Abstract
This is the first report of molecular markers application for the analysis of endosperm-derived callus and nonaploid kiwifruit (Actinidia chinensis var. deliciosa, formerly: Actinidia deliciosa) plants. As a source of explants, fruits of ‘Hayward’, the most popular cultivar, were used. Additionally, analyses of the nuclear DNA content and sex were conducted on the regenerated plants. Hexaploid seedlings were used as control for the flow cytometric analyses. Most of the plants (about 90%) regenerated via endosperm-derived callus possessed 2C = 9Cx DNA, which confirmed their endosperm origin and nonaploidy. Because Actinidia is a dioecious species, and female plants bearing fruits are desired by breeders, it is crucial to identify the sex of an individual at early stages of development. Analyses were conducted with ex vitro and in vitro samples. Results revealed that specific markers for a Y-chromosome applied at the callus stage allowed us to reliably predict the sex of plants regenerated from it. This is a novel application of sex-linked markers for early selection of female and male callus lines when the sex of the initial explants is still unknown, such as fresh isolated embryos and endosperm. It may have significant importance for breeding kiwifruit programs, which involve tissue culture techniques.
Highlights
Polyploidization, a common phenomenon among plants, plays an important role in the speciation mechanism in a natural environment as well as in breeding programs in agriculture [1,2]
A. chinensis var. deliciosa belongs to the A. chinensis complex, populations of which show different combinations of di, tetra, penta, and hexaploids [8]
Plant regeneration from endosperm was reported for diploid cultivar of A. chinensis [14], for hexaploid kiwifruit A. chinensis var. deliciosa [6,7] ‘Hayward’, only organogenesis and shoot buds formation from endosperm-derived callus were reported [15]
Summary
Polyploidization, a common phenomenon among plants, plays an important role in the speciation mechanism in a natural environment as well as in breeding programs in agriculture [1,2]. One of the techniques used to induce polyploidy is to start with an in vitro culture of endosperm tissue [3,4] This storage tissue has a higher ploidy than the embryo in the majority of Angiosperms. Efforts have been made to obtain kiwifruit plants with different ploidy levels, such as triploids (after pollination with lethally-irradiated pollen [9]) and dodecaploids (during multiplication and unprompted polyploidization [10]). Another method to increase ploidy is the production of interspecific hybrids using crosses between species with different ploidies [11]. Plant regeneration from endosperm was reported for diploid cultivar of A. chinensis [14], for hexaploid kiwifruit A. chinensis var. deliciosa [6,7] ‘Hayward’, only organogenesis and shoot buds formation from endosperm-derived callus were reported [15]
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