Abstract
To expand the gene pool and introduce new traits to the tetraploid cultivars of Vaccinium corymbosum from wild diploid species V. myrtillus, it is necessary to double the chromosome number in diploid species in order to overcome a post zygotic crossing barrier and a strong triploid block, existing within the genus Vaccinium. Five genetically diverse bilberry genotypes were selected from 21 accessions taken from the breeding collection of the National Institute of Horticultural Research (Skierniewice, Poland) for this study. The bilberry genotypes were derived from the Polish locations of Bolimów Landscape Park, Budy Grabskie and forest complex Zwierzyniec (Łódź Province), and habitats in Norway. The selection of genotypes was made based on the analysis of amplified fragment length polymorphism (AFLP-PCR). Analysis of the Jaccard similarity indexes and the UPGMA method revealed that the examined accessions formed two main groups on the dendrogram. The first group consisted of accessions from Norway, while the second group agglomerated Polish accessions. A further two classes were distinguished in the Polish group: the first included accessions from Budy Grabskie and the second from Zwierzyniec, located ca. 9 km from Budy Grabskie. In order to obtain plant material for in vitro polyploidisation, in vitro shoot cultures of the selected accessions were initiated and multiplied. Both antimitotics used, colchicine and APM, induced tetraploids for all of the accessions. The obtained tetraploids were multiplied, rooted ex vitro and grown in a greenhouse and then in a field. The first flowering was observed in 1.5-year-old plants, either diploid or tetraploid. Diploids bloomed slightly earlier and more profusely than tetraploid plants. Compared to diploids, autotetraploids had significantly larger flowers by ca. 64% and larger pollen tetrads by ca. 35%. The germination capacity of pollen tetrads was high in tetraploids (87.8%), although slightly lower than in diploids (94.3%). After pollinating the flowers of three highbush blueberry cultivars with pollen from the bilberry tetraploid accession, J-4-4x, the plants formed fruits, some of which contained properly formed seeds. The effectiveness of interspecific crossing between V. corymbosum and tetraploid V. myrtillus, defined as the percentage of obtained seedlings in relation to the number of pollinated flowers, was highest (53.3%) in the blueberry ‘Liberty’, and lower in ‘Bluecrop’ and ‘Northland’, 14.8% and 10.0%, respectively. Before using the seedlings for further breeding, their hybridity will be confirmed by molecular markers and the phenotype will be evaluated.
Highlights
The fruits of bilberry (Vaccinium myrtillus L.) are one of the richest sources of biologically active compounds, mainly phenolics, including anthocyanins
The selection of genotypes for polyploidisation was made based on the analysis of genetic differences between bilberry accessions using amplified fragment length polymorphism (AFLP) markers
In vitro cultures and polyploidisation were performed for all five genotypes according to the same procedures described below
Summary
The fruits of bilberry (Vaccinium myrtillus L.) are one of the richest sources of biologically active compounds, mainly phenolics, including anthocyanins. Their total content ranges from 300 to 1200 mg/100 g of F.W., which is much higher than in other Vaccinium species [1,2,3]. The fruits of highbush blueberry cultivars commonly grown commercially in Poland and throughout the world contain, on average, about 200 mg/100 g. Shows the fastest growing trend in fruit production in Poland [4]. Rapid changes in agricultural technology and growing interest in the consumption of blueberry fruits due to their prohealth benefits have directed breeders’
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