Variation among Colletotrichum isolates from diseased coffee berries in Ethiopia

Abstract

Variation of a representative range of Colletotrichum isolates from diseased coffee berries, sampled from various regions in Ethiopia, was studied using morphological and pathological criteria. Spore suspensions from 4-week-old cultures of five isolates were applied to 8-week old seedlings, grown from known susceptible coffee cultivars, by wrapping strips of absorbent cotton wool dipped in inoculum around the seedlings. Substrate utilization of citrate and tartrate was assessed in stationary liquid. Morphological characters and conidial size were recorded. Random amplification of genomic DNA was done by PCR using 10 base primers. The seedling hypocotyl test confirmed variation in aggressiveness between the various isolates while biochemical tests and cultural characters showed that this was related to the occurrence of both Colletotrichum gloeosporioides and Colletotrichum kahawae in the range of isolates tested. PCR showed similar trends in the nucleotide sequence and did not differentiate between the isolates. The study showed that both C. kahawae and C. gloeosporioides occur in diseased berries, probably as sequential colonizers of diseased tissues.