ISHS Acta Horticulturae 403: International Symposium on Cultivar Improvement of Horticultural Crops. Part 2: Fruit Crops
THE CULTURE REGIME SUITABLE FOR THE RESCUE OF HYBRID EMBRYOS IN ACTINIDIA |
| Authors: | M. Shihkin, A. Hexiang, C. Darong, Lena G. Fraser, C. F. Harvey |
| Abstract:
Interspecific hybridisation in Actinidia is restricted by endosperm abortion and abnormal differentiation and development of early embryos. Among three of 11 cross-combinations A. chinensis var. chinensis. X A. melanandra var. melanandra X A. melanandra X A. chinensis and A. arguta X A. chinesis. the abortion of 90% of hybrid seed is presumably due to early embryo lethality as endosperm is normal in development while embryos are dead. Most of the seeds derived from other combinations contain endosperm and embryos at all developmental stages, The proportion of various stages of embryos is different for different combinations. The embryos could be categorised into two types: one which can be rescued in vitro despite their size and development stage, and another which never responded to in vitro rescue under our conditions. For the rescue of older embryos, the best media are MS (or LS) + 1 ppm of Zeatin (or 2ip) + 0.5 ppm IAA + 0.5 ppm GA3, MS(or LS) + 0.5 ppm IAA, and MS (orLS) + 0.5 ppm of GA3. Almost 90–95% of these embryos geminate and grow to normal seedlings. For the rescue of early heart stage embryos, the presence in the cultures of part or all of the endosperm as nurse tissue is beneficial, A successful first culture medium for immature embryos was MS (or LS) + 0.01 – 0.05 ppm GA3 + 8% mannitol, A similar high osmotic potential medium with 0.5 ppm GA3 and 1 ppm Zeatin was also essential for late heart-shaped embryos Approximately 20% of the rescued embryos from the cross A. chinensis var. chinensis X A. melanandra var. melanandra, 16% from A. melanandra X A. chinensis, 20% from A, arguta X A. deliciosa and 30% from A. arguta X A. chinensis germinate and develop to normal seedlings. Chromosome counts have confirmed the expected chromosome number of hybrids between A. deliciosa No. 26 X A. arguta, A. deliciosa cv. Hayward X A. eriantha and A. chinensis var. chinensis X A. melanandra var. melanadra. In addition, the isoperoxidase banding patterns have been determined for the hybrid A deliciosa No. 26 X A. arguta. Female seedlings from some combinations are now at fruiting stage. In conclusion the technique and media used here have been successfully rescuing the embryos of many interspecific crosses in Actinidia and enabled hybrid plants to be reared. | |
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