Identification and chromosome doubling of Fragaria mandshurica and F. nilgerrensis

Abstract

Genetic factors that control various excellent agronomic traits are present in wild strawberries; however, barriers such as ploidy differences and interspecific incompatibility prevent the transmission of these genetic factors to cultivated strawberries. Using the colchicine method to induce doubling, the autotetraploids of Fragaria mandshurica and F. nilgerrensis were obtained, and the biological characteristics of the autotetraploids and the compatibility status distribution in different cross-pollination combinations relating to the two species were further examined. The autotetraploids showed thicker and stronger morphological characteristics than those of their corresponding diploids, especially the F. mandshurica species. The change in ploidy can cause the appearance of new excellent agronomic traits: the autotetraploid of F. nilgerrensis is more resistant to anthracnose disease, caused by Colletotrichum gloeosporioides, than the diploid, and the flowering period is significantly longer, with an increase in flower quantity. There is unilateral incompatibility between the two self-compatible species. The autotetraploids are similar to the corresponding diploid in pollination compatibility; however, due to the decline in pollen viability, the related hybridisation combinations show slightly lower compatibility. The closer the ploidy is, the easier it is to obtain hybrid offspring; the tetraploids of both species crossed with cultivated strawberries, showing possible increases in compatibility after chromosome doubling.