Evaluation of resistance to Phomposis stem blight (caused by Diaporthe toxica) in Lupinus albus

Environmental effects and possible differences in pathogen race structure lead to some poor correlations of resistance ratings between different experiments (ranging from r = -0. 489 to 0. 800, depending on the experiment and tissue assessed). In field experiments consistent expression of the disease was dependent on rainfall. Screening in an irrigated disease nursery improved the methodology. Nevertheless, results suggest that it will be possible to develop new L. albus varieties that are resistant to Phomopsis stem blight should the disease become widespread in south-eastern Australia.Historically, in Australia, Phomopsis stem blight in Lupinus albus crops is rare. However, in 2004 an outbreak of this disease occurred in southern New South Wales affecting stems, pods and seeds of the cultivar Kiev-Mutant. This virulent outbreak represents a potential threat to the Australian lupin industry. The current research was therefore initiated to optimise disease screening protocols for evaluation of the disease. Screening for resistance to Phomopsis stem blight is important because stubble is a potential high source of inoculum in no-tillage systems, and grazing of Phomopsis infected stubble can cause lupinosis in stock animals. A single spore isolate of the fungal pathogen Diaporthe toxica collected from the 2004 outbreak was used to assess the levels of disease resistance in stem tissue in L. albus cultivars in some experiments and in other experiments field-infected stubble was used as inoculum. Resistance of current L. albus cultivars, breeding lines, and landraces to D. toxica was assessed in both glasshouse and field experiments in 2007 and 2008. The results showed that resistance existed in some cultivars and several germplasm accessions.