Observations on the Physiological Races of Colletotrichum lagenarium

Abstract

1. The differential hosts that were recommended for distinguishing the three physiological races of Colletotrichum lagenarium (Pass.) Ell. & Halst. (2) did not give the reported disease reactions but did permit each race to be identified. 2. A survey of twenty varieties of watermelon, muskmelon, cucumber, Cucurbita moschata, and C. maxima revealed that the Chris Cross watermelon variety could be used as an additional differential host to identify the three races of the pathogen. 3. Five isolates of anthracnose were studied, using Black Diamond, Charleston Gray, and Chris Cross watermelon varieties and Model and PI 163213 cucumbers as differential hosts. Four races were identified, Race 4 being described for the first time. 4. Study of progenies of the crosses involving watermelon varieties that were either resistant or susceptible to Race 3 confirmed the previous report (3) that resistance is controlled by a single dominant gene. No watermelon variety was resistant to Race 2, and neither were the hybrids among these varieties.