Random Amplified Polymorphic DNA and Polymerase Chain Reaction Markers for the Differentiation and Detection of Stenocarpella maydis in Maize Seeds

The genetic relationship of 34 isolates of Stenocarpella maydis from di€erent geographic regions in South Africa was analysed by random ampli®ed polymorphic DNA (RAPD) and ribosomal DNA markers. Two genetic groups were di€erentiated by using three RAPD primers and correlated to the cultural morphol- ogy of the isolates. Of all the isolates tested, 79.4% were clustered into RAPD group I (RG I), which did not sporulate when cultured on potato dextrose agar (PDA) at 25 C for 10 days. The rest of the isolates designated as RG II sporulated on PDA medium and showed a higher genetic variation. Ribosomal DNA (rDNA) was ampli®ed using polymerase chain reaction (PCR) with the universal primers, internal transcribed spacer (ITS) 1 and ITS 4. Restriction digestion of PCR products displayed three types (RF A, RF B and RF C) of pro®les. RF A was in accordance with RG I. RF B was consistent with RG II except for one isolate, U5. However, U5 displayed a unique pro®le and had no restriction sites for Hpa II and Hae III. The results indicate that two distinct genetic groups exist among S. maydis isolates from maize in S. Africa. The ITS1 and ITS2 regions of rDNA were sequenced and primers were designed. The designed primer pair P1/P2 per- mitted a sensitive and speci®c detection of S. maydi