Rotklee ist als essentielles Fruchtfolgeglied speziell im ökologischen Landbau unentbehrlich. Resistente Sorten wären im Falle einer Ausbreitung der Pilzkrankheit Anthracnose von zentraler Bedeutung

Hartmann, Stephan

Jacob, Irene

Schubiger, Franz Xaver

Struck, Christine

English

Organic Eprints

Genetic diversity of red clover varieties listed in Germany concerning the resistance to Southern Anthracnose Jacob I.1, Hartmann S.1, Schubiger F.X.2 and Struck C.31Institute of Crop Husbandry and Plant Breeding (IPZ) of the Bavarian State Research Centre for Agriculture (LfL), Am Gereuth 8, 85354 Freising, Germany2 Agroscope Reckenholz-Tänikon (ART), Reckenholzstrasse 191, 8046 Zürich, Switzerland  3 University of Rostock, Faculty of Agricultural and Environmental Sciences, Institute for Land Use, Crop Health, Satower Str. 48, 18059 Rostock, Germany Corresponding author: irene.jacob@lfl.bayern.de AbstractRecently, there has been evidence both from testing sites and agriculturally used fields concerning the appearance of Colletotrichum trifolii Bain et Essary, causing Southern Anthracnose in red clover and red clover pasture stands. This disease is able to cause large losses in yield. The aim of this investigation was to evaluate all red clover cultivars listed in Germany (in 2009) with regard to their resistance against the pathogen. One foreign genotype ‘Starfire’, bred in the USA and known to be highly resistant to Southern Anthracnose, was also incorporated into this research. A ranking of the cultivars could be generated based on a test for resistance performed in the greenhouse. The resistance of the cultivars was expressed as a percentage of plant survival seven weeks after inoculation. Results showed a wide range in quantitative resistance characteristics towards Colletotrichum trifolii from 29 to 87% survival. Hence the evaluated genotypes can be classified into resistant to susceptible forms. Another important finding was that among the screened varieties diploid cultivars overall seemed to be more resistant than tetraploid genotypes.Keywords: Colletotrichum trifolii, red clover, Southern Anthracnose, Trifolium pratense,varietyIntroduction Red clover (Trifolium pratense L.) is an essential element in crop rotations, especially for organic farming. In recent years, it became more obvious that there were failures of red clover plants in the field because of ‘Southern Anthracnose’, a disease caused by the fungus Colletotrichum trifolii Bain et Essary.This seed-borne pathogen is known to cause aggressive damage in red clover fields. Typical symptoms are stem lesions resulting in a bending of the stem in the upper zone of the plant. The fungus spreads out via conidia preferentially under warm and moist weather conditions. At the beginning of 2009, twenty-eight cultivars of Trifolium pratense were listed in Germany. This research was intended to find out if there are differences in resistance to C.trifolii among the red clover cultivars listed in Germany and to identify sources of resistance for further breeding. Materials and methods To classify these listed genotypes according to their level of susceptibility against C. trifolii, a test for resistance as stated by Schubiger et al. (2003) was performed in the greenhouse under controlled conditions in 2008 and 2009. For that purpose, germinated grains were planted into Quickpots™. The spatial arrangement was totally randomized. The plants were cut five weeks after planting. Two weeks later, they were inoculated with a conidia suspension (spore density Grassland Science in Europe, Vol. 15 3443 x 106 spores ml-1; inoculum provided by ART Zürich). Subsequently, the plants were covered with a PVC-tent for incubation for six days. Plants were cut two and six weeks after inoculation and after one week of regrowth (seven weeks after inoculation) the number of dead plants was determined. After having converted the data with the arcsin square root transformation, analysis of variance was performed with the SAS program. The Student-Newman-Keuls Test was used to identify significant differences among genotypes.  Results and discussion The tested genotypes showed a clear differentiation in terms of susceptibility against the pathogen. The number of survived plants varied over a wide range (Table 1).Table 1. Ranking of the tested cultivars concerning their resistance against Colletotrichum trifolii based on a biennial test in the greenhouse. Same letters mark non-significant differences, P = 0.05 (Student-Newman-Keuls Test). Genotype  Level of ploidy  Plant survival [%] Starfire 2n 87 a Pavo 2n 79  bMerula  2n 69  c Elanus  4n 66  cd Global  2n 65  cde Lemmon  2n 64  cde Harmonie  2n 60  cdef Odenwaelder Rotklee  2n 59  cdef Larus  4n 57  cdefg Regent  2n 54   defgh Astur  4n 54   defgh Milvus  2n 53   defgh Nemaro  2n 53   defgh Pirat  2n 50   defgh Montana  2n 50    efghi Rotra  4n 48     fghij Temara  4n 47     fghijk Diplomat  2n 47     fghijk Heges Hohenheimer  2n 47     fghijk Tempus  4n 41      ghijkl Wiro  2n 39       hijkl Lucrum  2n 38       hijkl Taifun 4n 35         ijkl Maro 4n 35         ijkl Atlantis  4n 35         ijkl Titus 4n 35           jkl Amos  4n 34           jkl Mars 4n 31            kl Kvarta  4n 29              l As expected, the American cultivar ‘Starfire’ showed the highest level of resistance (87% plant survival). Among the varieties listed in Germany, ‘Pavo’ showed the best level of resistance, the percentage of surviving plants was 79% on average. The most susceptible cultivar tested was ‘Kvarta’ with a plant survival rate of 29% only. The two varieties with the highest level of resistance among the cultivars listed in Germany, ‘Pavo’ and ‘Merula’, were bred in areas where C. trifolii was present (Boller et al., 1998; Schubiger et al., 2003). Grassland in a Changing World 345A correlation between plant survival and year of listing can be excluded. Among the screened cultivars in this investigation, diploid genotypes appeared to have a higher rate of plant survival than tetraploid ones. The improvement of resistance occurs earlier in the diploid varieties because of the breeding process performed in praxis, as preselected diploid genotypes are in most cases base material in breeding tetraploid red clover (Boller et al.,2010). In surveys by Schubiger et al. (2003) the best ranked varieties were also diploid.ConclusionThe results demonstrated that there were differences in resistance to the fungus C. trifoliiamong red clover cultivars listed in Germany. Although the greenhouse data have to be verified in field tests, it seems to be already possible to identify sources of resistance for further breeding. ReferencesBoller B., Schubiger F.X. and Kölliker R. (2010) Red clover. In: Boller B., Posselt U.K. and Veronesi F. (eds.) Fodder Crops and Amenity Grasses. Handbook of Plant Breeding 5, Springer, New York, 439-455. Boller B., Bigler P., Bucanovic I. and Bänziger I. (1998) Southern Anthracnose – a new threat for red clover persistence in cooler regions? In: Boller B. and Stadelmann F.J. (eds.) Breeding for a Multifunctional Agriculture. 21st Meeting, Fodder Crops and Amenity Grasses Section of EUCARPIA, Switzerland, 195-198.  Schubiger F.X., Streckeisen P. and Boller B. (2003) Resistance to Southern Anthracnose (Colletotrichum trifolii)in cultivars of red clover (Trifolium pratense). Czech Journal of Genetics and Plant Breeding 39 (Special Issue), 309-312. Grassland Science in Europe, Vol. 15 346

Genetic diversity of red clover varieties listed in Germany concerning the resistance to Southern Anthracnose

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