Effect of cross direction and cultivars on crossability of interspecific hybridization between Vaccinium corymbosum and Vaccinium virgatum

The purpose of this study was to evaluate the effect of cross direction and cultivars on interspecific hybridization between Vaccinium corymbosum (4x) and Vaccinium virgatum (6x). Totally 99 reciprocal interspecific crosses were made by using ten cultivars of V. corymbosum and five cultivars of V. virgatum. Percent fruit set, number of developed seeds per berry, germination rate and number of seedlings per flower were evaluated. The progeny seedlings were obtained from 65% of all cross combinations, and more than 99% of the seedlings were revealed to be pentaploid hybrids by flow cytometric analysis. In the comparison of crossability between interspecific reciprocal crossing, 4x × 6x crosses showed 2.9 times higher rate of mean fruit set (67%) and 3.3 times higher rate of number of seeds per berry (6.2) than the opposite crosses (6x × 4x). However, the average germination rate (38%) of the 6x × 4x crosses was 1.7 times higher than that of 4x × 6x crosses. Consequently, average number of seedlings per flower (0.96) in 4x × 6x was 3.8 times higher than that in the opposite crosses. According to the number of seedlings per flower significant difference in the crossability was found among the cultivars in V. corymbosum in the reciprocal crosses with V. virgatum, whereas no such significant difference was observed in V. virgatum.

► We evaluated the effect of cross direction and cultivars on interspecific hybridization between Vaccinium corymbosum (4x) and Vaccinium virgatum (6x).
► Crossability in 4x × 6x was higher than that in the opposite crosses.
► Significant difference in the crossability was found among the cultivars in only V. corybosum in the reciprocal crosses.