The monophyletic origin of host-specific taxa in the plant-pathogenic Fusarium oxysporum complex was tested by constructing nuclear and mitochondrial gene genealogies and amplified fragment length polymorphism (AFLP)-based phylogenies for 89 strains representing the known genetic and pathogenic diversity in 8 formae speciales associated with wilt diseases and root and bulb rot. We included strains from clonal lineages of F. oxysporum f. spp. asparagi, dianthi, gladioli, lilii, lini, opuntiarum, spinaciae, and tulipae. Putatively nonpathogenic strains from carnation and lily were included and a reference strain from each of the three main clades identified previously in the F. oxysporum complex; sequences from related species were used as outgroups. DNA sequences from the nuclear translation elongation factor 1alpha and the mitochondrial small subunit (mtSSU) ribosomal RNA genes were combined for phylogenetic analysis. Strains in vegetative compatibility groups (VCGs) shared identical sequences and AFLP profiles, supporting the monophyly of the two single-VCG formae speciales, lilii and tulipae. Identical genotypes were also found for the three VCGs in F. oxysporum f. sp. spinaciae. In contrast, multiple evolutionary origins were apparent for F. oxysporum f. spp. asparagi, dianthi, gladioli, lini, and opuntiarum, although different VCGs within each of these formae speciales often clustered close together or shared identical EF-1alpha and mtSSU rDNA haplotypes. Kishino-Hasegawa analyses of constraints forcing the monophyly of these formae speciales supported the exclusive origin of F. oxysporum f. sp. opuntiarum but not the monophyly of F. oxysporum f. spp. asparagi, dianthi, gladioli, and lini. Most of the putatively nonpathogenic strains from carnation and lily, representing unique VCGs, were unrelated to F. oxysporum f. spp. dianthi and lilii, respectively. Putatively nonpathogenic or rot-inducing strains did not form exclusive groups within the molecular phylogeny. Parsimony analyses of AFLP fingerprint data supported the gene genealogy-based phylogram; however, AFLP-based phylogenies were considerably more homoplasious than the gene genealogies. The predictive value of the forma specialis naming system within the F. oxysporum complex is questioned.

Isolates of Fusarium oxysporum f.sp. gladioli were collected from widely different geographic areas. These isolates were characterized by pathogenicity to two differential gladiolus cultivars, vegetative compatibility, and total genomic DNA restriction fragment length polymorphisms (RFLPs). RFLPs were used to estimate the genetic divergence and relationship among isolates of F. oxysporum. RFLPs were detected by Southern blot hybridization of total genomic DNA with a 3-4 kb DNA probe generated from total DNA of F. oxysporum f.sp. dianthi. Cluster analysis allowed the division of pathogenic strains into three main RFLP groups, each group containing strains with similarity coefficients ranging from 78 to 100%. RFLP groups correlated with vegetative compatibility groups, not with races. Two single pathogenic isolates which could not be assigned to any of the three main vegetative compatibility groups also had distinctive RFLP patterns. Little genetic polymorphism was observed within vegetative compatibility groups, whereas the majority of RFLPs occurred between vegetative compatibility groups, suggesting a common ancestry for strains within a spwcific vegetative compatibility group and a polyphyletic origin for the present special form gladioli. o».. 3... 99 76 no 90 75 101 90 96 99Corm disease PP 0,4,0,0,0 1,2,3,2,3 0,0,0,0,3 0,0,0,0,0 0,0,0,0,2 0,0,0,0.0 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0 rot index N Race 0,0,0,1,1

No abstract

Fusarium oxysporum f.sp. gladioli is a major pathogen of Gladiolus and resistance to this fungus is needed. A standardized screening assay to assess resistance levels in breeding selections must be developed. Corms of cultivars. ranging from susceptible to resistant, were planted either in soil infested with various inoculum levels or incubated in vitro after wound inoculation. The soilgrown corms were rated using relative length of the shoots and average disease rating. In vitro incubated corms were evaluated visually after 6 weeks. All parameters produced similar results. It was concluded that the relative length of shoots of corms after 8 weeks of growing in soil with a high inoculum level combined with the assessment of the average disease rating of the corms after either 8 or 20 weeks is an effective screening assay. Zusammenfassung fusaruim-Resistenz bei Gladiolus: Entwicklung eines Screening-TestsFusarium oxysporum f. sp. gladioli ist ein wichtiges Pathogen von Gladiolus, und zur Eindammung dieser Krankheit ist die Zlichtung resistenter Gladiolen erforderlich. Hierzu muB ein standardisierter Screening-Test entwickelt werden, der die Erfassung verschiedener Resistetizgrade ermoglicht. Knollen anfalliger und resistenter Sorten wurden in Boden gepflanzt, die verschiedene Inokulummengen enthielten, oder nach einer Wundinokuiation in vitro inkubiert. Die Resistenz der im Boden gehaltenen Knollen wurde anhand der relativen Lange der Triebe und des durchschnittlichen AusmaBes der Erkrankung erfaBt. Die in vitro inkubierten Knolien wurden nach sechs Wochen visuel! bonitiert. Aile Parameter fuhrten zu vergleichbaren Ergebnissen. Es wurde gefolgert, daC die Erfassung der relativen Lange der von den Knollen gebildeten Triebe nach achtwochigem Wachstum in einem Boden hohen Inokulumgehalts in Verbindung mit der Bonitur des durchschnitthchen Ausmafles der Erkrankung der Knollen nach acht oder 20 Wochen einen effektiven Screening-Test darstellt.

Fusarium oxysporum f.sp. gladioli (FOG) race 1 infects both large‐ and small‐flowered Gladiolus cultivars. Race 2 isolates infect only small‐flowered cultivars but can be present as epiphytes on large‐flowered plants. When 160 arbitrary 10‐mer oligonucleotide primers were tested on FOG by PCR to find RAPD markers specific for race 1, the RAPD primer G12 amplified two discriminating DNA fragments, AB (609 bp) and EF (1196 bp), in race 1 isolates only. Both fragments were cloned and sequenced. Two pairs of race 1‐specific primers for multiplex PCR were designed. Tests of 112 F. oxysporum isolates by PCR showed that, in almost all cases, race 1 isolates of vegetative compatibility group 0340 could be distinguished with these primers. Seven putative race 1 isolates did not react in multiplex PCR; hybridization studies with labelled AB and EF DNA fragments showed that these isolates belong to separate groups. A bioassay was developed to detect corms that were latently infected with FOG race 1. Gladiolus corms were homogenized and incubated for 5 days at 28°C in a semiselective medium to induce growth of Fusarium. Cultivated mycelium was isolated and subjected to the developed multiplex PCR after standard DNA isolation or disruption by microwave treatment.