Ovule Culture and Embryo Rescue Facilitate Interspecific Hybridisation in Blueberry (Vaccinium Spp.)

Abstract

About 80 blueberry (Vaccinium) accessions represent four species in New Zealand collections. They are highly heterogeneous and constitute a valuable resource as parental material for breeding. However, hybridisation between different species and ploidy levels does not produce viable seed in vivo. To increase the variation available to breeders, and to introgress characters from different species into parental breeding populations, interspecific, interploidy crosses were made. Ovules were cultured aseptically 14, 28 and 35 days after pollination. Embryos were dissected from the enlarged ovules and cultured on regeneration media. From fourteen of these crosses, more than 200 plants regenerated within 6-10 weeks. In ovulo embryo culture was more successful when the maternal parent had a lower ploidy than the male parent. Flow cytometry revealed that 4x × 6x crosses produced pentaploids, while the progeny of 4x × 5x and 5x × 6x crosses had nuclear DNA contents similar to that of the maternal parent. Random Amplified Polymorphic DNA and Simple Sequence Repeat marker analyses are being used to confirm the hybrid nature of these progenies. Hybrid plants are being propagated in vitro, acclimated in the greenhouse and established in field trials. Our study has demonstrated that in vitro ovule culture and embryo rescue can be used to overcome post-zygotic barriers to interspecific hybridisation between Vaccinium species with different ploidy levels.

Parental Bias in Segregation Distortion of RAPD Markers from Solanum Anther-Derived Plants

“…Incidentally this group of 12 distortion-causing markers was found intact in the nine plants (Table 2) having mostly parental traits. Segregation distortion during doubled haploid production is likely to be due to a range of factors including selection during the process of gamete culture and plantlet regeneration [32].Simultaneous presence of group parental markers in anther-derived progeny reported in this study may indicate a linkage with androgenesis in potatoes. Androgenic fitness has an important role in the prevalence of markers with segregation distortion and linkage of such markers to specific genes controlling in vitro androgenesis [ 33].…”

Increased Zygote-Derived Plantlet Formation through In Vitro Rescue of Immature Embryos of Highly Apomictic Opuntia ficus-indica (Cactaceae)

“…Embryo rescue is a biotechnological approach used to overcome some technological difficulties encountered when using traditional plant breeding approaches. Early rescue of hybrid embryos allows the recovery of interspecific and intergeneric hybrids that are impossible to produce in vivo [38,39]. The method is also used to manipulate ploidy in cultivated species [38,40].…”

“…Early rescue of hybrid embryos allows the recovery of interspecific and intergeneric hybrids that are impossible to produce in vivo [38,39]. The method is also used to manipulate ploidy in cultivated species [38,40]. In this study, we explored another possible application of embryo rescue, i.e., to enhance the regeneration of zygotic embryos in O. ficus-indica.…”

Applying Biotechnology in the Propagation and Further Selection of Vaccinium uliginosum × (V. corymbosum × V. angustifolium) Hybrids

“…In vitro technologies made it possible to overcome the negative effect of various factors on seed germination and seedling viability at the initial stages of development, thus allowing the preservation of unique genetic material. Pathirana et al [ 1 ] showed that in vitro cultivation of embryoids allowed postzygotic barriers to be overcome during interspecific hybridization of Vaccinium species with different ploidy levels. In addition, treatment with colchicine allowed viable amphiploids of V. corymbosum × V. ashei hybrids to be obtained in in vitro culture [ 2 ].…”

“…The use of in vitro techniques makes it possible to obtain viable hybrids from seeds that have an underdeveloped embryo and to overcome the negative effect of various factors on seed germination and seedling viability at the initial stages of development. In vitro embryo culture can be used to overcome the barriers of nonbreeding in interspecific hybridization of Vaccinium species with different levels of ploidy [ 1 ]. Furthermore, when treated with colchicine, in vitro culture allows for amphiploid hybrids to be obtained by crossing species of different ploidy, such as V. corymbosum × V. ashei [ 2 ].…”