Journal of Plant Pathology Archive

Abstract:

The species composition of a total of 400 single-ascospore Leptosphaeria isolates from winter oilseed rape collected in 2006-2009 in Lithuania was studied by cultural characteristics and molecular techniques. In general, 70.3% of the tested isolates belonged to Leptosphaeria maculans and 29.7% were attributed to L. biglobosa due to differences in cultural characteristics and following species-specific PCR analysis. Both techniques consistently identified the presence of L. maculans only in the 2006 and 2007 collections, whereas both species were detected in 2008 and 2009, with prevalence of L. biglobosa in 2008 (89% of tested isolates), and of L. maculans in 2009 (57% of tested isolates). The equal distribution according to mating types and the high degree of genetic variation among L. maculans isolates as detected by AFLP markers, suggests sexual reproduction. Whereas phoma leaf spot incidence on winter oilseed rape was 28-48% 90 days after sowing in 2004-2006, increasing to 43-62% 30 days later, phoma canker infection rates at the stem base were 72, 48 and 58% at harvest in 2005, 2006 and 2007, respectively. The presence and prevalence of L. maculans in Lithuania supports the assumption of eastward spreading of this fungus in Europe and suggests that there is a high risk of severe phoma stem canker epidemics in this country.