Breeding biology of two Parakeelya (Australian Calandrinia) species

Wickramasinghe, Priyanka (2011). Breeding biology of two Parakeelya (Australian Calandrinia) species PhD Thesis, School of Agriculture and Food Sciences, The University of Queensland.

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Author Wickramasinghe, Priyanka
Thesis Title Breeding biology of two Parakeelya (Australian Calandrinia) species
Formatted title
Breeding biology of two Parakeelya (Australian Calandrinia) species
School, Centre or Institute School of Agriculture and Food Sciences
Institution The University of Queensland
Publication date 2011-11
Thesis type PhD Thesis
Supervisor Dion K. Harrison
Margaret E. Johnston
Total pages 163
Total colour pages 8
Total black and white pages 155
Language eng
Subjects 07 Agricultural and Veterinary Sciences
Abstract/Summary The ornamental horticulture industry is largely driven by the development and commercialisation of novel plant varieties. Australia has an abundance of native plant species with potential for development as flowering ornamentals, but only a small proportion have actually been cultivated and domesticated. To a large extent, this is due to the effort and cost of domesticating new species, and progress is often impeded by a lack of knowledge of the reproductive and breeding biology. Parakeelya sp. (Mt Clere) and Parakeelya balonensis (Australian Calandrinia; family Montiaceae, formerly in Portulacaceae) are floriferous Australian herbaceous succulents with ornamental potential. To facilitate future breeding and development of a range of new ornamental cultivars from these species, and assess their potential for use in intergeneric breeding with distantly related ornamental Portulaca species (Portulaca grandiflora and Portulaca umbraticola) the objectives of this study were to: (1) understand the cytological and phylogenetic relationships of these four species; (2) characterise their reproductive biology and intergeneric breeding compatibility; (3) establish methods for intergeneric hybridization; and (4) assess their amenably to advanced breeding methods such as somatic polyploidization. Infrageneric and intergeneric phylogenetic relationships of Parakeelya were studied using rDNA ITS sequence data of 37 taxa and chromosome number data of 20 taxa. This is the first comprehensive molecular phylogenetic analysis of Parakeelya, with new rDNA ITS sequence data generated for 13 species and seven accessions, new somatic chromosome counts for 13 species and two accessions, and reconfirmed somatic chromosome counts for three species. There were two infrageneric groups of seven of the eight Parakeelya accessions coincident with somatic chromosomes 2n=18 and 2n=24. The species relationships of Parakeelya schistorhiza (2n=36) could not be clearly clarified using rDNA ITS sequence data and chromosome numbers. All 12 Portulaca accessions studied were monophyletic and clustered mostly according to their morphological taxonomy representing subgenera Portullacella and Portulaca. The nine accessions studied in subgenus Portulaca formed three subclades viz. Oleracea, Pilosa and Umbraticola. Portulaca intraterranea was clustered with Portulaca oleraceae in the subclade Oleracea. The study also found that Portulaca oleracea is genetically diverse with three different ITS sequences. The reproductive biology and breeding compatibility of Parakeelya sp. (Mt Clere), Parakeelya balonensis and two popular garden ornamental Portulaca species (Portulaca grandiflora and Portulaca umbraticola) were studied. This work clearly showed that prefertilization intergeneric breeding incompatibility exists for reciprocal crosses of Portulaca grandiflora  Parakeelya balonensis (2n=18) and Portulaca umbraticola  Parakeelya sp. (Mt Clere) (2n=24). Further, the study found breeding compatibility of intraspecific outcrosses of all four species, partial self-compatibility of Parakeelya sp. (Mt Clere) and Portulaca grandiflora, self-incompatibility of Parakeelya balonensis and Portulaca umbraticola and autogamy of Portulaca grandiflora. To assist future research efforts to overcome these prefertilization breeding barriers using in vitro ovule pollination and embryo rescue, studies were performed to characterize capsule and seed development, and to establish in ovulo embryo culture of intraspecific control crosses and in vitro ovule culture of these four species. The study demonstrated that in ovulo embryo culture is possible for Portulaca umbraticola. Since breeding incompatibility hindered intergeneric hybridization, the efficacy of somatic polyploidization was investigated as a tool to accelerate the domestication of Parakeelya sp. (Mt Clere). For the first time, the study generated fertile colchicine induced tetraploids (2n=48) of Parakeelya sp. (Mt Clere) with novel flower characteristics of ruffled/serrated petal edges and darker red, and wider red and white petal sectors. Stomata density, guard cell length, anther length and flower bud diameter were efficient tools for discerning diploids and tetraploids. However, breeding incompatibility existed between colchicine induced tetraploids and diploids of Parakeelya sp. (Mt Clere), hindering the production of triploid plants. This thesis provides the first reports of the phylogenetic relationships, cytology, reproductive biology, breeding compatibility and polyploidization of Parakeelya sp. (Mt Clere) and Parakeelya balonensis and optimized protocols for future breeding research in these key areas. Hence, it has generated significant and essential new knowledge required for the development of more efficient breeding programmes for the early domestication of Parakeelya sp. (Mt Clere) and Parakeelya balonensis for ornamental horticulture.
Keyword Breeding, Calandrinia, chromosome, hybridization, incompatibility, intergeneric, molecular phylogenetics, Parakeelya, polyploidization, Portulaca.
Additional Notes Colour page numbers: 18, 91, 115, 118, 131, 133, 137, 142. Landscape page numbers: 34, 41, 44, 49, 52, 55, 110, 157, 158, 159, 160, 161, 162, 163.

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Created: Mon, 14 Nov 2011, 22:13:05 EST by Priyanka Wickramasinghe on behalf of Library - Information Access Service