their discoverer R.S. Bringhurst (Staudt, 1989). Their leaves are intermediate between F. chiloensis and F. vesca with regard to thickness, colour, profile, pubescence and the appearance of the upper leaf surface. They are mostly sterile at 2n = 35, 42 or 63, but small percentages of aneuploid gametes are produced that are interfertile with octoploid material.
Fig. 1.7. The morphological and cytogenetic traits distinguishing F. chiloensis, F. vesca and their pentaploid hybrid at Point Sur, California. (Adapted from Bringhurst and Khan, 1963.)
Fragaria virginiana Duch.
The scarlet or Virginia strawberry is found in meadows throughout central and eastern North America. Plants are slender, tall and profusely runnering (Fig. 1.8). Leaves are coarsely toothed and obovate to oblong. The terminal tooth of the terminal leaflet is usually shorter than the adjacent lateral teeth. The inflorescence is variable, basal to high branching and flowers are small to large (0.6–2.5 cm) and dioecious. The fruit is soft and round, up to 3 cm in diameter (although most fruit is much smaller). It is light red with white flesh, aromatic and has deeply embedded seeds. F. virginiana can be distinguished from F. chiloensis by a number of morphological traits (Table 1.3).
Fig. 1.8. Duchesne’s drawing of Fragaria virginiana. This species is the North American progenitor of the cultivated strawberry, F. × ananassa. (From Darrow, 1966.)
Table 1.3. The characteristics that separate F. chiloensis from F. virginiana. (From Darrow, 1966.)
| Character | F. chiloensis | F. virginiana |
|---|---|---|
| Leaves | Thick, leathery | Thin |
| Deep set stomata | Shallow set stomata | |
| Strongly netted | Not strongly netted | |
| Glossy | Dull | |
| Dark green | Bluish to light green | |
|
Evergreen
|