Selection in Red Clover for Resistance to Northern Anthracnose

Northern anthracnose (NA), caused by Kabatiella caulivora (Kirchn.) Karak., is a destructive disease of red clover ( Trifolium pratense L.) in the northern USA. The range of adaptation of southern red clover cultivars could be broadened by addition of NA resistance. A program was initiated to enhance NA resistance in 10 parental populations related to the cultivar Kenstar, and to evaluate response to phenotypic recurrent selection in these low NA‐variation susceptible populations. These populations are resistant to powdery mildew ( Erisyphe polygoni DC) and bean yellow mosaic virus strain 204‐1. The 10 populations were subjected in a greenhouse to six cycles of phenotypic recurrent selection for NA resistance. Remnant seed from each cycle of selection was used to establish an evaluation study. Northern anthracnose resistance was significantly improved. Mean disease severity index (DSI) was reduced by 36% through six cycles and was linear across cycles. However, populations were variable in their response to selection. Selection improved DSI by less than 24% through six cycles in four of the populations, while average improvement of the other six was 46%. Realized heritabilities averaged 20% per cycle and were greatest among the six populations with greatest improvement in DSI Inbreeding was minimal during the selection process, averaging 2.8% after six cycles. The resistance obtained from these low‐variation susceptible populations indicates that phenotypic recurrent selection is an effective means of uncovering latent variation for resistance to NA.