Characterization of Sphaeropsis sapinea isolates from South Africa, Mexico, and Indonesia

Post-hail-associated dieback of Pinus patula and P. radiata trees, induced by Sphaeropsis sapinea (=Diplodia pinea), is a common and important disease in commercial pine plantations. Two morphotypes, A and B, have been descri bed for this fungus based on differences in cultural characteristics, conid ial morphology, and virulence among isolates from the north central United States. The existence of the two described morphotypes was later verified t hrough the use of random amplified polymorphic DNA (RAPD) analyses, and the morphotypes were designated as the A and B RAPD marker groups. The objecti ve of this study was to characterize a set of S. sapinea isolates from Sout h Africa, Indonesia, and Mexico using RAPD analysis and DNA sequencing of t he internal transcribed spacer (ITS) region of the ribosomal DNA operon. Si zes of conidia and culture morphology were, furthermore, used to compare th e three groups of S. sapinea isolates that emerged from the RAPD analysis. Two of the RAPD groups included isolates from the United States, representi ng the A and B morphotypes, while the third RAPD group accommodated Indones ian and one Mexican isolate. ITS sequences of all the S. sapinea isolates w ere highly homologous and resolved only the A and B RAPD groups. The ITS se quences of the isolates in the third RAPD group were the same as those of t he A RAPD group. Conidia of isolates representing the A and B morphotypes w ere approximately the same size, but those of the third RAPD group were sig nificantly longer. RAPD analysis enabled us to identify a third group of S. sapinea that is different from the well-recognized A and B groups. Isolate s in this third RAPD group also have a distinct morphological characteristi c and thus represent a third discrete morphological group, which we refer t o as the C morphotype of S. sapinea.