Swainsona Formosa Research Articles

Welcome to the Peoples of the Mountains and the Sea: Evaluating an Inaugural Indigenous Cultural Festival

Welcome to the Peoples of the Mountains and the Sea: Evaluating an Inaugural Indigenous Cultural Festival

Pollen viability and stigma receptivity in Swainsona formosa (G.Don) J.Thompson (Fabaceae), an ornamental legume native to Australia

Pollen viability and stigma receptivity are prerequisites for successful cross-pollination and seed set in Swainsona formosa. In this study, the pollen viabilities and stigma receptivities was assayed by in vitro pollen germination and simple hand-pollination method on glasshouse-grown plants, respectively. The viability of pollen grains was tested under three different storage conditions: 1) pollen grains were left on the plant in the glasshouse under natural conditions, 2) pollen grains were harvested and kept at a low temperature (4 o C) in total darkness, and 3) pollen grains were kept in a dry freezer (-10 o C) and in total darkness. Meanwhile, stigma receptivity was determined by hand-pollination using fresh pollen grains on flower of glasshouse-grown plants at one day before anther dehiscence up to 8 days after anther dehiscence. The results showed that pollen grains could be stored at 4 o C for up to 28 days without significantly losing their viability. Pollen longevity could be extended beyond two months when stored at -10 o C and under dry conditions. These findings provided a simple and economically sound method for storage of S. formosa pollen. In addition, stigma receptivity was found to be receptive from one day before anther dehiscence and reached its peak within four days after anther dehiscence. These results provide a valuable background to the conventional breeding of this species to create hybrids through cross-pollination

Assessment of pollen viability and germination in Swainsona formosa (G.Don) J.Thompson

The work presented here was aimed at investigating the proper time (after spreading) for viability assessment and the effect of various sucrose concentrations on pollen germination in Swainsona formosa. The rate of pollen tube formation was determined for freshly shed pollen grains of glasshouse-grown plants at 10, 15, 20, 25, 30, 60 and 120-minute intervals after being plated on Brewbaker and Kwack (BK) medium. The results indicated that within 60 minutes pollen germination reached 63.70%, after which remained steady at 120 minutes (63.71%). Under the effect of various concentrations of sucrose, i.e. 0.5, 10, 15, and 20% (w/v), the germination rate of pollen grains was assessed at 60 minutes following germination. The results showed that sucrose concentration of 10 – 15% (w/v) produced better germination rate (64.14%) compare to lower concentrations (19.64 and 43.58% at zero and 5% sucrose, respectively). Sucrose concentration above 15% was also found to inhibit pollen germination (48.92% at sucrose concentration of 20%).

THE DETECTION OF THE TIME OF CONVERSION FROM VEGETATIVE TO REPRODUCTIVE GROWTH IN Swainsona formosa (FABACEAE)

The induction of chromosome doubling using antimitotic chemical will only be effective when the substance is applied at vegetative growth phase, as it works only during mitotic division within cells of actively growing tissues. Therefore, this investigation was carried out to determine the precise conversion time from vegetative into reproductive growth stage, that in turn can be used as a reliable reference for the application of antimitotic chemicals in doubling the chromosome number in Swainsona formosa. The conversion from vegetative to reproductive growth in Swainsona formosa was successfully determined with particular emphasis on the effect of different photoperiods. Although photoperiod affected the time required for first flower initiation, the number of nodes before the plant entering the reproductive stage was not affected by photoperiod and presumed to be set genetically. It was found that under artificial photoperiods of 16, 12 and 8 hours the 12th and 11th nodes were the critical nodes for the main and side stems, respectively. Meanwhile the 10th and 8th nodes were found to be critical for main and side stems of plants grown under natural photoperiods ranging from 12 to 16 hours during their life cycle. Histological examination indicated that when the plants were grown under 12 – 16 hours photoperiods the first floral bud formation was initiated within 56 – 60 days after germination, thus this period was considered as the critical time for the conversion from vegetative to reproductive growth in S. formosa.
 
 Keywords: Sturt’s desert pea, legume, ornamental plant, plant breeding.

The Production of Tetraploid Swainsona formosa by Colchicine Mutagenesis

Swainsona formosa, a legume native to Australia, is a spectacular flowering plant that is used as a hanging basket, container or cut flower plant. Its breeding programme had been emphasized on the production of better flower quality through ploidy modification to produce tetraploid plants. Colchicine, an antimitotic chemical, had been sucessfully used to induce tetraploidyzation in S. formosa. Up to 50% of plants with double chromosome number (2n = 4x = 32) were produced by seedling application of colchicine at 0.01%–0.1%. Concentrations below 0.01% or above 0.1% were found not effective in inducing chromosome doubling. Tetraploid S. formosa were charaterized by larger leaflets, bigger size but lower density of stomata, larger flowers with longer peduncles and larger pollen grains with lower viability. In general, colchicine can be used effectively to induce polyploidyzation in S. formosa and this method should find application in breeding programme.

Papilionoid inflorescences revisited (Leguminosae-Papilionoideae)

The inflorescence structure determines the spatiotemporal arrangement of the flowers during anthesis and is therefore vital for reproductive success. The Leguminosae are among the largest angiosperm plant families and they include some important crop plants. In papilionoid legumes, the raceme is the most common type of inflorescence. However, a range of other inflorescence types have evolved via various developmental processes. A (re-)investigation of inflorescences in Swainsona formosa, Cicer arietinum, Abrus precatorius, Hardenbergia violacea and Kennedia nigricans leads to new insights into reduction mechanisms and to a new hypothesis on the evolution of the papilionoid pseudoraceme. Inflorescence morphology and ontogeny were studied using scanning electron microscopy (SEM). The inflorescence in S. formosa is an umbel with a rare type of pendulum symmetry which may be triggered by the subtending leaf. Inflorescences in C. arietinum are reduced to a single flower. An early formed adaxial bulge is the sterile apex of the inflorescence (i.e. the inflorescence is open and not terminated by a flower). In partial inflorescences of A. precatorius, the axis is reduced and its meristem is relocated towards the main inflorescence. Flower initiation follows a peculiar pendulum pattern. Partial inflorescences in H. violacea and in K. nigricans show reduction tendencies. In both taxa, initiated but early reduced bracteoles are present. Pendulum symmetry in S. formosa is probably associated with distichous phyllotaxis. In C. arietinum, strong reduction tendencies are revealed. Based on studies of A. precatorius, the papilionoid pseudoraceme is reinterpreted as a compound raceme with condensed lateral axes. From an Abrus-like inflorescence, other types can be derived via reduction of flower number and synchronization of flower development. A plea is made for uniform usage of inflorescence terminology.

Role of Proanthocyanidins in Resistance of the LegumeSwainsona formosatoPhytophthora cinnamomi

Reduced flower pigmentation in the legume Swainsona formosa is associated with increased susceptibility to Phytophthora cinnamomi and other soil-borne pathogens. This study aimed to identify the mechanism for these differences in susceptibility. Chemical analyses of stem tissues that had been previously inoculated with P. cinnamomi revealed that neither anthocyanin nor total phenolic content increased with infection. Such results suggested that observed differences in susceptibility, as indicated by flower colour, were related to preformed rather than induced stem chemistry. Acetone extracts from healthy, uninfected stem tissues of a red-flowered line were highly toxic to the fungus, while extracts from a white-flowered line were non-toxic and those from a pink-flowered line were intermediate in toxicity and this was correlated with the total phenolic and proanthocyanidin concentration of the extracts. Precipitation of proanthocyanidins with bovine serum albumen removed the toxicity of the extracts. It was concluded that differences in the proanthocyanidin content of tissues contributed to the differences in disease susceptibility of plants with different flower colours.

Pretreatment Stress Enhances Embryogenic Callus Production in Anther Culture of Sturt's Desert Pea (Swainsona formosa)

The aims of the experiment were to investigate the effect of pretreatment stress on the proliferation of anther-derived embryogenic callus, and its subsequent embryo regeneration in Swainsona formosa. Anthers were pretreated in starvation medium at cold (4 °C) temperature and cultured. Cultures were initially placed in darkness for four weeks, followed by 16-h photoperiod at 25 ± 1 °C. The stress pretreatment was found to enhance embryogenic callus formation on cultured anthers. Further, somatic embryos were successfully regenerated from embryogenic callus upon transferred onto regeneration medium supplemented with 1% sucrose and 4.63 µM kinetin, and later plantlets were obtained. Meanwhile, nonembryogenic callus continued to grow resulting in more callus mass without showing any embryoid initiation.

Flower colour is associated with susceptibility to disease in the legumeSwainsona formosa

The hypothesis that plants of the ornamental Australian native legume Swainsona formosa (Sturt’s desert pea) with reduced flower pigmentation are more susceptible to soilborne diseases was investigated using red, pink and white-flowered lines challenged with Phytophthora cinnamomi. Inoculations of roots, hypocotyls and detached stems showed that the red line was completely resistant, the white line highly susceptible, and the pink line intermediate in reaction. Similar results were obtained for root and detached stem assays using Pythium irregulare and Fusarium solani isolated from diseased white-flowered plants, but all lines were equally susceptible to Botrytis cinerea in detached stem assays. Crosses between the red and white lines showed that white flowers and susceptibility to P. cinnamomi were each determined by recessive alleles at single loci, which segregated together.

Floral ontogeny of Swainsona formosa (Fabaceae: Faboideae: Galegeae)

Swainsona formosa (G.Don) J.Thompson (Sturt’s desert pea) is used in commercial floriculture for cut flowers and ornamental pot plants; however, accurate identification of the growth stages is critically important in making management decisions in floricultural crops. This plant was investigated by stereomicroscopy and scanning electron microscopy (SEM) to identify flowering time and stages of floral development. This is the first work to describe the complete floral ontogeny in a member of tribe Galegeae. Conversion from vegetative to reproductive stages began within 40–46 days after seed germination for axillary branches and within 46–52 days for central stems. Plants required 807.5 days °C growing degree-days for axillary branches and 921.5 days °C for central stems to reach 50% flowering. The central stem grew more nodes (11.1 ± 0.97 nodes) before the initiation of the first flower than did the axillary branches (7.2 ± 0.93 nodes). The order of floral organ initiation within each whorl is unidirectional, except for the petal whorl, which is simultaneous; the flower is organised into five whorls and shows a pentamerous arrangement of sepals and petals, 10 stamens in two whorls and a central carpel.

Embryology of Swainsona formosa (Fabaceae): Anther and Ovule Development

Our study showed that floral morphology and anatomy in Swainsona formosa were typical of leguminous flower. The anthers were found to be tetrasporangiate, with a 3-layered wall below the epidermis. The wall was comprised of a layer of endothecium, middle layer and secretory tapetum. Pollen grains were triporate and shed at a two-cell stage. The ovules were campylotropous with a zigzag micropyle. Multiple embryo sacs were occasionally found but only one mature embryo was formed in the seed. Rubbing the receptive stigma with fingertip enhanced pollination, resulted in 100% pod formation on treated flowers. During fertilization, the pollen tube entered the embryo sac via one of two existing synergids, destroying the synergid in the process. The endosperm was of nuclear type, and only one or two layers of endosperm left as the seed reached its maturity. The seed coat was composed of a single layer of thick-walled palisade cells on the outside followed by a single layer hypodermal sclereids on the inside.

RESEARCH NOTE Floral Bud Length as Morphological Predictor for Microspore Developmental Stage in Sturt’s Desert Pea (Swainsona formosa)

This work was conducted to establish the relationship between microspore developmental stage and length of the floral bud in glasshouse-grown Sturt's desert pea, a native Australian legume. The stages of microspore development were segregated into tetrad, early-uninucleate, mid-uninucleate and late-uninucleate. The results showed that the stage of microspore development was highly dependent on the length of floral bud. The tetrad stage lasted longer than early-, mid- or late-uninucleate stages. The attempted induction of androgenesis in Sturt's desert pea using anthers from floral buds with similar size, as in the present work, was unsuccessful. However, our work showed that the floral bud length can be used as a reliable predictor of microspore developmental stage in Sturt's desert pea. Key words: Sturt's desert pea, Swainsona formosa , androgenesis, legume

Embryology of Swainsona formosa (Fabaceae): Anther and Ovule Development

Our study showed that floral morphology and anatomy in Swainsona formosa were typical of leguminous flower. The anthers were found to be tetrasporangiate, with a 3-layered wall below the epidermis. The wall was comprised of a layer of endothecium, middle layer and secretory tapetum. Pollen grains were triporate and shed at a two-cell stage. The ovules were campylotropous with a zigzag micropyle. Multiple embryo sacs were occasionally found but only one mature embryo was formed in the seed. Rubbing the receptive stigma with fingertip enhanced pollination, resulted in 100% pod formation on treated flowers. During fertilization, the pollen tube entered the embryo sac via one of two existing synergids, destroying the synergid in the process. The endosperm was of nuclear type, and only one or two layers of endosperm left as the seed reached its maturity. The seed coat was composed of a single layer of thick-walled palisade cells on the outside followed by a single layer hypodermal sclereids on the inside.

Root-nodule bacteria from indigenous legumes in the north-west of Western Australia and their interaction with exotic legumes

Bacteria were isolated from root-nodules collected from indigenous legumes at 38 separate locations in the Gascoyne and Pilbara regions of Western Australia. Authentication of cultures resulted in 31 being ascribed status as root-nodule bacteria based upon their nodulation of at least one of eight indigenous legume species. The authenticated isolates originated from eight legume genera from 19 sites. Isolates were characterised on the basis of their growth and physiology; 20 isolates were fast-growing and 11 were slow-growing (visible growth within 3 and 7 d, respectively). Fast-growers were isolated from Acacia, Isotropis, Lotus and Swainsona, whilst slow-growers were from Muelleranthus, Rhynchosia and Tephrosia. Indigofera produced one fast-growing isolate and seven slow-growing isolates. Three indigenous legumes ( Swainsona formosa, Swainsona maccullochiana and Swainsona pterostylis) nodulated with fast-growing isolates and four species ( Acacia saligna, Indigofera brevidens, Kennedia coccinea and Kennedia prorepens) nodulated with both fast- and slow-growing isolates. Swainsona kingii did not form nodules with any isolates. Fast-growing isolates were predominantly acid-sensitive, alkaline- and salt-tolerant. All slow-growing isolates grew well at pH 9.0 whilst more than half grew at pH 5.0, but all were salt-sensitive. All isolates were able to grow at 37 °C. The fast-growing isolates utilised disaccharides, whereas the slow-growing isolates did not. Symbiotic interactions of the isolates were assessed on three annual, one biennial and nine perennial exotic legume species that have agricultural use, or potential use, in southern Australia. Argyrolobium uniflorum, Chamaecytisus proliferus, Macroptilium atropurpureum, Ononis natrix, Phaseolus vulgaris and Sutherlandia microphylla nodulated with one or more of the authenticated isolates. Hedysarum coronarium, Medicago sativa, Ornithopus sativus, Ornithopus compressus, Trifolium burchellianum, Trifolium polymorphum and Trifolium uniflorum did not form nodules. Investigation of the 31 authenticated isolates by polymerase chain reaction with three primers resulted in the RPO1 primer distinguishing 20 separate banding patterns, while ERIC and PucFor primers distinguished 26 separate banding patterns. Sequencing the 16S rRNA gene for four fast- and two slow-growing isolates produced the following phylogenetic associations; WSM1701 and WSM1715 (isolated from Lotus cruentus and S. pterostylis, respectively) displayed 99% homology with Sinorhizobium meliloti, WSM1707 and WSM1721 (isolated from Sinorhizobium leeana and Indigofera sp., respectively) displayed 99% homology with Sinorhizobium terangae, WSM1704 (isolated from Tephrosia gardneri) shared 99% sequence homology with Bradyrhizobium elkanii, and WSM1743 (isolated from Indigofera sp.) displayed 99% homology with Bradyrhizobium japonicum.

Root-nodule bacteria from indigenous legumes in the north-west of Western Australia and their interaction with exotic legumes

Bacteria were isolated from root-nodules collected from indigenous legumes at 38 separate locations in the Gascoyne and Pilbara regions of Western Australia. Authentication of cultures resulted in 31 being ascribed status as root-nodule bacteria based upon their nodulation of at least one of eight indigenous legume species. The authenticated isolates originated from eight legume genera from 19 sites. Isolates were characterised on the basis of their growth and physiology; 20 isolates were fast-growing and 11 were slow-growing (visible growth within 3 and 7 d, respectively). Fast-growers were isolated from Acacia, Isotropis, Lotus and Swainsona, whilst slow-growers were from Muelleranthus, Rhynchosia and Tephrosia. Indigofera produced one fast-growing isolate and seven slow-growing isolates. Three indigenous legumes (Swainsona formosa, Swainsona maccullochiana and Swainsona pterostylis) nodulated with fast-growing isolates and four species (Acacia saligna, Indigofera brevidens, Kennedia coccinea and Kennedia prorepens) nodulated with both fast- and slow-growing isolates. Swainsona kingii did not form nodules with any isolates. Fast-growing isolates were predominantly acid-sensitive, alkaline- and salt-tolerant. All slow-growing isolates grew well at pH 9.0 whilst more than half grew at pH 5.0, but all were salt-sensitive. All isolates were able to grow at 37 °C. The fast-growing isolates utilised disaccharides, whereas the slow-growing isolates did not. Symbiotic interactions of the isolates were assessed on three annual, one biennial and nine perennial exotic legume species that have agricultural use, or potential use, in southern Australia. Argyrolobium uniflorum, Chamaecytisus proliferus, Macroptilium atropurpureum, Ononis natrix, Phaseolus vulgaris and Sutherlandia microphylla nodulated with one or more of the authenticated isolates. Hedysarum coronarium, Medicago sativa, Ornithopus sativus, Ornithopus compressus, Trifolium burchellianum, Trifolium polymorphum and Trifolium uniflorum did not form nodules. Investigation of the 31 authenticated isolates by polymerase chain reaction with three primers resulted in the RPO1 primer distinguishing 20 separate banding patterns, while ERIC and PucFor primers distinguished 26 separate banding patterns. Sequencing the 16S rRNA gene for four fast- and two slow-growing isolates produced the following phylogenetic associations; WSM1701 and WSM1715 (isolated from Lotus cruentus and S. pterostylis, respectively) displayed 99% homology with Sinorhizobium meliloti, WSM1707 and WSM1721 (isolated from Sinorhizobium leeana and Indigofera sp., respectively) displayed 99% homology with Sinorhizobium terangae, WSM1704 (isolated from Tephrosia gardneri) shared 99% sequence homology with Bradyrhizobium elkanii, and WSM1743 (isolated from Indigofera sp.) displayed 99% homology with Bradyrhizobium japonicum.

Water Status and Growth of Callus in Sturt's Desert Pea (Swainsona formosa) as Affected by Media Condition

This work was undertaken to investigate response of callus and the water status of Sturt's desert pea (Swainsona formosa) in vitro under various environmental stress conditions. Water potential of culture media ranged from -0.27MPa to -1.05MPa so that salt and osmotic stress and different concentration of sucrose could be applied to Sturt's desert pea calli grown in the tissue culture media. The percent increase in calli was highest in standard MS medium with 30g L-1 sucrose but was not so when the water potential of medium was adjusted to the same water potential using standard MS plus mannitol. The water potential of callus tissue was almost the same as that of culture media at any range of MS and sucrose concentrations. Turgor of callus tissue did not alter significantly under any stress conditions. It is concluded that the optimum concentration of salt, sucrose and water status of medium could be estimated by this method and that standard MS concentration and its water status are suitable for the formation of Sturt's desert pea calli.

Effect of different types and concentrations of plant growth retardants on Sturt's desert pea ( Swainsona formosa)

Sturt's desert pea ( Swainsona formosa) has potential as a flowering pot plant, if the uneven and excessive vegetative growth can be controlled by the use of growth retardants. Ancymidol, chlormequat, daminozide, flurprimidol and paclobutrazol were applied to Sturt's desert pea (SDP) in glasshouse experiments. Paclobutrazol (PBZ) at 10 mg a.i./plant consistently produced a compact pot plant with more lateral shoots. Flurprimidol at 0.5 and 1 mg a.i./plant reduced main shoot growth but had little effect on lateral shoots. CCC had no significant effect. Ancymidol at 10 or 25 mg a.i./plant and daminozide at 2500 and 5000 mg a.i./plant produced less attractive plants with serious symptoms of toxicity. Suppression of lateral shoot growth required higher concentrations of PBZ and flurprimidol compared to the main shoot.

Micropropagation of adult Swainsona formosa (Leguminosae: Papilionoideae: Galegeae)

Explants of axillary buds excised from mature adult stems of Swainsona formosa (G. Don) J. Thompson (syn. Clianthus formosus) were cultured on Murashige and Skoog medium supplemented with a range of auxins, cytokinins, and sucrose concentrations. Auxins did not increase shoot or bud numbers above controls, and 2,4-dichlorophenoxyacetic acid was the only auxin to significantly increase callus production. Benzyladenine or thidiazuron incorporated into the medium at 0.1 µM stimulated shoot and bud production, and shoot growth occurred following removal of cytokinins from the medium after 4 wk. Shoot number increased linearly with sucrose concentration up to 40 g l−1, but shoot height and the number of cytokinin-induced buds were optimal at sucrose levels of 20–30 g l−1. Roots were initiated in vitro following treatment of cuttings with 0.1% indole-3-butyric acid and 0.1% α-naphthaleneactic acid. Plantlets were successfully established in soil but were plagiotropic and exhibited distichous phyllotaxy.

DISEASE NOTES OR NEW RECORDS: Stem rot of Sturt's desert pea caused by Botrytis cinerea

A stem rot of Sturt’s desert pea was observed in a nursery in New South Wales. Plants were grown under cover and the weather coinciding with the disease outbreak was 2–3 weeks of high humidity. Botrytis cinerea was sporulating profusely on the base of the stem and was isolated from sections of stem tissue. Pathogenicity tests confirmed this fungus as the pathogen.

Translocation of paclobutrazol and gibberellic acid in Sturt's Desert Pea (Swainsona formosa)

The translocation patterns of paclobutrazol and gibberellic acid were studied by applying these plant growth regulators locally to the main or lateral shoots of Sturt's Desert Pea. Paclobutrazol only reduced the growth of shoots to which it was directly applied indicating that it was readily translocated acropetally within a shoot (via xylem) but not basipetally (via phloem), although some phloem translocation has been reported. Gibberellic acid elongated the main shoot and enhanced apical dominance irrespective of the place of application suggesting it is readily translocated both through xylem and phloem. The translocation patterns did not vary between the main or lateral shoots.