Preamble: Anthracnose, caused by Colletotrichum lindemuthianum is a serious seed borne pathogen of common bean. It is a highly variable pathogen with a large number of pathogenic races that have been characterized on the 12-member differential host series shown on table 1 (Padder et al. 2017; Melotto et al. 2000). The race structure of C. lindemuthianum isolates characterized by Balardin et al (1997) over a large number of Latin and North American countries illustrates the widespread occurrence of certain races (race 73) in many countries and the unique occurrence of others found only in single locations. The race structure also follows the gene pool specificity of the host genotypes from which the race was isolated. In 2017, a new race 109 was detected in commercial bean fields in Michigan.
Leaf and Pod lesions of anthracnose on susceptible bean cultivars
Seventeen independent loci, Co-1 to Co-17, conditioning resistance have been mapped to the eight chromosomes Pv01, Pv02, Pv03, Pv04, Pv07, Pv08, Pv09 and Pv11 in addition to seven other genes Co-u, Co-w, Co-x, Co-y, Co-z, CoPv02c and CoPv09c, some of which have been mapped to the same chromosomes where the numbered loci are located (Ferreira et al., 2013). Anthracnose resistance is dominant at all loci except the co-8 locus, and multiple alleles have been identified at the Co-1, Co-3, Co-4, and Co-5 loci. Resistance genes are arranged as gene clusters chiefly as Coiled-Coil-Nucleotide-Binding-Site-Leucine-Rich-Repeat (CNL) regions and many co-localize with genes conditioning resistance to other pathogens such as bean rust. Breakdown of resistance is common, requiring breeders to develop gene pyramids to stabilize resistance using linked markers to facilitate effective gene deployment in multigenic pyramids.
Table 1. Anthracnose differential series, resistance genes, host gene pool, and the binary number of each cultivar used to characterize races of anthracnose in common bean. (April, 2011)
|Differential Cultivar||Host Genes||Gene Pool1||Binary Number2|
|PI 207262||Co-43, Co-33||MA||128|
|AB 136||Co-6, co-8||MA||1024|
|G 2333||Co-42, Co-52, Co-7||MA||2048|
1 MA: Middle American gene pool; A: Andean gene pool of Phaseolus vulgaris
2 Binary number: 2n, n is equivalent to the place of the cultivar within the series. The sum of cultivars with susceptible reactions will give the binary number of a specific race. For example race 17 is virulent on Michelite  + Widusa .
Balardin, R.S., A.M. Jarosz, and J.D. Kelly. 1997. Virulence and molecular diversity in Colletotrichum lindemuthianumfrom South, Central and North America. Phytopathology 87:1184-1191.
Ferreira, J.J., A. Campa, and J.D. Kelly. 2013. Organization of Genes Conferring Resistance to Anthracnose in Common Bean. In: Translational Genomics for Crop Breeding: Biotic Stress, Volume 1: 151-181. Editors: Roberto Tuberosa and Rajeev Varshney, Wiley-Blackwell Pubs.
Melotto, M., R.S. Balardin and J.D. Kelly. 2000. Host-pathogen interaction and variability of Colletotrichum lindemuthianum. Pp 346-361. In: ColletotrichumHost Specificity, Pathology, and Host-Pathogen Interaction. Editors: D. Prusky, S. Freeman, and M.B. Dickman, APS press St. Paul, MN.
Padder, B.A., P.N. Sharma, H.E. Awale, and J.D. Kelly. 2017. Colletotrichum lindemuthianum, the causal agent of bean anthracnose. J. Plant Pathology 99: 317-330. doi: 10.4454/jpp.v99i2.3867