New Zealand Journal of Botany abstracts
Diversity of Brassica (Brassicaceae) species
naturalised in Canterbury, New Zealand
P. B. Heenan
R. G. Fitzjohn
M. I. Dawson
Allan Herbarium
Landcare Research
P.O. Box 69
Lincoln, New Zealand
Abstract Field surveys were undertaken of Brassica
naturalised in Canterbury, investigating taxonomic diversity,
morphological variation, distribution, and abundance of naturalised
taxa, crop escapes, and crop–weed hybrids. As a result, six species,
nine varieties, and two natural hybrids were recognised as naturalised
in Canterbury. B. rapa var. oleifera was the most
common taxon, while B. rapa var. chinensis, B. rapa
var. glabra, B. rapa var. rapa, B. napus
var. oleifera, and B. oleracea var. acephala
were less abundant and generally occured in small populations of only a
few individuals in rural areas. Single plants of B. oleracea
var. gongylodes (kohl rabi) and B. napus var. napobrassica
(swede) were collected. An additional species, B. juncea, is
recorded as a new naturalised plant in Canterbury. Most of the Brassica
populations sampled were small, with 64% of the 107 populations
observed comprising fewer than 10 plants.
Flow cytometry profiles were obtained for 168
samples of B. juncea, B. napus, B. oleracea, and B. rapa, and these usually
confirmed morphological identifications to a particular species.
However, there were some identification uncertainties with B. napus, as some plants had a flow
cytometry profile of that species but the morphology of either B. rapa var. oleifera or B. oleracea var. acephala. Tetraploid plants of B. rapa (var. chinensis, var. oleifera, and var. rapa) and B. oleracea var. acephala were recorded. We also
identified two instances of hybridisation. One plant has a flow
cytometry profile and a high percentage of malformed pollen that are
consistent with being the putative interspecific F1 hybrid B. napus × B. rapa. Another population
included plants of the putative intraspecific hybrid B. rapa var. oleifera × B. rapa var. chinensis growing with the two
parental species.
Keywords naturalised plants; crop escapes; Brassica;
B. juncea; B. rapa; B. napus; B. oleracea;
flow cytometry; hybrids; Canterbury flora
B04024; Received 23 June 2004; accepted 19 August 2004; Online
publication date 9 December 2004
New Zealand Journal of Botany, 2004, Vol. 42: 815–832
0028–825X/04/4205–0815 © The Royal Society of New Zealand 2004
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