New Generation of Resistant Sugar Beet Varieties for Advanced Integrated Management of Cercospora Leaf Spot in Central Europe

Abstract

Cercospora leaf spot (CLS) epidemics in sugar beet have been increasing in recent years causing higher use of fungicides. Concomitantly, the availability of effective fungicides is at risk because of resistance development in the fungus, the lack of new active ingredients as well as restrictive approval practices. A key option for an integrated management of CLS is cultivation of resistant varieties. Because of the yield penalty in resistant varieties, acceptance in commercial practice so far has been low. The aim of our study was to characterize recent sugar beet varieties registered in Germany in terms of resistance and tolerance to CLS and their value for integrated pest management. The genetic basis of CLS resistance in varieties is protected by intellectual property rights even after variety registration and not open to the public due to economic competition. To gain reliable data for cultivation, varieties have to be tested for their resistance traits under field conditions at varying levels of infection with Cercospora beticola. In collaboration with variety related stakeholders, 15 sugar beet varieties were tested in 49 field trials in Germany from 2014 to 2016 for their yield response to CLS. The trials were set up in a split-plot design with and without infection (i.e., with and without fungicide). The classification of varietal reaction to CLS is based on symptomatic leaf area (susceptibility) and the resulting relative yield loss (tolerance). Since the relation between both parameters varied among varieties, it was used as an additional parameter to describe tolerance. On this basis, three groups of varieties were identified. They can be characterized as a susceptible, a resistant and a presumably tolerant cluster. A comparison of the data with an older dataset originating from 2009 to 2011 revealed that yield performance of recent varieties with resistance to C. beticola caught up with susceptible varieties due to breeding progress. They showed no yield penalty in the absence of the disease and better economic performance than susceptible varieties. It is assumed that these varieties will allow a substantial reduction of fungicide use for an advanced integrated pest management under central European conditions.

Dynamics of cercospora leaf spot disease determined by aerial spore dispersal in artificially inoculated sugar beet fields

“…In line with these results, multiple resistances to fungicides with different modes of actions were also reported in other parts of Europe (Trkulja et al, 2017). In addition to fungicide application, the growth of sugar beet varieties with reduced susceptibility to C. beticola can support disease control (Varrelmann & Märländer, 2017;Vogel et al, 2018).…”

Cercospora beticola: The intoxicating lifestyle of the leaf spot pathogen of sugar beet

“…Inheritance of CLS resistance in sugar beet lines after introgression from wild sea beet is complex and has low heritability (Smith and Ruppel, 1974), while at the same time incorporation into high-yielding commercial sugar beet hybrids remains a challenge (Smith and Campbell, 1996). Promisingly, recent field trials in Germany showed that several European sugar beet varieties with CLS resistance lacked a yield penalty in the absence of disease and had better economic performance than susceptible varieties (Vogel et al, 2018). CLS resistance is typically managed by at least four identifiable quantitative trait loci (QTLs) (Smith and Gaskill, 1970;Nilsson et al, 1999;Setiawan et al, 2000;Taguchi et al, 2011).…”

New Proposals to Estimate Unbiased Selection Gain and Coefficient of Variation in Traits Evaluated Using Score Scales

“…; Wann et al, 2017); and disease severity in wheat (Iqbal et al, 2016;Saintenac et al, 2018), sugar beet (Beta vulgaris L.; Kakueinezhad et al, 2018;Vogel et al, 2018), common bean (Amaro et al, 2007), and coffee (Coffea arabica L.; Botelho et al, 2017). ; Wann et al, 2017); and disease severity in wheat (Iqbal et al, 2016;Saintenac et al, 2018), sugar beet (Beta vulgaris L.; Kakueinezhad et al, 2018;Vogel et al, 2018), common bean (Amaro et al, 2007), and coffee (Coffea arabica L.; Botelho et al, 2017).…”

“…L. ; Wann et al, 2017); and disease severity in wheat (Iqbal et al, 2016;Saintenac et al, 2018), sugar beet (Beta vulgaris L.; Kakueinezhad et al, 2018;Vogel et al, 2018), common bean (Amaro et al, 2007), and coffee (Coffea arabica L.; Botelho et al, 2017). Usually, these score scales are treated as interval scales.…”