*The Genetic Diversity of Strawberry Species, the Underutilized Gene Pool and the Need… DOI: http://dx.doi.org/10.5772/intechopen.102962*

hexaploid species, [11, 108, 117, 120] as can be seen in the summary of **Table 3**. This desirable quality could acquire more relevance as more strawberry is grown in the tropics, as macro trends in crop expansion suggest for the near future. The opposite character, which is resistant to high temperatures during summer, could be important in certain latitudes, although except for Darrow [11], there was only recently interest in this stress as a cause of inhibition of flowering in short-day and day-neutral cultivars, when daytime temperatures are around 26°C [4].

Adaptation to deficits and excesses of moisture is documented for some strawberry species [6, 11, 108, 117, 121] (**Table 3**), and considering the current and future growing environments, both characteristics can be valuable, particularly a gradient related to the efficient use of water, or in other words, cultivars that require the fewer amount of water per kg of fruit produced, since most of the strawberries are grown under irrigation, and this is an input whose availability for agricultural use is less and less.

Other qualities that are found in wild species and are of great economic and environmental importance are those related to resistance to alkaline pH, salinity, and efficient use of iron in those soils [6, 11, 117]. In many of the countries where strawberries are grown, there are problems of iron deficiencies (**Figure 4**), induced by the alkaline pH of the soils, a problem that is partially solved with the application of iron in different forms. It has been observed that there is genetic variation for the efficient use of iron by certain cultivars and octoploid species of strawberry [122, 123], but unfortunately, on many occasions, there are no genotypes available that have this quality and are also adapted and productive to cultivation environments, where these nutritional deficiencies are manifested [122] (**Figure 5**).

**Figure 5.** *Clones with genes of Fragaria chiloensis resistant to iron deficiencies planted in an alkaline pH soil of Irapuato, Gto., Mexico.*

On the other hand, non-renewable inputs such as the use of synthetic fertilizers, could be better used by incorporating in modern cultivars the genes that confer a more efficient use of them, qualities present in certain wild species [73, 124, 125] and that until now have not been used (**Table 3**).

## **3.4 Characters associated with sensory and nutraceutical quality**

Strawberry has a long history of genetic improvement for traits associated with the sensory quality of the fruit. Certainly, since ancient times, the aborigines of the new world [12, 120, 125, 126], practiced selection for some organoleptic characteristics such as fruit weight, color, firmness and flavor, outstanding attributes that have been reported in the landrace's varieties of Chile [124–127]. These qualities, which are under genetic control, have been incorporated into commercial cultivars of

*The Genetic Diversity of Strawberry Species, the Underutilized Gene Pool and the Need… DOI: http://dx.doi.org/10.5772/intechopen.102962*


#### **Table 4.**

*Characteristics of sensory and nutraceutical qualities of strawberry in F. x ananassa, and other wild species of strawberry.*

*F. xananassa*. The large fruit size and firmness undoubtedly came from *F. chiloensis* ssp. *chiloensis* f. *chiloensis* [11]. Clones with large fruit have been identified in other species such as *F. daltoniana* and *F. nilgerrensis* [11, 117]. The firmness of fruit, which is a highly appreciated quality in strawberries, derived from *F. chiloensis* [125, 126] has also been found in certain diploid species [107, 117] (**Table 4**).

Color, flavor and aroma are attributes of the fruit that influence consumer acceptance [128]. The genetic diversity for these traits is partially documented. For example, for color it is possible to find a range of tones from albino to red in some species [11, 129, 130], the same happens with the flavor where outstands certain octoploids and diploids, while aroma *F. moschata* is recognized as a species that is above all [117] (**Table 4**).

Nutritional qualities of strawberries were documented since the previous century for the high content of vitamin C, as much or more than some citrus fruits, and Hansen and Waldo demonstrated in 1944 its genetic control in commercial strawberry cultivars [75]. Evaluations of California's cultivars showed a range of 50 to 100 mg of vitamin C per 100 g fresh weight, with 'Tufts' standing out [131] (**Table 4**).

With the medical recognition of the benefits for human health of certain bioactive compounds such as flavonoids and polyphenols [132], in addition to the already known properties of vitamins and minerals, and with the confirmation that the strawberry belongs to the group of fruits with high content of these substances, its consumption increased and there was an interest in increasing the nutraceutical properties of strawberries, through genetic improvement [3].

Research groups of some prestigious institutions have identified some important compounds, their presence in cultivars [133], and certain cases, which are the strawberry species whose contents are higher and can be the appropriate genetic source for these traits to be transferred to new cultivars. For example, wild plants with a high content of cyanidin, a type of anthocyanin, that helps to reduce risks of type 2 diabetes, certain types of cancer and heart problems, were identified in *F. chiloensis* [134] (**Table 4**).

Diamanti et al. [3], identified certain wild clones of *F. virginiana* ssp. *glauca* with high antioxidant content, and through interspecific hybridization, followed by three cycles of backcrosses, managed to recombine strawberry genotypes with high potential yield and with a higher content of anthocyanins, polyphenols and greater antioxidant capacity, than the cultivar 'Romina'. This is a cutting-edge genetic improvement approach, since the results suggest that it is possible to reconcile in this particular case, a high biomass yield with a higher content of bioactive compounds.
