MATING-TYPE, PATHOTYPE AND RAPDS ANALYSIS IN DIDYMELLA-RABIEI, THE AGENT OF ASCOCHYTA BLIGHT OF CHICKPEA

Eleven pathotype groups (A-K), including five not previously reported, of Didymella rabiei (anamorph Ascochyta rabiei), representing isolate s of the pathogen from Ascochyta blight-affected chickpeas mainly from India, Pakistan, Spain and the USA, were characterized using 44 singl e-spore isolates tested against seven differential chickpea lines. Of 48 isolates tested for mating type, 58% belonged to MAT 1-1 and 42% to MAT 1-2. Thirty-nine D. rabiei isolates, as well as two isolates of A scochyta pisi and six isolates of unrelated fungi, were analyzed using Randomly Amplified Polymorphic DNAs (RAPDs) employing five primers (P 2 at 40 degrees C, and OPA3, OPC1, OPC11 and OPC20 at 35 degrees C). C omputer cluster analysis (UPGMA / NTSYS-PC) detected a relatively low level of polymorphism among all the D. rabiei isolates, although at ca 7% dissimilarity, ca 10 RAPD groups [I-X] were demarcated, as well as subclustering within the larger groups. By the same criteria, the max imum dissimilarity for the whole population of D. rabiei isolates was cc; 13%. No correlation was found between different RAPD groups, patho type, or mating type of D. rabiei, although some evidence of clusterin g based on geographic origin was detected. The use of RAPDs enabled us to identify specific DNA fragments that may have a potential use as g enetic markers in sexual crosses, but none which could be used as viru lence markers.