Evidence thatDiaporthe toxicainfection ofLupinus albusis an emerging concern for the Australian lupin industry

Abstract

Lupinus albus has been grown commercially in Australia since the 1970s and has long been regarded as resistant to phomopsis caused by Diaporthe toxica. Isolates capable of infecting L. albus were collected following an outbreak of phomopsis in 2004 in southern New South Wales. Glasshouse screening of L. albus cultivars with the pathogen revealed that genotypes differ in their response to D. toxica with some current cultivars having useful resistances. Several breeding lines and old cultivars were susceptible in either vegetative or reproductive tissue or both. The commonly grown commercial cultivar Kiev Mutant was moderately susceptible in all tissues assessed. A principle component analysis gave weak to moderate correlation (r = 0.14 to r = 0.54, depending on the two-way comparison) between vegetative and reproductive tissue, which is suggestive that resistance in different tissues may be under distinct genetic control. The germination of infected seed from the outbreak in 2004 was severely compromised, and much of the seed harboured the pathogen. A survey of 171 commercial seed samples from 2004 to 2006 showed that phomopsis discoloured seed was present in only 20 samples, all of them confined to southern New South Wales. While the pathogen presents a risk to L. albus cropping zones in southern New South Wales, it is not widely spread at this stage. However, vigilance is required to prevent infected seed from being sown so that the disease can be kept in check.