MORPHOLOGICAL, CULTURAL, MOLECULAR, AND PATHOLOGICAL CHARACTERIZATION OFPHOMOPSIS SPECIES OCCURRING ON COTTON AND SOYBEAN

摘要

Phomopsis species were isolated from cotton and soybean tissues in the southeastern United States. Fungal isolations determinedPhomopsis longicolla and P. phaseolina colonized roots, petioles, leaves, and pod tissues of soybean, whereas a Phomopsissp. was isolated from roots, petioles, leaves, and boll tissues of cotton. Morphological and cultural differences werefound between the cotton Phomopsis isolates and the two soybean pathogens, P. phaseoli and P. longicolla. Toothpick inoculationsdetermined that all three species produced symptoms on cotton and soybean. Symptoms were more severe foreach species on the primary host. Restrictive fragment length polymorphism analyses of polymerase chain reaction (PCR)fragments were used to distinguish Phomopsis isolates from soybean and cotton. Specific primers were used to amplify a550 base pair sequence known as the Internal Transcribed Spacer (ITS) Region, a mitochondrial rRNA gene. PCR fragmentsfrom forty-nine Phomopsis isolates were sequenced. DNA sequence analyses displayed distinct variation between Phomopsisisolates from cotton and soybean. This is noteworthy because the naming of Phomopsis species thus far has been stronglybased on plant hosts.