A molecular protocol for Early Sex Discrimination (ESD) in Actinidia spp

Dioecism and an extended juvenile phase of 3–7 years in kiwifruit hinder the progress in breeding new cultivars. The identification of fruit-bearing females at an early stage of growth is crucial for breeders. Consequently, molecular markers have become a key tool for identifying female and male plants at an early stage of development. Several efforts were made to identify PCR-based sex linked markers in Actinidia; however, those markers are characterized by a highly polymorphic nature affecting the result of the screening reliability, suggesting the need of more suitable, stable markers, characterized by a consistent transferability among genotypes and species. The main goal of this work was to develop a method for the ultimate discrimination of females from male plants at an early stage of growth using sex-linked markers. We developed an Early Sex Discrimination molecular Test (ESD Test) that allows the discrimination of male and female plants using a simple PCR amplification test. We demonstrate that the test could unequivocally identify the gender of an unknown sample both in the most commercially important species A. chinensis and in further 13 Actinidia species tested with the exception of Actinidia latifolia, where markers fail in gender discrimination. Male genotypes could be easily identified and discarded reducing the cost of a breeding program.