Characteristics of promising strawberry varieties and elite forms by chemical composition and genes of the aromatic complex of fruits

The results of the analysis of promising strawberry genotypes by the chemical composition and genes, involved in the determination of fruit aroma, are presented. By the complex of chemical traits, the strawberry varieties and elite forms of breeding of the I.V. Michurin Federal Scientific Center are highlighted: Flora (sugars – 9.2%, ascorbic acid – 65.0 mg/100 g, anthocyanins – 74.2 mg/100 g), elite seedling 56-5 (Gigantella Maxim × Privlekatelnaya) (sugars – 8.1%, ascorbic acid – 83.5 mg/100 g, anthocyanins – 64.3 mg/100 g). These strawberry forms are also characterized by a homozygous state of the functional allele of the FaOMT gene of the aromatic complex of fruits, which indicates high mesifurane content in fruits. The research results can be used in further work on the creation of strawberry varieties with a high level of taste and aromatic qualities, and also the antioxidant value of the fruits.


Introduction
Strawberry (Fragaria × ananassa Duch.) is one of the most popular and widely cultivated berry crops in the world. Modern strawberry breeding programs are focused on the creation of new varieties with increased resistance to pests and diseases, and high nutritional and taste-aromatic qualities of fruits [1].
Many Russian and foreign researchers [2][3][4][5] note a high antioxidant potential and therapeutic and prophylactic properties of strawberry fruits, associated with the accumulation of sugars, dietary fiber, minerals and vitamins (ascorbic acid, folic acid and polyphenols).

Materials and methods
The studies were carried out in 2015-2020. Biological material was represented by promising foreign strawberry varieties and strawberry varieties and elite forms, created in "I.V. Michurin Federal Scientific Center".
The content of the components of the chemical composition of fruits was determined by standard methods: the soluble solids content was determined by refractometric, the sugars content -by Bertrand method, the organic acids content -by titration with 0.1 N NaOH in terms of citric acid, the ascorbic acid content -by iodometric method, the anthocyanins content -by pH differential spectrophotometry [8,9]. Statistical analysis of the obtained results was carried out using the package of mathematical statistics Microsoft Excel 2016.
The genes of the aromatic complex of fruits were identified using diagnostic DNA markers. Extraction of total strawberry DNA was carried out according to the DArT protocol with additions [10]. The FaFAD1 gene controlled the γ-decalactone content in fruits was identified with the dominant marker FaFAD1 [7]. The allelic state of the FaOMT gene controlled the mesifurane content in fruits was identified with the codominant marker FaOMT-SI/NO [6]. The polymerase chain reaction was carried out in a T100 thermal cycler (Bio-Rad) in the modes described earlier [11]. Amplification products were separated by electrophoretic method in agarose gel.

Results and discussion
According to the obtained data (Table 1), the strawberry varieties Lastochka and Flora (breeding of "I.V. Michurin Federal Scientific Center") are characterized by high level of the chemical composition of fruits, exceeding the control (variety Elianny) in terms of the content of soluble solids and sugars. The high content of soluble solids and sugars was also characteristic of the strawberry elite seedlings 35-5 (922-67 × Maryshka) and 56-51 (Gigantella Maxim × Privlekatelnaya). All analyzed strawberry varieties and elite forms have moderate acidity of fruits, corresponding to the values recommended for strawberry (no more than 1.5%). Strawberry fruits are of particular value as a source of ascorbic acid (vitamin C). The highest ascorbic acid content (80.0 mg/100 g or more) was characteristic of the strawberry elite seedlings 56-5 and 56-51 (Gigantella Maxim × Privlekatelnaya) (Figure 1). Anthocyanins are the most important polyphenolic compounds of strawberry fruits, determining not only the attractive color of the fruit, but also their antioxidant properties, and their suitability for fruit processing. The smallest anthocyanins content was characteristic of the strawberry variety Arosa (24.2 mg/100 g). The highest anthocyanins content was characteristic of the strawberry variety Flora (74.2 mg/100 g) (Figure 2). https://doi.org/10.1051/bioconf/20213601012 FSRAABA 2021 The FaFAD1 gene among the studied strawberry genotypes was identified only in the variety Arosa. Strawberry varieties Lastochka, Flora, Asia, Clery, Selva and Elianny, and elite forms 56-5 and 56-51 are characterized by the absence of the FaFAD1 gene. It should be noted that the strawberry elite forms 56-5 and 56-51 were identified in the crossing combination Gigantella Maxim × Privlekatelnaya, in which, according to previous studies [11], the variety Gigantella Maxim is characterized by the presence of the FaFAD1 gene. Therefore, the probability of obtaining strawberry genotypes with the FaFAD1 gene in this combination is 50%.

Conclusion
Thus, the results of the studies show, that varieties and promising elite seedlings of strawberry, created in the "I.V. Michurin Federal Scientific Center" are characterized by high levels of chemical composition, not inferior (and in some cases superior) to modern foreign strawberry varieties. According to the complex of chemical traits of fruits, strawberry variety Flora (sugars -9.2%, ascorbic acid -65.0 mg/100 g, anthocyanins -74.2 mg/100 g) and strawberry elite form 56-5 (Gigantella Maxim × Privlekatelnaya) (sugars -8.1%, ascorbic acid -83.5 mg/100 g, anthocyanins -64.3 mg/100 g) were identified. These genotypes are also characterized by the homozygous state of the functional allele of the FaOMT gene of the aromatic complex of fruits. The obtained results can be used in breeding to create strawberry varieties with more attractive fruits in terms of sensory perception of taste, aroma and antioxidant value.