Modelling Leaf Production and Crop Development in Maize (Zea mays L.) After Tassel Initiation Under Diverse Conditions of Temperature and Photoperiod

Prediction of the initiation, appearance and emergence of leaves is critically important to the success of simulation models of crop canopy development and some aspects of crop ontogeny. Data on leaf number and crop ontogeny were collected on five cultivars of maize differing widely in maturity and genetic background grown under natural and extended photoperiods, and planted on seven sowing dates from October 1993 to March 1994 at Gatton, South-east Queensland. The same temperature coefficients were established for crop ontogeny before silking, and the rates of leaf initiation, leaf tip appearance and full leaf expansion, the base, optimum and maximum temperatures for each being 8, 34 and 40 degrees C. After silking, the base temperature for ontogeny was 0 degrees C, but the optimum and maximum temperatures remained unchanged. The rates of leaf initiation, appearance of leaf tips and full leaf expansion varied in a relatively narrow range across sowing times and photoperiod treatments, with average values of 0.040 leaves (degrees Cd)-1, 0.021 leaves (degrees Cd)-1, and 0.019 leaves (degrees Cd)-1, respectively. The relationships developed in this study provided satisfactory predictions of leaf number and crop ontogeny (tassel initiation to silking, emergence to silking and silking to physiological maturity) when assessed using independent data from Gatton (South eastern Queensland), Katherine and Douglas Daly (Northern Territory), Walkamin (North Queensland) and Kununurra (Western Australia).

Effects of rootstock and nitrogen fertiliser on postharvest anthracnose development in Hass avocado

These rootstock and nitrogen fertiliser studies confirmed that rootstock race can significantly affect the development of postharvest disease and mineral nutrient accumulation in Hass avocado fruit. When Hass (Guatemalan race) was grafted to seedling Velvick (West Indian race) rootstock, the severity and incidence of anthracnose in fruit were significantly reduced by up to 64 and 37%, respectively, compared with seedling Duke 6 (Mexican race) rootstock. Stem-end rot was also influenced by rootstock in some seasons, and significant reductions (up to 87%) in the severity and incidence of stem-end rot were recorded in Hass fruit from Velvick compared with Duke 6 rootstock trees. These improvements in postharvest diseases were associated with significantly lower concentrations of nitrogen and potassium, higher concentrations of calcium and magnesium, lower ratios of nitrogen:calcium and higher ratios of calcium + magnesium:potassium in Hass leaves and fruit from Velvick compared with Duke 6 rootstock trees. Altering the rate of nitrogen fertiliser had minimal impact on postharvest disease development. However, in one season, reducing the rate of nitrogen fertiliser to nil significantly reduced the concentration of nitrogen in the fruit skin, decreased the nitrogen:calcium ratio and significantly reduced the severity and incidence of anthracnose in Hass fruit from both Velvick and Duke 6 rootstock trees. The form of nitrogen fertiliser (ammonium compared with nitrate) applied to the trees did not significantly affect the postharvest disease susceptibility of Hass avocado fruit on either Velvick or Duke 6 rootstock. The Guatemalan race rootstocks, Anderson 8 and Anderson 10, were also found to be superior to the Mexican race rootstock, Parida 1, for reducing anthracnose severity. This again, was associated with a better balance of mineral nutrients (significantly lower nitrogen:calcium and higher calcium + magnesium:potassium ratios) in the fruit. This rootstock effect, however, was only observed in the first season of a 3-year experiment, possibly because of a better balance between vegetative growth and fruit production in Parida 1 in the latter two seasons. Significant positive correlations between anthracnose severity and fruit skin nitrogen:calcium ratios were evident across all experiments.

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.

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.

ACIAR Improving soil health in support of sustainable development in the Pacific

The proposed project focuses on developing research-based indicators that growers and extensionists can use to assess soil health status (including key chemical, physical and biological variables), as well as extension approaches to communicate soil health.