Organogenesis during plant regeneration in cotyledon culture of Trifolium michelianum Savi

Shoots of <em>Trifolium michelianum</em> Savi. could be induced directly from the cotyledonary petiole or through petiole-derived callus on EC6 medium (Mahewswaran and Williams 1984) supplemented with BAP at 4.4, 8.8 and 22.2 µM. The mode of caulogenesis highly depended on cytokinin concentration in the medium. Most of the shoots regenerated into mature plants when transplanted to half-strong MS (Murashige and Skoog 1962). The time of caulogenic determination was set for the first day of culture. The induction of determination for caulogenesis was accompanied by the loss of competence toward root formation. SEM studies revealed that caulogenesis was restricted to the distal end of the cotyledonary petioles, very close to but not at the site of excision. The sites of shoot regeneration were limited to abaxial and lateral surfaces of the petioles.

Plant regeneration from immature embryo culture of Trifolium michelianum savi. - histological observations on adventitious shoot induction

Whole plant regeneration via organogenesis in immature embryo culture of <em>Trifolium michelianum</em> Savi. was obtained. The shoots were induced directly from the hypocotyl or indirectly through callus on EC6 medium supplemented with 0.5 and 5 mg/l BAP, respectively. Sporadically the callus formation was preceded by shoot regeneration. Both shoots obtained directly and via callus regenerated into plants when subcultured on half-strength Murashige and Skoog (MS) medium, free of growth regulators. Histological observations revealed that the shoots were induced directly from the ring of meristematic tissue which was formed at the periphery of the hypocotyl or indirectly from the superficial cells of the callus. Irrespective of the mode of regeneration the shoots were of multicellular origin.

Erratum to: The influence of NaCl salinity and hypoxia on aspects of growth in Trifolium species

The effects of salinity and hypoxia on growth, nutritive value, and ion relations were evaluated in 38 species of Trifolium and 3 check legume species (Trifolium fragiferum, Trifolium michelianum, and Medicago sativa) under glasshouse conditions, with the aim of identifying species that may be suitable for saline and/or waterlogged conditions. In the first set of experiments, plants were grown hydroponically at four NaCl concentrations (0, 40, 80, and 160�mm NaCl) and harvested after exposure to these treatments for 4 weeks. NaCl concentrations up to 160�mM reduced dry matter production in most species; however, there were differences in salt tolerance among species, with T. argutum, T. diffusum, T. hybridum, and T. ornithopodioides performing well under the saline conditions (dry matter production was reduced by less than 20%). Concentrations of Na+ and Cl- in the shoots increased with increasing salinity levels, and species again differed in their capacity to limit the uptake of these ions. Dry matter digestibility at 0�mm ranged from 49.8% (T. palaestinum) to 74.0% (T. vesiculosum) and decreased with increasing NaCl concentrations. A second set of experiments evaluated the tolerance of Trifolium species to hypoxic conditions in the glasshouse. Shoot growth, and to a lesser extent root growth, were reduced in all Trifolium species when plants were exposed to stagnant, non-aerated conditions for 28 days, but T. michelianum, T. resupinatum, T. squamosum, T. nigrescens, T. ornithopodioides, T. salmoneum, and T. fragiferum were the least affected species. All species acclimated to the oxygen-depleted conditions by increasing the gas-filled porosity in the roots. This study has provided information that will assist in the identification of forage species for saline and/or waterlogged areas.

Photoperiod affects the flowering time of field-sown balansa clover

Two cultivars of balansa clover (Trifolium michelianum Savi.) were sown on eight occasions from 14 October 2005 to 5 February 2007 in Canterbury, New Zealand, which gave a range of photoperiod at emergence between 8.6 and 15.7 h. The duration from emergence to flowering was related to the length and direction of change in photoperiod at the time of emergence. Thermal time (Tt) from emergence to flowering was constant at ~620 degree-days for ‘Bolta’ and ~365 degree-days for ‘Frontier’ balansa clover plants, provided they emerged into increasing photoperiods. For plants that emerged into decreasing photoperiods, Tt from emergence to flowering decreased from ~1500 to ~630 degree-days for ‘Bolta’ but was constant at ~690 degree-days for ‘Frontier’. Models are presented to predict the Tt requirement from emergence to flowering for ‘Bolta’, ‘Frontier’ and, based on reanalysed data, CPI45856 balansa clovers in relation to daylength at emergence. These results are discussed in relation to farm sowing and management practices.

Vegetative and reproductive development of balansa clover

The rate of emergence, time of the first mainstem leaf appearance, phyllochron and branch initiation and inflorescence development were quantified for balansa clover (Trifolium michelianum).

The influence of NaCl salinity and hypoxia on aspects of growth in Trifolium species

The effects of salinity and hypoxia on growth, nutritive value, and ion relations were evaluated in 38 species of Trifolium and 3 check legume species (Trifolium fragiferum, Trifolium michelianum, and Medicago sativa) under glasshouse conditions, with the aim of identifying species that may be suitable for saline and/or waterlogged conditions. In the first set of experiments, plants were grown hydroponically at four NaCl concentrations (0, 40, 80, and 160 mm NaCl) and harvested after exposure to these treatments for 4 weeks. NaCl concentrations up to 160 mm reduced dry matter production in most species; however, there were differences in salt tolerance among species, with T. argutum, T. diffusum, T. hybridum, and T. ornithopodioides performing well under the saline conditions (dry matter production was reduced by less than 20%). Concentrations of Na+ and Cl− in the shoots increased with increasing salinity levels, and species again differed in their capacity to limit the uptake of these ions. Dry matter digestibility at 0 mm ranged from 49.8% (T. palaestinum) to 74.0% (T. vesiculosum) and decreased with increasing NaCl concentrations. A second set of experiments evaluated the tolerance of Trifolium species to hypoxic conditions in the glasshouse. Shoot growth, and to a lesser extent root growth, were reduced in all Trifolium species when plants were exposed to stagnant, non-aerated conditions for 28 days, but T. michelianum, T. resupinatum, T. squamosum, T. nigrescens, T. ornithopodioides, T. salmoneum, and T. fragiferum were the least affected species. All species acclimated to the oxygen-depleted conditions by increasing the gas-filled porosity in the roots. This study has provided information that will assist in the identification of forage species for saline and/or waterlogged areas.

Grazing management for regeneration of balansa clover in a cocksfoot pasture

'Bolta' and 'Frontier' balansa clover seedlings were counted through two autumns following a large seed set in November 2006, from monocultures sown in a dryland environment in Canterbury. Following rain on 5 January 2007, 65% of 'Bolta' seed and 54% of 'Frontier' seed emerged. 'Bolta' and 'Frontier' balansa clover seedlings were counted through two autumns following a large seed set in November 2006, from monocultures sown in a dryland environment in Canterbury. Following rain on 5 January 2007, 65% of 'Bolta' seed and 54% of 'Frontier' seed emerged. Keywords: annual legumes, balansa clover, Dactylis glomerata, false break, seed bank, spring closing date, Trifolium michelianum, Trifolium subterraneum.

Production and persistence of annual pasture legumes at five saline sites in southern Australia

Herbage production and persistence of 42 annual pasture legumes from 33 species were measured at five sites across southern Australia. Medicago polymorpha L. was highly productive on soils, particularly those not prone to waterlogging, with soil surface (0–10 cm soil depth) salinity [estimated by electrical conductivity (ECe)] levels in summer of up to 36 dS/m, whereas M. truncatula Gaertn. was productive on ECe levels of at least 11 dS/m. Trifolium michelianum Savi and T. resupinatum L. were highly productive on soils subject to waterlogging, but only where 0–10 cm summer ECe levels were less than 8 dS/m. No commercial species were adapted to highly saline (0–10 cm summer ECe levels >8 dS/m), waterlogged sites. However, Melilotus siculus (Turra) Vitman ex B.D. Jacks. has the potential to fulfil this role, provided an appropriate Rhizobium strain can be selected. Mixtures of species and cultivars should be sown to account for high spatial variability for salinity and waterlogging. Traits for annual legume success in saline landscapes include salinity and waterlogging tolerance in germinating seedlings and mature plants, early flowering, hardseededness and delayed softening of hard seeds. Establishment of regenerating seedlings is associated with the timing of hardseed softening in relation to rainfall events capable of leaching topsoil salts. It is proposed that salinity measurements to determine annual legume suitability for winter-dominant rainfall areas are made in summer or early autumn, when at their highest levels. Transects along salinity and waterlogging gradients are suggested as an alternative method to traditional plots for genotype evaluation.

Sub clover, cocksfoot and lucerne combine to improve dryland stock production

The temporal (seasonal) pattern of dryland pasture and stock production from four cocksfoot based pastures (mixed with balansa, Caucasian, subterranean or white clover), a ryegrass/white clover pasture and a pure lucerne crop were compared over 2 years (2004/05 and 2005/ 06). Subterranean clover with cocksfoot provided high legume content pasture giving higher stock production than other pasture mixtures from August to October. This complemented the high yields and stock production provided by lucerne from mid September to January in 2004/05. However, a dry winter followed by spring snow resulted in lucerne production similar to other pastures in 2005/06. Cocksfoot based pastures provided more maintenance feed than perennial ryegrass during a dry summer (2005/06) but ryegrass/white clover provided higher stock production in wet summer conditions (2004/ 05). These results suggest a range of pasture species are necessary to cope with the seasonal climate variability typically experienced in dryland farm systems. Keywords: balansa clover, Caucasian clover, Dactylis glomerata, Lolium perenne, Medicago sativa, pasture growth rates, ryegrass, sheep production, Trifolium ambiguum, Trifolium michelianum, Trifolium repens, Trifolium subterraneum, white clover