To establish the identity of Fusarium species associated with head blight (FHB) and crown rot (CR) of wheat, samples were collected from wheat paddocks with different cropping history in southern Queensland and northern New South Wales during 2001. CR was more widespread but FHB was only evident in northern NSW and often occurred with CR in the same paddock. Twenty different Fusarium spp. were identified from monoconidial isolates originating from different plant parts by using morphology and species-specific PCR assays. Fusarium pseudograminearum constituted 48% of all isolates and was more frequently obtained from the crown, whereas Fusarium graminearum made up 28% of all isolates and came mostly from the head. All 17 Fusarium species tested caused FHB and all 10 tested caused CR in plant infection assays, with significant ( P < 0.001) difference in aggressiveness among species and among isolates within species for both diseases. Overall, isolates from stubble and crown were more aggressive for CR, whereas isolates from the flag leaf node were more aggressive for FHB. Isolates that were highly aggressive in causing CR were those originating from paddocks with wheat following wheat, whereas those from fields with wheat following maize or sorghum were highly aggressive for FHB. Although 20% of isolates caused severe to highly severe FHB and CR, there was no significant ( P < 0.32) correlation between aggressiveness for FHB and CR. Given the ability of F. graminearum to colonise crowns in the field and to cause severe CR in bioassays, it is unclear why this pathogen is not more widely distributed in Australia.

This paper summarises the key findings from recent research on the population genetics and epidemiology of Fusariumpathogens causing head blight and crown rot of wheat in Australia and how this...

Fusarium species associated with crown rot were isolated and identified from 409 wheat, barley or durum wheat crops from the eastern Australian grain belt between 1996 and 1999. Fusarium...

Fusariumhead blight (FHB) of wheat, caused mainly by a few members of theFusarium graminearumspecies complex (FGSC), is a major threat to agricultural grain production, food safety, and animal health. The severity of disease epidemics and accumulation of associated trichothecene mycotoxins in wheat kernels is strongly driven by meteorological factors. The potential impacts of change in climate are reviewed from the perspective of the FGSC life cycle and host resistance mechanisms influenced by abiotic pressures at the ecological, physiological and molecular level. Alterations in climate patterns and cropping systems may affect the distribution, composition and load of FGSC inoculum, but quantitative information is lacking regarding the differential responses among FGSC members. In general, the coincidence of wet and warm environment during flowering enhances the risk of FHB epidemics, but the magnitude and direction of the change in FHB and mycotoxin risk will be a consequence of a multitude of effects on key processes affecting inoculum dynamics and host susceptibility. Rates of residue decomposition, inoculum production and dispersal may be significantly altered by changes in crop rotations, atmospheric carbon dioxide concentration ([CO₂]), temperature and precipitation patterns, but the impact may be much greater for regions where inoculum is more limited, such as temperate climates. In regions of non-limiting inoculum, climate change effects will likely be greater on the pathogenic rather than on the saprophytic phase. Although the mechanisms by which abiotic stress influences wheat defences againstFusariumspecies are unknown, available data would suggest that wheat may be more susceptible toFusariuminfection under future climate conditions. Additional research in this area should be a priority so that breeding efforts and climate resilient management strategies can be developed.

Graft incompatibility in solanaceous plants was investigated using representative cultivars of tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), and pepper (Capsicum annuum L.). Evaluations of the extent of graft (in)compatibility were made by examining survival percentages, fruit yields, and fruit quality in grafted plants. Tomato/pepper (scion/rootstock) and pepper/tomato grafts were considered severely incompatible, and the tomato/eggplant and eggplant/tomato grafts were considered moderately incompatible, when compared with the compatible homo-specific graft combinations of tomato/tomato, eggplant/eggplant, and pepper/pepper.Three, or 3 and 6 weeks after grafting, the dry weights of scions and rootstocks, carbohydrate concentrations in stems above and below the graft unions, scion mineral nutrient concentrations, water potentials of scions, and xylem hydraulic conductivities were measured in the grafted plants. The anatomy of the graft unions was also observed. Growth inhibition and high mortality in tomato/pepper and pepper/tomato grafts (i.e., severe graft incompatibility) was due to discontinuities in the vascular bundles at the graft union, which prevented the translocation of assimilates, mineral nutrients, and water between scions and rootstocks. Reductions in fruit yield and/or fruit quality of tomato/eggplant and eggplant/tomato grafts (i.e., moderate graft incompatibility) may have been due to differences in the requirements for assimilates and mineral nutrients between tomato and eggplant. Plant responses to graft incompatibility varied in solanaceous plants depending on the scion and rootstock combination.