New Zealand Journal of Botany abstract

Graft chimeras and somatic hybrids for new cultivars

G. C. LINDSAY*
M. E. HOPPING

The Horticulture and Food Research Institute of  New Zealand Ltd.
Mt Albert Research Centre
Private Bag 92169,
Auckland, New Zealand

H. BINDING

Botanisches Institut
Christian-Albrechts Universität
D-24098 Kiel, Germany

G. K. BURGE

The New Zealand Institute for Crop and Food  Research Ltd.
Levin Research Centre
Private Bag 4005
Levin, New Zealand
*Present address: Levin Research Centre, Private Bag 4005, Levin, New Zealand.

Abstract  Three techniques were evaluated as methods for plant improvement: protoplast fusion in vitro for somatic hybrids, protoplast co-culture in vitro for chimeras, and graft manipulation in planta for periclinal chimeras. Methods were developed initially for herbaceous, solanaceous species and then evaluated on two species of woody Actinidia.

Protoplasts from tomato (2n = 24) and Bü (a Solanum hybrid obtained by fusing nightshade and dihaploid potato protoplasts, 2n = 96) were fused at laboratories located at Kiel, Germany, and Levin, New Zealand. Identical methods were used at each laboratory, and plants were regenerated from the hybrid callus. At Kiel, only 1.6% of the regenerants were symmetric fusions that contained 120 chromosomes. One chimeric plant remained genomically stable during 3 years of in vitro growth and a further year in the glasshouse. At Levin, 83% of regenerants were asymmetric fusions with additional nightshade or Bü genomes. Some regenerants, however, contained a single nightshade genome. Protoplasts from Actinidia were fused using the methods detailed for the solanaceous plants, but regeneration of plants was not achieved.

Chimeric plants were obtained by co-culturing Bü and tomato plants. At Kiel, 2.1% of the regenerants were chimeric. Co-cultures of protoplasts between Actinidia arguta and A. deliciosa, at Levin, did not produce regenerative callus.

Periclinal chimeras were sought from in planta grafts between tomato and nightshade. Two chimeric shoots were obtained. On the basis of epidermal hair type, pollen compatibility, seed and fruit set, one chimera had the histogenic LI layer of nightshade over LII and LIII histogenic layers of tomato (NTT), and the other had two layers of nightshade over one layer of tomato (NNT). Chimera NTT was more stable than NNT, but both produced axillary shoots with characteristics of the other chimera.

Periclinal chimeras were also sought from graft unions in planta and in vitro between A. arguta and A. deliciosa. From in planta grafts, all adventitious shoots were A. arguta. From in vitro grafts, 75% of the shoots that regenerated were A. deliciosa and none was chimeric.

Each of these techniques has the potential to produce new plants. However, the probability of success was low and therefore a large number of regenerants would be required from which to select the desired plants.

Keywords  Actinidia; chimeras; flow cytometry; isozymes; protoplasts; Solanum hybrid; Lycopersicon

New Zealand Journal of Botany, 1995, Vol. 33: 79-92

0028-825X/95/3301-0079 $2.50/0 (c) The Royal Society of New Zealand 1995

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