Alternative fruit fly control for market access and to enhance IPM in eggplant

Eggplant was identified as another fruit fly host commodity where recent changes to interstate market access requirements are causing problems for industry. The proposed research aims to develop a systems approach to meet interstate market access requirements.

Fate of potassium fertilisers applied to clay soils under rainfed grain cropping in south-east Queensland, Australia

Negative potassium (K) balances in all broadacre grain cropping systems in northern Australia are resulting in a decline in the plant-available reserves of K and necessitating a closer examination of strategies to detect and respond to developing K deficiency in clay soils. Grain growers on the Red Ferrosol soils have increasingly encountered K deficiency over the last 10 years due to lower available K reserves in these soils in their native condition. However, the problem is now increasingly evident on the medium-heavy clay soils (Black and Grey Vertosols) and is made more complicated by the widespread adoption of direct drill cropping systems and the resulting strong strati. cation of available K reserves in the top 0.05-0.1 m of the soil pro. le. This paper reports glasshouse studies examining the fate of applied K fertiliser in key cropping soils of the inland Burnett region of south-east Queensland, and uses the resultant understanding of K dynamics to interpret results of field trials assessing the effectiveness of K application strategies in terms of K availability to crop plants. At similar concentrations of exchangeable K (K-exch), soil solution K concentrations and activity of K in the soil solution (AR(K)) varied by 6-7-fold between soil types. When K-exch arising from different rates of fertiliser application was expressed as a percentage of the effective cation exchange capacity (i.e. K saturation), there was evidence of greater selective adsorption of K on the exchange complex of Red Ferrosols than Black and Grey Vertosols or Brown Dermosols. Both soil solution K and AR(K) were much less responsive to increasing K-exch in the Black Vertosols; this is indicative of these soils having a high K buffer capacity (KBC). These contrasting properties have implications for the rate of diffusive supply of K to plant roots and the likely impact of K application strategies (banding v. broadcast and incorporation) on plant K uptake. Field studies investigating K application strategies (banding v. broadcasting) and the interaction with the degree of soil disturbance/mixing of different soil types are discussed in relation to K dynamics derived from glasshouse studies. Greater propensity to accumulate luxury K in crop biomass was observed in a Brown Ferrosol with a KBC lower than that of a Black Vertosol, consistent with more efficient diffusive supply to plant roots in the Ferrosol. This luxury K uptake, when combined with crops exhibiting low proportional removal of K in the harvested product (i.e. low K harvest index coarse grains and winter cereals) and residue retention, can lead to rapid re-development of stratified K profiles. There was clear evidence that some incorporation of K fertiliser into soil was required to facilitate root access and crop uptake, although there was no evidence of a need to incorporate K fertiliser any deeper than achieved by conventional disc tillage (i.e. 0.1-0.15 m). Recovery of fertiliser K applied in deep (0.25-0.3 m) bands in combination with N and P to facilitate root proliferation was quite poor in Red Ferrosols and Grey or Black Vertosols with moderate effective cation exchange capacity (ECEC, 25-35 cmol(+)/kg), was reasonable but not enough to overcome K deficiency in a Brown Dermosol (ECEC 11 cmol(+)/kg), but was quite good on a Black Vertosol (ECEC 50-60 cmol(+)/kg). Collectively, results suggest that frequent small applications of K fertiliser, preferably with some soil mixing, is an effective fertiliser application strategy on lighter clay soils with low KBC and an effective diffusive supply mechanism. Alternately, concentrated K bands and enhanced root proliferation around them may be a more effective strategy in Vertosol soils with high KBC and limited diffusive supply. Further studies to assess this hypothesis are needed.

Epitypification and phylogeny of Colletotrichum acutatum J.H. Simmonds

Simmonds introduced Colletotrichum acutatum in 1965, validated in 1968, with a broad concept, as demonstrated by the selection of several type specimens from a range of hosts. This has created some confusion in the species concept and identification of C. acutatum. There are no viable ex-type cultures of C. acutatum and furthermore there are no existing cultures of C. acutatum on Carica papaya from the type locality in south-east Queensland. The application of molecular phylogenetic studies to isolates of C. acutatum is only meaningful if the taxonomy is stable and species are properly named. In order to clarify the species concept of C. acutatum, an isolate of Colletotrichum acutatum from Carica papaya from Yandina in Southeast Queensland (Australia) is designated as an epitype. A detailed morphological description is provided. Phylogenies based on a combined ITS and beta-tubulin gene analysis indicate that C. acutatum bears close phylogenetic affinities to C. gloeosporioides and C. capsici. Results also indicate that C. acutatum is monophyletic and there is a close relationship between the epitype and other Australian C. acutatum isolates from Carica papaya. Molecular data, however did not provide further evidence to properly elucidate the taxonomie affinities of C. acutatum especially the holotype and epitype. Our studies indicate that given the complexity of the genus Colletotrichum, there is a need to check previously described type specimens and redesign neotypes where necessary in order to clarify taxonomie uncertainties.

Application of phytotoxicity data to a new Australian soil quality guideline framework for biosolids

To protect terrestrial ecosystems and humans from contaminants many countries and jurisdictions have developed soil quality guidelines (SQGs). This study proposes a new framework to derive SQGs and guidelines for amended soils and uses a case study based on phytotoxicity data of copper (Cu) and zinc (Zn) from field studies to illustrate how the framework could be applied. The proposed framework uses normalisation relationships to account for the effects of soil properties on toxicity data followed by a species sensitivity distribution (SSD) method to calculate a soil added contaminant limit (soil ACL) for a standard soil. The normalisation equations are then used to calculate soil ACLs for other soils. A soil amendment availability factor (SAAF) is then calculated as the toxicity and bioavailability of pure contaminants and contaminants in amendments can be different. The SAAF is used to modify soil ACLs to ACLs for amended soils. The framework was then used to calculate soil ACLs for copper (Cu) and zinc (Zn). For soils with pH of 4-8 and OC content of 1-6%, the ACLs range from 8 mg/kg to 970 mg/kg added Cu. The SAAF for Cu was pH dependant and varied from 1.44 at pH 4 to 2.15 at pH 8. For soils with pH of 4-8 and OC content of 1-6%, the ACLs for amended soils range from 11 mg/kg to 2080 mg/kg added Cu. For soils with pH of 4-8 and a CEC from 5-60, the ACLs for Zn ranged from 21 to 1470 mg/kg added Zn. A SAAF of one was used for Zn as it concentrations in plant tissue and soil to water partitioning showed no difference between biosolids and soluble Zn salt treatments, indicating that Zn from biosolids and Zn salts are equally bioavailable to plants.

Resistance to root-lesion Nematodes for development of molecular markers

This is a sub-project of the Australian Wheat and Barley Molecular Marker Program funded by GRDC and led by Drs Diane Mather and Ken Chalmers of University of Adelaide. In this sub-project we will supply phenotypic data on resistance to two species of root-lesion nematodes (Pratylenchus thornei and P. neglectus) on several populations of wheat doubled haploids. We will also supply existing genotypic data on one doubled haploid population. We will also test one population of doubled haploids (CPI133872/Janz) a second time for resistance to P. thornei and P. neglectus and supply this information to University of Adelaide for the development of molecular markers for use by wheat breeders in selecting for resistance to root-lesion nematodes.