A genetic study of mycelial compatibility groups of Sclerotium rolfsii

Abstract

Sclerotium rolfsii isolates from Texas peanut fields were grouped according to mycelial compatibility; 262 isolates arbitrarily-collected from plants showing symptoms of southern blight in four central Texas fields, and hyphal tipped, were examined for mycelial compatibility groups (MCG) based on the presence or absence of an antagonism zone (a clearing of mycelia) between paired colonies. These isolates could be placed in one of 12 MCG. MCG 6 was detected most frequently and was identified among isolates obtained from three widely separated fields. An additional seven MCG were identified in isolates collected from other locations in Texas. The internal transcribed spacer (ITS) region of the RDNA from several isolates belonging to different MCG was amplified by polymerase chain reaction (PCR) using the "Universal Primers" from ribosomal DNA. When amplification products of approximately 685 base pairs were digested with restriction endonuclease Mbo 1, four restriction digest patterns were observed. All isolates within an MCG consistently yielded the same restriction pattern and several MCG shared a common pattern. When a 18-base oligonucleotide primer, NK2, was used in PCR, three distinct amplification patterns were observed. Again, all isolates within a MCG had the same pattern and several MCG shared a common pattern.