AN INTEGRATED STUDY OF MORPHOLOGICAL AND ISOZYME PATTERNS FOUND WITHIN A WORLDWIDE COLLECTION OF PHYTOPHTHORA-CITROPHTHORA AND A REDESCRIPTION OF THE SPECIES

A worldwide collection of 77 isolates of Phytophthora citrophthora fro m 30 different host species was investigated for variation in morpholo gy and isozyme patterns. All isolates produced non-caducous, papillate sporangia. Only those isolated from cacao (Theobroma cacao) in Brazil produced chlamydospores, whereas cacao isolates from Indonesia did no t produce chlamydospores. Over 70% of the isolates were sterile; the r emainder could be designated as the Az mating type based on pairings w ith P. capsici, though P. citrophthora itself did not produce oospores . The species was separated into three distinct isozyme subgroups: CTR 1 containing isolates from widely distributed geographical locations o n a broad range of hosts, CTR2 composed exclusively of Brazilian isola tes from cacao, and a new subgroup CTR3 consisting of Indonesian isola tes also isolated from cacao. A total of 14 enzymes and 17 putative lo ci were used to compare the isolates and seven loci were polymorphic. Peptidase was diagnostic for CTR1, malate dehydrogenase (MDH1) for CTR 2 while the migration patterns for both glucose-6-phosphate dehydrogen ase and hexokinase (HEX2) differentiated CTR3. A redescription of R. c itrophthora is presented based on all 77 isolates including physiologi cal, morphological and isozyme characters that can assist identificati on.