Conidial anastomosis tubes in Colletotrichum Maria Gabriela Roca, a,b Lisete C. Davide, a Maria Cristina Mendes-Costa, a and Alan Wheals b, * a Department of Biology, Universidade Federal de Lavras (UFLA), Lavras, 37-200 000 MG, Brazil b Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK Received 7 March 2003; accepted 24 June 2003 Abstract We describe the occurrence of special kinds of hyphae that create anastomoses directly between conidia. They can be found both in the laboratory and on infected plants. They first appear within asexual fruiting bodies approximately 15 days after conidiation has begun leading to the appearance of chains of connected conidia. Coincident with this we demonstrate in Colletotrichum lindemu- thianum nuclear dynamics, including fragmentation, with cytoplasmic flow and passage of nuclei and organelles between conidia through the anastomosis tubes. We propose that conidial anastomosis tubes play an important role in the life cycle of these fungi. Ó 2003 Elsevier Inc. All rights reserved. Keywords: Colletotrichum lindemuthianum; Colletotrichum gossypii; Colletotrichum gloeosporioides; Fungal cell; Cytogenetics; Micronuclei; Microscopy; Mitochondria; Vacuoles 1. Introduction Colletotrichum species cause anthracnose on a wide range of plants from both temperate and tropical envi- ronments (Bailey et al., 1992): Colletotrichum lindemu- thianum produces damage on the stems, leaves, and fruit of the common bean, Phaseolus vulgaris (Perfect et al., 1999; Rava and Sartorato, 1994), Colletotrichum gos- sypii infects cotton plants (Waller, 1992) and Colleto- trichum gloeosporioides attacks a wide range of hosts. Many Colletotrichum species have no sexual (teleomor- phic) states and are consequently considered to be asexual when they infect plants in the field. The great variability shown by Colletotrichum strains including chromosomal polymorphisms (Brooker et al., 1991; Kistler and Miao, 1992; OÕSullivan et al., 1998; Roca et al., 2003; Rodriguez and Redman, 1992) suggests a requirement for a genetic recombination mechanisms other than simply mutation and consequential hetero- karyosis (Hastie, 1981). Hyphal anastomoses that per- mit cytoplasmic connections and nuclear exchange in filamentous fungi can occur in the laboratory but it is not clear if they occur in nature (Glass et al., 2000; Zeigler, 1998). Maturing fungal colonies of C. lindemuthianum readily produce asexual fruiting bodies (acervuli) that produce spores (conidia) that develop as terminal cells on spore-bearing structures. The conidia are marked with a birth scar and are uninucleate when the spores are released but they are retained within the confines of the asexual fruiting body (Brown and Brotzman, 1979). Inhibitors in the mucilaginous matrix prevent germina- tion of the conidia in some Colletotrichum species (Nicholson, 1992). We report the appearance of conidial anastomoses tubes (CATs) after the onset of conidia- tion in three Colletotrichum species and describe for C. lindemuthianum the cytology of these structures through which there is passage of cytoplasm containing mitochondria, vacuoles, and nuclei. 2. Material and methods 2.1. Strains and culture conditions Fifteen characterised strains of C. lindemuthianum were studied (Table 1) as well as C. gossypii (isolated Fungal Genetics and Biology 40 (2003) 138–145 www.elsevier.com/locate/yfgbi * Corresponding author. Fax: +44-1225-386779. E-mail address: bssaew@bath.ac.uk (A. Wheals). 1087-1845/$ - see front matter Ó 2003 Elsevier Inc. All rights reserved. doi:10.1016/S1087-1845(03)00088-4