EVIDENCE FOR THE EXISTENCE OF 2 SUBPOPULATIONS IN PHYTOPHTHORA-CAPSICI AND A REDESCRIPTION OF THE SPECIES

Morphological, physiological and isozyme data were obtained for 113 is olates of P. capsici. Isozyme analysis of 18 loci from 15 enzymes reve aled two distinct subgroups, CapA and CapB. Both subgroups contained i solates from widely distributed geographical locations and from a rang e of hosts. There was considerable morphological and physiological div ersity amongst the isolates, but also significant differences between the two isozyme subgroups. The majority of isolates in CapA possessed rounded sporangia and exhibited irregular sporangial ontogeny. Most Ca pB isolates produced ellipsoid-lanceolate sporangia and ca 50% had an umbellate ontogeny. Chlamydospore-forming isolates occurred exclusivel y in the CapB subpopulation. A minority of CapA or CapB isolates exhib ited sporangial traits more typical of the other isozyme subgroup. Con sequently, use of morphological characters alone would not always allo w correct assignment of an isolate to its isozyme subgroup. Phytophtho ra capsici is re-defined based on the wide variation in characters fou nd in this worldwide population sample. A single available isolate of P. mexicana was placed in isozyme subgroup CapA, though it differed mo rphologically from the P. capsici isolates in producing non-caducous s porangia.