Bacterial leaf and stem spot (Xanthomonas alfalfae) of lucerne in Queensland

Abstract

A bacterial leaf and stem spot of lucerne (Medicago sativa cv. Hunter River) was recorded from four districts in Queensland. The pathogen was identified as Xanthomonas alfalfae but comparative pathogenicity tests with X. phaseoli, showed that X. alfalfae would be more correctly placed as a forma specialis of X. phaseoli. The susceptibility of sixteen cultivars and lines of lucerne were considered, and four cultivars, Hunter River, Moapa, Siro Peruvian and Paravivo exhibited a degree of resistance to the disease. This is the first recording of X. alfalfae in Australia.