Meristem culture and subsequent micropropagation of Chilean strawberry (Fragaria chiloensis (L) Duch. )

BACKGROUND: Vegetative propagation of Fragaria sp. is traditionally carried out using stolons. This system of propagation, in addition to being slow, can spread plant diseases, particularly serious being viral. In vitro culture of meristems and the establishment of micropropagation protocols are important tools for solving these problems. In recent years, considerable effort has been made to develop in vitro propagation of the commercial strawberry in order to produce virus-free plants of high quality. These previous results can serve as the basis for developing in vitro-based propagation technologies in the less studied species Fragaria chiloensis. RESULTS: In this context, we studied the cultivation of meristems and establishment of a micropropagation protocol for F. chiloensis. The addition of polyvinylpyrrolidone (PVP) improved the meristem regeneration efficiency of F. chiloensis accessions. Similarly, the use of 6-benzylaminopurine (BAP) in the culture media increased the average rate of multiplication to 3-6 shoots per plant. In addition, the use of 6-benzylaminopurine (BAP), had low levels (near zero) of explant losses due to oxidation. However, plant height as well as number of leaves and roots were higher in media without growth regulators, with average values of 0.5 cm, 9 leaves and 4 roots per plant. CONCLUSIONS: For the first time in Chilean strawberry, meristem culture demonstrated to be an efficient tool for eliminating virus from infected plants, giving the possibility to produce disease free propagation material. Also, the addition of PVP into the basal MS medium improved the efficiency of plant recovery from isolated meristems. Farmers can now access to high quality plant material produced by biotech tools which will improve their technological practices.

Biosynthesis of flavonoids in achenes of Fragaria chiloensis ssp. chiloensis / Biosintesis de flavonoides en aquenios de Fragaria chiloensis ssp. chiloensis

Fragaria chiloensis ssp. chiloensis has two native botanical forms. Fruits from both botanical forms, Fragaria chiloensis ssp. chiloensis f. chiloensis (native white strawberry) and f. patagonica (native red strawberry), were collected from Bio-Bio Region, and a comparative study in the biosynthesis and pigment accumulation was performed from achens. The fruit was classified in four different developmental and ripening stages in order to establish the differences in the transcriptional profile of structural genes and the chemical compounds. A differential expression of those genes involved in the biosynthesis (phenylpropanoid and flavonoids) of anthocianins was found. The differential expression of genes was concomitant with the increase in the level of cyanidin 3-glucoside (C3G) along the fruit development for both botanical forms. On the contrary, undetectable level of cyanidin 3-glucoside (P3G) was observed in the f. chiloensis. Albeit, P3G increase rapidly from the development stage 2, reaching the maximum value at stage 4 in Fragaria chiloensis ssp. chiloensis f. patagonica.

Fragaria chiloensis ssp. chiloensis presenta dos formas botánicas nativas. Los frutos de ambas formas botánicas, Fragaria chiloensis ssp. chiloensis f. chiloensis (frutilla nativa blanca) y f. patagonica (frutilla nativa roja), fueron colectadas en la región del Bio-Bio, realizándose un estudio comparativo en la biosíntesis y acumulación de la pigmentación en aquenios. Para ello, el fruto fue clasificado en cuatro distintos estadios de desarrollo y maduración a fin de establecer las diferencias en los perfiles transcripcionales de genes estructurales y de compuestos químicos. Se determinó una expresión diferencial de los genes responsables de la formación de antocianinas, concomitante con un incremento en los niveles de cianidina 3-glucósido (C3G) en tanto avanza el desarrollo del fruto en ambas formas botánicas. Por el contrario, se observó niveles indetectables de pelargonidina 3-glucósido (P3G) en f. chiloensis, lo cual contrasta con lo observado en f. patagonica, donde P3G se incrementa rápidamente a partir del estadio 2, alcanzando un máximo valor en estadio 4.