Selection of new banana varieties for the cool subtropics in Australia

The most destructive disease in the cool subtropics is race 4 Fusarium wilt caused by the root pathogen, Fusarium oxysporum f.sp. cubense (Foc). In many cases whole production areas have or are being destroyed. It was the need to develop Cavendish varieties resistant to Foc that stimulated banana screening and selection programs, as well as non-conventional genetic improvement programs, in Australia, South Africa, Spain and Taiwan. In Brazil, which also has a conventional breeding program, the primary target is to produce a superior AAB dessert banana that is resistant to race 1 Foc. Because of the focus on Foc resistance, selection of varieties better adapted to the subtropics has been a secondary issue. Some unexpected results have come from these selection programs. For instance, Goldfinger (FHIA-01), developed by the Honduran Foundation for Agricultural Research, has been found to be resistant to Foc and Sigatoka (Mycosphaerella fijiensis and M. musicola) but it also shows a remarkable tolerance to the climatic extremes experienced in the cool subtropics. What is even more interesting are indications that the flavour and texture of the fruit develops best in the cool subtropics of New South Wales and Queensland, but not in tropical Queensland. This demonstrates the need to assess genotype x environment interaction for specific traits in different ecological zones within a country. The challenge for the subtropical industries is to develop or select bananas that are better adapted to the climate and pest/disease complexes of that region, but have flavour and characteristics that appeal to consumers. Preferably the fruit should have attributes that are not easily attained in more tropical regions. The introgression of genes may be targeted in some of these programs from cultivars with cold and drought hardiness (ie. Lady Finger (AAB), Mysore (AAB), Ducasse (AAB)). It is also important to study the genetics and heritability of important traits for the subtropics. Results from selection programs in Australia are discussed

Towards the development of a Cavendish banana resistant to race 4 of fusarium wilt: gamma irradiation of micropropagated Dwarf Parfitt (Musa spp., AAA group, Cavendish subgroup)

'Dwarf parfitt', an extra-dwarf Cavendish cultivar with resistance to subtropical race 4 fusarium oxysporum f. sp. cubense 9Foc), was gamma irradiated at a dose of 20 Gy and putative mutants were recovered with improved agronomic characteristics. Further screening of putative mutants for improved yield and fruit size, as well as a degree of resistence to fusarium wilt, led to the selection of a line (DPM25) with improved productivity when grown on soils infested with subtropical race 4 Foc. DPM25 was equal to the industry standard, 'Williams', in every agronomic trait measured and it consistently showed a lower incidence of fusarium wilt. Further improvement of field resistance to race 4 Foc is needed in DPM25 and further cycles of mutation induction and selction is an option discussed

Towards the development of a Cavendish banana resistant to race 4 of fusarium wilt: gamma irradiation of micropropagated Dwarf Parfitt (Musa spp., AAA group, Cavendish subgroup)

'Dwarf parfitt', an extra-dwarf Cavendish cultivar with resistance to subtropical race 4 fusarium oxysporum f. sp. cubense 9Foc), was gamma irradiated at a dose of 20 Gy and putative mutants were recovered with improved agronomic characteristics. Further screening of putative mutants for improved yield and fruit size, as well as a degree of resistence to fusarium wilt, led to the selection of a line (DPM25) with improved productivity when grown on soils infested with subtropical race 4 Foc. DPM25 was equal to the industry standard, 'Williams', in every agronomic trait measured and it consistently showed a lower incidence of fusarium wilt. Further improvement of field resistance to race 4 Foc is needed in DPM25 and further cycles of mutation induction and selction is an option discussed

Metal artifact reduction of CT scans to improve PET/CT

In recent years, different metal artifact reduction methods have been developed for CT. These methods have only recently been introduced for PET/CT even though they could be beneficial for interpretation, segmentation, and quantification of the PET/CT images. In this study, phantom and patient scans were analyzed visually and quantitatively to measure the effect on PET images of iterative metal artifact reduction (iMAR) of CT data. Methods: The phantom consisted of 2 types of hip prostheses in a solution of 18F-FDG and water. 18F-FDG PET/CT scans of 14 patients with metal implants (either dental implants, hip prostheses, shoulder prostheses, or pedicle screws) and 68Ga-labeled prostate-specific membrane antigen (68Ga-PSMA) PET/CT scans of 7 patients with hip prostheses were scored by 2 experienced nuclear medicine physicians to analyze clinical relevance. For all patients, a lesion was located in the field of view of the metal implant. Phantom and patients were scanned in a PET/CT scanner. The standard low-dose CT scans were processed with the iMAR algorithm. The PET data were reconstructed using attenuation correction provided by both standard CT and iMAR-processed CT. Results: For the phantom scans, cold artifacts were visible on the PET image. There was a 30% deficit in 18F-FDG concentration, which was restored by iMAR processing, indicating that metal artifacts on CT images induce quantification errors in PET data. The iMAR algorithm was useful for most patients. When iMAR was used, the confidence in interpretation increased or stayed the same, with an average improvement of 28% 6 20% (scored on a scale of 0%–100% confidence). The SUV increase or decrease depended on the type of metal artifact. The mean difference in absolute values of SUVmean of the lesions was 3.5% 6 3.3%. Conclusion: The iMAR algorithm increases the confidence of the interpretation of the PET/CT scan and influences the SUV. The added value of iMAR depends on the indication for the PET/CT scan, location and size/type of the prosthesis, and location and extent of the disease