S19 - Session O2 - Assessment of the phenotype and ability to cross of bilberry autotetraploids (Vaccinium myrtillus L.) with highbush blueberry (V. corymbosum L.)

Authors: Malgorzata Podwyszynska *, Katarzyna Mynett, Monika Markiewicz, Stanis322aw Pluta, Agnieszka Marasek-Cio322akowska

The aim of our research was to obtain autotetraploids of bilberry ( V. myrtillus ) capable of crossing with cultivated species of highbush blueberry ( V. corymbosum) . Rapid changes in horticultural technology and growing interest in the consumption of blueberry fruits due to their pro-health benefits have directed breeders' attention to develop improved cultivars. However, highbush blueberry cultivars with purple fruit flesh, containing high anthocyanin content, are not available yet. The fruit flesh of cultivated Vaccinium species is translucent (colourless) as it does not contain anthocyanins. In contrast, the bilberry is characterised by purple fruit flesh. To introduce new traits, e.g. anthocyanin containing flesh to the tetraploid cultivars of V. 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, a strong triploid block, existing within the genus Vaccinium . In previous studies, several autotetraploids were induced in vitro for five genetically diverse bilberry accessions. The obtained tetraploids were multiplied in vitro, rooted ex vitro, 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 leaves, flowers and pollen tetrads. The germination capacity of pollen tetrads was high in tetraploids (ca. 90%) and comparable to diploids. After pollinating the flowers of three highbush blueberry cultivars ('Liberty', 'Bluecrop' and 'Northland') with pollen from the bilberry tetraploid accessions, the plants formed fruits and some of them contained properly formed seeds. The effectiveness of interspecific crossing between V. corymbosum and tetraploid V. myrtillus , a few seedlings were obtain for each of the crosses with these blueberry cultivars. The hybridity of the seedlings was confirmed by molecular markers. Before using the seedlings for further breeding their phenotype will be evaluated.