A Decade of Variety Testing for Resistance of Red Clover to Southern Anthracnose ( Colletotrichum trifolii Bain et Essary) at the Bavarian State Research Center for Agriculture (LfL)

Southern anthracnose is caused by the fungal pathogen Colletotrichum trifolii Bain et Essary and affects red clover ( Trifolium pratense ) cultivation, causing severe losses in plant stands. Artificial inoculation with the pathogen in the greenhouse has been proven to effectively differentiate varieties for their resistance based on the survival rates of plants. Additionally, this method was successfully used to improve red clover populations via recurrent selection. However, not much is yet known on its association with resistance behavior in the field. In this study, results from 10 years of artificial inoculation trials at the Bavarian State Research Center for Agriculture were analyzed and compared to official German variety descriptions that are based on field data. A good congruency between survival rates from the greenhouse and official susceptibility ratings were observed. Thus, data from greenhouse tests have great potential to complement official variety lists where gaps exist. It was shown that within only three generations of recurrent selection using the greenhouse test, an existing variety could be significantly improved in terms of its resistance to Southern anthracnose without changing its DUS characteristics. A continuously increasing resistance level in the varieties registered in Germany since 2005 indicates that breeders can successfully respond to the threat imposed by this relatively new disease.