The effect of foliar sprays of the synthetic auxin 3-5-6 TPA, on fruit drop, fruit size and seed development in three lychee (Litchi chinensis) cultivars: Tai So, Fay Zee Sui and Kwai Mai Pink.

Fruit drop in lychee can cause major yield losses in Australia, the severity varying with cultivar and season. Research in China, South Africa and Israel has demonstrated the potential for synthetic auxins used as foliar sprays to reduce fruit drop in lychee. Trials were initiated in Australia to test the efficacy of the synthetic auxin, 3-5-6 Trichloro-2-phridyl-oxyacetic acid (3-5-6 TPA) at 50 ppm on the cultivars Tai So, Fay Zee Sui and Kwai Mai Pink. Results indicate that in most cases the TPA reduced natural fruit drop however the size of the fruit at the time of application affects the response and the ideal application time varies with cultivar; approximately 13 mm fruit length in 'Kwai Mai Pink', 20 mm in 'Fay Zee Sui' and 27 mm in 'Tai So'. If applied too early in 'Tai So', it caused an increase in fruit drop. The TPA was most effective when natural fruit drop was high, reducing fruit drop from 74.7 to 34.9% in 'Kwai Mai Pink' and least effective when natural fruit drop was low. An increase in the percentage of fruit with poorly developed (chicken tongue) seed and slightly larger fruit size was also observed in treated trees.

Seed production of Stylosanthes guyanensis. 3. Effects of pre-harvest desiccation.

Strips within commercial crops of Stylosanthes guyanensis in the Mareeba district of north Queensland were sprayed with diquat 4, 6 and 10 days before harvest and compared with unsprayed strips. Pre-harvest desiccation made combine harvesting easier, but did not increase harvest yield. Where seed formation and maturation was still possible, desiccation prevented this without substantially increasing the loss of seed to the ground; increased harvest efficiency was thus offset by a diminished quantity of standing seed. However, where there was little or no further potential for seed development, diquat had virtually no effect on the quantity of standing seed or harvest efficiency. It was concluded that the results warranted neither recommendation nor further evaluation of preharvest desiccation of S. guyanensis seed crops.

The effect of different levels of inbreeding on self-incompatibility and inbreeding depression in pineapple

A high level of heterozygosity in domesticated pineapple is one of the main obstacles hindering the efficient development of new varieties. Selfing has been proposed as a strategy to minimise this heterozygosity through the development of parentals with a greater level of homozygosity. Selfing and a range of lesser levels of inbreeding were evaluated for their effects on seed production and inbreeding depression in the early growth of seedlings. Selfing produced few seeds, and very few viable seedlings. The paternal backcross and several half-sib combinations exhibited minimal effects on seed development or early growth and in some cases were similar to the outcross. Sibcrosses were generally unsuccessful. The highest inbreeding coefficient that was not associated with severe inbreeding depression was approximately 0.25. The effect of inbreeding depression and the level of homozygosity on several quantitative traits including those related to fruit quality within the inbred populations, is now being assessed.

Effect of foliar herbicides on the germination and viability of Siam weed (Chromolaena odorata) seeds located on plants at the time of application.

This paper reports a field study undertaken to determine if the foliar application of herbicides fluroxypyr (150 mL 100 L-1 a.i.) and metsulfuron-methyl (12 g 100 L-1 a.i.) were capable of reducing the germination and viability of Chromolaena odorata (L.) R.M.King & H.Rob. (Siam weed) seeds at three different stages of maturity. After foliar application of fluroxypyr germination of mature seeds was reduced by 88% and intermediate and immature seeds were reduced by 100%, compared to the control. Fluroxypyr also reduced the viability of mature, intermediate and immature seeds by 79, 89 and 67% respectively, compared to the control. Metsulfuron-methyl reduced germination of intermediate and immature seeds by 53 and 99% respectively compared to the control. Viability was also reduced by 74 and 96% respectively, compared to the control. Mature seeds were not affected by metsulfuron-methyl as germination and viability increased by 2% and 1% respectively, as compared to the control. These results show that these herbicides are capable of reducing the amount of viable seed entering the seed bank. However depending on the treatment and stage of seed development a percentage of seeds on the plants will remain viable and contribute to the seed bank. This information is of value to Siam weed eradication teams as plants are most easily located and subsequently treated at the time of flowering. Knowledge of the impact of control methods on seeds at various stages of development will help determine the most suitable chemical control option for a given situation.

Reciprocal and advanced generation hybrids between Corymbia citriodora and C-torelliana: forestry breeding and the risk of gene flow

Corymbia F1 hybrids have high potential for plantation forestry; however, little is known of their reproductive biology and potential for genetic pollution of native Corymbia populations. This study aims to quantify the influence of reproductive isolating barriers on the success of novel reciprocal and advanced generation Corymbia hybrids. Two maternal taxa, Corymbia citriodora subsp. citriodora and Corymbia torelliana, were pollinated using five paternal taxa, C. citriodora subsp. citriodora, C. torelliana, one C. torelliana x C. citriodora subsp. citriodora hybrid and two C. torelliana x C. citriodora subsp. variegata hybrids. Pollen tube, embryo and seed development were assessed. Reciprocal hybridisation between C. citriodora subsp. citriodora and C. torelliana was successful. Advanced generation hybrids were also created when C. citriodora subsp. citriodora or C. torelliana females were backcrossed with F1 hybrid taxa. Prezygotic reproductive isolation was identified via reduced pollen tube numbers in the style and reduced numbers of ovules penetrated by pollen tubes. Reproductive isolation was weakest within the C. citriodora subsp. citriodora maternal taxon, with two hybrid backcrosses producing equivalent capsule and seed yields to the intraspecific cross. High hybridising potential was identified between all Corymbia species and F1 taxa studied. This provides opportunities for advanced generation hybrid breeding, allowing desirable traits to be amplified. It also indicates risks of gene flow between plantation and native Corymbia populations.

Seed production of Stylosanthes guyanensis. 1. Growth and development.

The pattern of growth and development of seed crops of stylo (Stylosanthes guyanensis) was derived from measurements made on experimental and commercial crops in north Queensland. The three cultivars Cook, Endeavour, and Schofield differed appreciably only in the timetable of their development. Each had distinct successive phases of vegetative and reproductive development culminating in total annual seed production of 700-800 kg ha-1 from a healthy closed canopy, the main recorded cause of reduced production being the disease Botrytis sp. In a healthy crop of Cook, the peak quantity of standing seed represented almost 90 per cent of the total accountable seed, and the rise to and decline from this peak proceeded at rates of the order of 3-4 per cent per day. It is deduced that, although there appears to be little potential for either increase in overall production or improvement in synchronization or retention characteristics beyond that currently attained by a closed canopy of healthy plants, there is scope for an increase in the efficiency of recovery of standing seed. Maximum recovery will be achieved through attention to choice of time of harvest, presentation of a minimum amount of extraneous vegetation to the harvester, and improvement in harvester separation.

Modeling chickpea growth and development: Nitrogen accumulation and use

Quantitative information regarding nitrogen (N) accumulation and its distribution to leaves, stems and grains under varying environmental and growth conditions are limited for chickpea (Cicer arietinum L.). The information is required for the development of crop growth models and also for assessment of the contribution of chickpea to N balances in cropping systems. Accordingly, these processes were quantified in chickpea under different environmental and growth conditions (still without water or N deficit) using four field experiments and 1325 N measurements. N concentration ([N]) in green leaves was 50 mg g-1 up to beginning of seed growth, and then it declined linearly to 30 mg g-1 at the end of seed growth phase. [N] in senesced leaves was 12 mg g-1. Stem [N] decreased from 30 mg g-1 early in the season to 8 mg g-1 in senesced stems at maturity. Pod [N] was constant (35 mg g-1), but grain [N] decreased from 60 mg g-1 early in seed growth to 43 mg g-1 at maturity. Total N accumulation ranged between 9 and 30 g m-2. N accumulation was closely linked to biomass accumulation until maturity. N accumulation efficiency (N accumulation relative to biomass accumulation) was 0.033 g g-1 where total biomass was -2 and during early growth period, but it decreased to 0.0176 g g-1 during the later growth period when total biomass was >218 g m-2. During vegetative growth (up to first-pod), 58% of N was partitioned to leaves and 42% to stems. Depending on growth conditions, 37-72% of leaf N and 12-56% of stem N was remobilized to the grains. The parameter estimates and functions obtained in this study can be used in chickpea simulation models to simulate N accumulation and distribution.

NIR model development and robustness in prediction of melon fruit total soluble solids

Near infrared spectroscopy (NIRS) can be used for the on-line, non-invasive assessment of fruit for eating quality attributes such as total soluble solids (TSS). The robustness of multivariate calibration models, based on NIRS in a partial transmittance optical geometry, for the assessment of TSS of intact rockmelons (Cucumis melo) was assessed. The mesocarp TSS was highest around the fruit equator and increased towards the seed cavity. Inner mesocarp TSS levels decreased towards both the proximal and distal ends of the fruit, but more so towards the proximal end. The equatorial region of the fruit was chosen as representative of the fruit for near infrared assessment of TSS. The spectral window for model development was optimised at 695-1045 nm, and the data pre-treatment procedure was optimised to second-derivative absorbance without scatter correction. The 'global' modified partial least squares (MPLS) regression modelling procedure of WINISI (ver. 1.04) was found to be superior with respect to root mean squared error of prediction (RMSEP) and bias for model predictions of TSS across seasons, compared with the 'local' MPLS regression procedure. Updating of the model with samples selected randomly from the independent validation population demonstrated improvement in both RMSEP and bias with addition of approximately 15 samples.

Achievements in forest tree genetic improvement in Australia and New Zealand 2: Development of Corymbia species and hybrids for plantations in eastern Australia

This paper describes the establishment of provenance seedling seed orchards of three spotted gums and cadaga (all species of Corymbia ex Eucalyptus). It also discusses the limitations of growing the spotted gums as pure species including: lack of mass flowering, susceptibility to a fungal shoot blight and low amenability to vegetative propagation. These limitations, together with observation of putative natural hybrids of the spotted gums with cadaga, and the early promise of manipulated hybrids, led to an intensive breeding and testing program. Many hybrid families have significant advantages in growth and tolerance to disease, insects and frost, and can be vegetatively propagated. They also exhibit broad environmental plasticity, allowing the best varieties to be planted across a wider range of sites than the spotted gums, resulting in more land being suitable for plantation development.

Seed production of Stylosanthes guyanensis. 2. The consequences of defoliation.

The consequences of defoliation on seed production of stylo (Stylosanthes guyanensis) were examined in field experiments at Walkamin in north Queensland. The practical aim of defoliation is to present a level uncompacted crop canopy to the harvester without a reduction in the quantity of seed carried at harvest ripeness. It was concluded that the latest date at which defoliation is reasonably certain to achieve its objectives is about four weeks before first flower initiation. In north Queensland, this means late February for cvv. Cook and Endeavour and early April for cv. Schofield. The results suggest that development of the population of individual shoots must be synchronized to produce the highest peaks of standing seed; that this is best achieved by ensuring that a closed crop canopy with a ceiling shoot population exists at the time of first flower initiation; and that poorly synchronized shoot development is a consequence of defoliating too late and a cause of reduced seed production.

Wastewater remediation options for prawn farms - Aquaculture Industry Development Initiative 2002-04.

There are many potential bioremediation approaches that may be suitable for prawn farms in Queensland. Although most share generally accepted bioremediation principles, advocacy for different methods tends to vary widely. This diversity of approach is particularly driven by the availability and knowledge of functional species at different localities around the world. In Australia, little is known about the abilities of many native species in this regard, and translocation and biosecurity issues prevent the use of exotic species that have shown potential in other countries. Species selected must be tolerant of eutrophic conditions and ecological shifts, because prawn pond nutrient levels and pathways can vary with different assemblages of autotrophic and heterotrophic organisms. Generally, they would be included in a constructed ecosystem because of their functional contributions to nutrient cycling and uptake, and to create nutrient sinks in forms of harvestable biomass. Wide salinity, temperature and water quality tolerances are also valuable attributes for selected species due to the sometimes-pronounced effects of environmental extremes, and to provide over-wintering options and adequate safety margins in avoiding mass mortalities. To practically achieve these bioremediation polycultures on a large scale, and in concert with the operations of a prawn farm, methods involving seed production, stock management, and a range of other farm engineering and product handling systems need to be reliably achievable and economically viable. Research funding provided by the Queensland Government through the Aquaculture Industry Development Initiative (AIDI) 2002-04 has enabled a number of technical studies into biological systems to treat prawn farm effluent for recirculation and improved environmental sustainability. AIDI bioremediation research in southern Queensland was based at the Bribie Island Aquaculture Research Centre (BIARC), and was conducted in conjunction with AIDI genetics and selection research, and a Natural Heritage Trust (NHT) funded program (Coast and Clean Seas Project No.717757). This report compilation provides a summary of some of the work conducted within these programs.

Lobster aquaculture development in Indonesia, Vietnam and Australia

This project will support the sustainable development of lobster farming in Indonesia to meet global demand for tropical lobsters at high prices (>$US60 /kg). It will also address sustainability issues for the lobster farming industry in Vietnam and provide verification of lobster growout at commercial scale in Australia. The project will adapt technologies developed in Vietnam and apply them in Indonesia to establish a village-based industry for impoverished coastal communities. The Australian component will assess land-based growout systems to prepare for the likely availability of hatchery-reared lobster seed. Hatchery technology is currently being commercialised in Queensland through a partnership between DEEDI and Lobster Harvest Pty Ltd.

Spiny lobster aquaculture development in eastern Indonesia, Vietnam and Australia

The project was successful across all objectives, making demonstrable progress in support of establishing tropical lobster farming in Indonesia. The industry remains most active in Lombok where lobster seed resources are most abundant, and impact has been greatest there. Nevertheless, project activities have established activity and interest in lobster farming in other provinces and particularly Aceh and, South and Southeast Sulawesi. The project met all of its 23 milestones with the exception of publishing a production manual, which has been held over until 2017. For several milestone activities, further research will be required to build on the outcomes generated and reach practical commercial outputs. The research was instigated to address the opportunity to establish a significant small-holder based industry in Indonesia that could alleviate poverty in coastal communities. The premise was that such an industry – lobster farming, had been established in Vietnam, with ACIAR involvement, and it could be replicated in Indonesia where the availability of necessary basic requirements had been confirmed through a previous ACIAR project focussed in Vietnam (FIS/2001/058). The broad aim was to assess, develop and expand the resources of naturally settling lobster seed (puerulus), and develop grow out of those seed to meet export market demand. This was to be achieved by adapting and transferring to Indonesia technology from Vietnam, where lobster farming had become a successful industry producing 1,500 tonnes of export quality lobsters valued at $A100 million.

Innovative management of herbicide resistant weeds - seed banks and soil biology

The project will evaluate seed bank depletion of key northern herbicide resistant weeds under different environments, cropping systems, crop agronomies and non-chemical control tactics. The project will also evaluate soil biology and seed bank relationships to explain differences in seed bank persistence.

Rapid microsatellite marker development for African mahogany ( Khaya senegalensis, Meliaceae) using next-generation sequencing and assessment of its intra-specific genetic diversity.

Khaya senegalensis (African mahogany or dry-zone mahogany) is a high-value hardwood timber species with great potential for forest plantations in northern Australia. The species is distributed across the sub-Saharan belt from Senegal to Sudan and Uganda. Because of heavy exploitation and constraints on natural regeneration and sustainable planting, it is now classified as a vulnerable species. Here, we describe the development of microsatellite markers for K. senegalensis using next-generation sequencing to assess its intra-specific diversity across its natural range, which is a key for successful breeding programs and effective conservation management of the species. Next-generation sequencing yielded 93943 sequences with an average read length of 234bp. The assembled sequences contained 1030 simple sequence repeats, with primers designed for 522 microsatellite loci. Twenty-one microsatellite loci were tested with 11 showing reliable amplification and polymorphism in K. senegalensis. The 11 novel microsatellites, together with one previously published, were used to assess 73 accessions belonging to the Australian K. senegalensis domestication program, sampled from across the natural range of the species. STRUCTURE analysis shows two major clusters, one comprising mainly accessions from west Africa (Senegal to Benin) and the second based in the far eastern limits of the range in Sudan and Uganda. Higher levels of genetic diversity were found in material from western Africa. This suggests that new seed collections from this region may yield more diverse genotypes than those originating from Sudan and Uganda in eastern Africa.