2 GENETICALLY DISTINCT POPULATIONS OF COLLETOTRICHUM-GLOEOSPORIOIDES FROM CITRUS

Two or more types of Colletotrichum gloeosporioides from citrus have been described on the basis of colony morphology and growth in culture. We report here two distinct genetic populations of the fungus from sweet orange (Citrus sinensis) and Tahiti lime (Citrus aurantifolia); the distinction of the two populations was made on the basis of DNA variation at several genetic loci as well as cultural morphology and growth. Type 1 strains are slow growing, morphologically stable, and contain a single homogeneous form of ribosomal DNA (rDNA) as detected by common HindIII, PstI, SphI, and SstI fragments hybridizing to cloned Neurospora crassa rDNA. Type 2 strains are faster growing, morphologically less stable, and have rDNA repeats distinct from type 1 strains. The rDNA from a type 1 strain was cloned and mapped for 10 restriction enzyme sites and genes coding for large subunit, small subunit, and 5.8S rRNA. A subclone constructed from the nontranscribed spacer region of this rDNA clone hybridizes only to rDNA from type 1 strains. DNA polymorphisms detected by heterologous hybridization with cloned N. crassa genes for glutamate dehydrogenase, anthranilate synthetase, histidinol dehydrogenase, and beta-tubulin corresponded to type 1 or 2 strains. Chromosome-sized DNAs separated by pulsed-field gel electrophoresis also corresponded to type 1 and type 2 strains defined by restriction fragment length polymorphism. Type 1 strains had five large chromosomal DNAs: 7.6, 7.0. 4.7. 3.7, and 3.3 (or 2.8) million base pairs (Mb) and one or two smaller chromosomes ranging in size from 1.6 to 0.63 Mb. Type 2 strains had three large chromosomal DNAs (7.8, 4.7, and 3.7 Mb) and two to four smaller chromosomal DNAs ranging in size from 0.52 to 0.28 Mb. Type 1 strains all were more tolerant to benomyl than type 2 strains. For every genetic marker examined, polymorphism that corresponded to morphological type was observed.