Colletotrichum acutatum J. H. Simmonds is an important pathogen with a worldwide distribution and is involved in diseases and disease complexes of a number of economically important hosts (2). Three taxa, namely C. acutatum, C. gloeosporioides (Penz.) Penz. & Sacc. in Penz. (self-sterile/heterothallic isolates), and Glomerella cingulata (Stoneman) Spaulding & H. Schrenk (self-fertile/homothallic isolates), are involved in bitter rot disease of apple in the southeastern U.S. The three species can be distinguished based on morphological criteria, growth rates, and mtDNA restriction fragment length polymorphisms (RFLPs) (1,3). In studies of sexual compatibility, isolates of C. acutatum from apple readily produced perithecia in artificial culture on a minimal agar salts medium under continuous light when mated with isolates of C. acutatum that belonged to different vegetative compatibility groups. Sexual recombination between parental isolates was confirmed by examination of the segregation of genetic markers (nitrate nonutilizing [nit] mutants, sulfate nonutilizing [sul] mutants, and chromogenic pigmentation) among randomly collected ascospore progeny. No perithecia were observed when isolates of C. acutatum were crossed with homothallic isolates of G. cingulata or heterothallic isolates of C. gloeosporioides. Several isolates of C. acutatum from apple and one from blueberry that produced perithecia in mating studies had an identical or very similar mtDNA RFLP haplotype. Efforts are underway to characterize the teleomorphic form of C. acutatum. References: (1) J. C. Correll et al. Phytopathology 83:1412, 1993. (2) P. R. Johnston and D. Jones. Mycologia 89:420, 1997. (3) Y. Shi et al. Plant Dis. 80:692, 1996.