Semiselective Medium forColletotrichum gloeosporioidesand Occurrence of ThreeColletotrichumspp. on Pepper Plants

Abstract

Inhibition of mycelial growth of Colletotrichum capsici and C. gloeosporioides was significantly (P = 0.01) less than that of Alternaria sp. and Fusarium spp. when grown on a semiselective medium, C. gloeosporioides pepper isolate medium (CGPIM) containing one-quarter strength potato-dextrose agar amended with fenarimol and vinclozolin at 5 micrograms/ml each, chloramphenicol and erythromycin at 6.5 micrograms/ml each, iprodione at 15 micrograms/ml, neomycin sulfate at 20 micrograms/ml, and tetracycline hydrochloride at 25 micrograms/ml. Fenarimol enhanced the detection of C. gloeosporioides as cream-yellow sporulating colonies formed around infected and/or infested pepper (Capsicum spp.) seeds. When pepper seeds were placed on CGPIM and wet filter paper, C. capsici occurred at equal frequencies, but the frequency of C. gloeosporioides was significantly (P = 0.01) higher on CGPIM than on wet filter paper. C. capsici was detected on 14.5% of the seeds from var. LSU Sport, while C. gloeosporioides detection was less frequent. C. gloeosporioides was isolated from 30 and 1% of diseased fruits harvested and stored for 130 and 225 days, respectively. CGPIM and wet filter paper were equally effective in evaluating the occurrence of C. capsici but the occurrence of C. gloeosporioides and Glomerella cingulata appressoria was significantly (P = 0.01) higher on CGPIM than on wet filter paper. C. capsici was recovered more frequently than either C. gloeosporioides or G. cingulata on inoculated leaves.