Identification of resistance sources and characterization of resistance factors in Brassica species to Verticillium longisporum

Abstract

Chapter 1: Introduction Aims and objectives of the studyOilseed rape (Brassica napus L. oleifera) is at present the most important oilseed crop in Europe. The cultivation area in Germany was more than 1.5 M ha in 2007 (Federal Statistical Office, Germany, 2007; EUROSTAT, 2007). As a result of the increasing area under rapeseed cultivation and the relatively high crop rotation rate disease problems have become a major issue in current breeding efforts.Verticillium wilt caused by the hemibiotrophic pathogen Verticillium longisporum (ex. V. dahliae var. longisporum Stark; comb. nov. Karapapa) is one of the principal diseases in the cultivation of oilseed rape, besides blackleg and stem canker caused by Phoma lingam and stem rot caused by Sclerotinia sclerotiorum. Soil inoculum in form of microsclerotia can gain densities that lead to a disease incidence of up to 100% (Zeise & Steinbach, 2004) in heavily infested fields. The control of these resting structures is particularly difficult because they can survive in the soil for several years (Schnathorst, 1981;. Due to the fact that chemical treatments have no effect on the occurrence of V. longisporum, the implementation of cultural practices such as crop rotation, time point of sowing, choice of intercrops and the use of resistant cultivars within an integrated disease management approach is the most promising strategy of controlling Verticillium wilt. Unfortunately, until now, breeding for resistance for both winter and spring type oilseed rape has been severely hampered by the absence of sufficient resistance in commercially available breeding material, however, recently, some promising genotypes of cabbage (B. oleracea) and turnip rape (B. rapa) with enhanced resistance were identified (Happstadius et al., 2003;Dixelius et al., 2005). In addition, oilseed rape cultivars with partial resistance also have the potential to reduce crop losses in an environmentally safe, cost-effective manner. Moreover, these cultivars can be combined with other control measurements to achieve optimal levels of disease management (Debode, 2005). Thus, in order to preserve the productivity of the intensive oilseed rape cropping areas in a sustainable, environment-friendly manner, the most promising approach to control Verticillium wilt of oilseed rape is to improve the resistance of the cultivars currently available. This work describes results from a joint project conducted in collaboration with the Institute of Plant Breeding of the Justus-Liebig-University of Giessen and the Association of German Plant Breeders e.V. (GFP) with the ultimate goal of improving the resistance of commercial cultivars to Verticillium. pursued throughout this project: In the first approach, the interaction of the host-specific species V. longisporum (compatible interaction) with B. napus was compared with the nonhost interaction of B. napus with V. dahliae. The differential interactions of V. longisporum and V. dahliae on the root surface and in the root and shoot vascular system of B. napus were studied ...

Bioproducts and their potential in protection of Brassica napus L. against Verticillium longisporum

“…Early symptoms can be discolourations of stems, such as brownish stripes on one side along the stem, and later microsclerotia becomes visible beneath the epidermis, in the pith and the root tissue (Knüfer 2011). Oilseed rape responds to pathogen invasion with the formation of vascular occlusions, which affect water transport in the plant (Eynck 2008).…”