The Colletotrichum acutatum species complex

Manual of microbiological methods

A two-locus DNA sequence database for typing plant and human pathogens within the Fusarium oxysporum species complex

The grapevine (Vitis spp.) undoubtedly represents one of the woody crops most widely grown in temperate climates, and a highly valuable agricultural commodity. As most of the vegetatively propagated crops, grapevines are exposed to the attacks of a variety of pests and pathogens among which infectious intracellular agents (viruses, viroids, phloem‑ and xylem‑limited prokaryotes) play a major role, causing heavy losses, shortening the productive life of vineyars, and endangering the survival itself of affected vines. The importance of the grapevine industry and the magnitude of the problems caused by these pathogens has generated wide interest which, in turn, has fostered intensive research which has been especially active at the international scale from the late 1950’s onwards.

Directory of virus and virus-like diseases of the grapevine and their agents

This review is intended to provide plant pathologists and other scientists with a current overview of the most important Fusarium phytopathogens and mycotoxin producers. Knowledge of Fusarium species diversity and their evolutionary relationships has increased dramatically due to the application of multilocus molecular phylogenetics and genealogical concordance phylogenetic species recognition over the past 15 years. Currently Fusarium is estimated to comprise at least 300 genealogically exclusive phylogenetic species; however, fewer than half have been formally described. The most important plant pathogens reside in the following four groups: the F. fujikuroi species complex noted for Bakanae of rice, ear rot of maize, pitch canker of pine and several species that contaminate corn and other cereals with fumonisin mycotoxins; the F. graminearum species complex including the primary agents causing Fusarium head blight of wheat and barley that contaminate grain with trichothecene mycotoxins; the F. oxysporum species complex including vascular wilt agents of over 100 agronomically important crops; and the F. solani species complex, which includes many economically destructive foot and root rot pathogens of diverse hosts. Several other Fusarium phytopathogens reported from Japan and nested within other species complexes are reviewed briefly. With the abandonment of dual nomenclature, a broad consensus within the global community of Fusarium researchers has strongly supported the unitary use of the name Fusarium instead of several teleomorph names linked to it. Plant pathologists and other scientists needing accurate identifications of Fusarium isolates are encouraged to use Fusarium-ID and Fusarium MLST, Internet accessible websites dedicated to the molecular identification of Fusarium species.

Systematics of key phytopathogenic Fusarium species: current status and future challenges

Pathogenic variation among 26 Japanese isolates of Fusarium oxysporum f. sp. lactucae (FOL) was tested using 21 lettuce cultivars to select commercial lettuce cultivars as race differential indicators. Cultivar Costa Rica No. 4 was resistant to race 1 but susceptible to race 2, consistent with the conventional standard differential line VP1010. Cultivar Banchu Red Fire was susceptible to race 1 but resistant to race 2, which showed an opposite type of reaction as another differential line VP1013. Cultivar Patriot was susceptible to both races. The resistance reactions of the three cultivars under field conditions were identical with that observed in the seedlings. Thus cv. Costa Rica No. 4 and cv. Banchu Red Fire can be used as differential hosts to identify pathogenic races of FOL. This differential system showed that all FOL isolates obtained from diseased butterhead lettuce in Fukuoka, Japan were new races (i.e., pathogenic to three cultivars). We propose that the new race be designated race 3. Isolates of FOL, the pathogen of Fusarium wilt in lettuce, obtained from California showed the same reaction as that of race 1. Furthermore, the Japanese isolate SB1-1 (race 1) and California isolate HL-2 belonged to the same vegetative compatibility group. Our results suggest that both of the fungi are the same forma specialis.

Race 3, a new race of Fusarium oxysporum f. sp. lactucae determined by a differential system with commercial cultivars

In 1995, Fusarium root rot of crisp head lettuce, caused by Fusarium oxysporum f. sp. lactucae, was simultaneously found in the Shiojiri and Kawakami areas of Nagano Prefecture, Japan. The Shiojiri and Kawakami isolates differed in pathogenicity to lettuce cultivars. Because of this distinct physiological specialization, these Shiojiri and Kawakami isolates should be designated as race 1 and race 2, respectively, using lines VP1010 (highly resistant to race 1), VP1013 (highly resistant to race 2) and variety Patriot (highly susceptible to both races) as differential varieties. This is the first report of races of Fusarium oxysporum f. sp. lactucae,

Physiological specialization of fusarium oxysporum f. sp. lactucae, a causal organism of Fusarium root rot of crisp head lettuce in Japan

The genetic relationship between the vegetative compatibility groups (VCGs) and between physiological races of Fusarium oxysporum f. sp. lactucae (FOL), the causal pathogen of lettuce root rot, was determined by analyzing the intergenic spacer (IGS) region of its ribosomal DNA. A total of 29 isolates containing a type strain were tested: 24 Japanese isolates, 2 Californian isolates, and 3 Italian isolates. Three races (races 1, 2, and 3) were found in Japan, and race 1 was also distributed in California and Italy. Races 1, 2, and 3 each belonged to a distinct VCG: VCG-1, VCG-2, and VCG-3 (VCG-3-1, VCG-3-3), respectively. Phylogenetic (neighbor-joining) analysis of the IGS sequences revealed that races 1, 2, and 3 coincided with three phylogenetic groups (PG): PG-1, PG-2, and PG-3, respectively. These results indicate that the three races are genetically quite different and have a strong correlation with VCGs and phylogenetic groupings.

Phylogenetic relationships between the lettuce root rot pathogen Fusarium oxysporum f. sp. lactucae races 1,2, and 3 based on the sequence of the intergenic spacer region of its ribosomal DNA

Six4, a small protein secreted by Fusarium oxysporum f. sp. lycopersici (Fol) in tomato xylem sap during infection, triggers Fol race 1-specific resistance (I) in tomato. SIX4 is regarded as an avirulence gene. Although SIX4 is considered unique to Fol race 1, we detected this gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans (Foc) by PCR. Because the genes from Foc and SIX4 in Fol were >99 % identical at the nucleotide level, the Foc gene was designated FocSIX4. The expression of FocSIX4 was detected by RT-PCR in stems and roots of cabbage 8 days after infection with Foc. In contrast with Fol, disruption of FocSIX4 in Foc did not increase virulence to Foc-resistant cabbage cvs. Shutoku-SP and Koikaze. On the contrary, the disruptants had reduced virulence not only on Foc-resistant cultivars but also on Foc-susceptible cv. Shikidori. These results suggested that FocSIX4 is involved in virulence, but not in avirulence, in the cabbage yellows fungus.

An avirulence gene homologue in the tomato wilt fungus Fusarium oxysporum f. sp. lycopersici race 1 functions as a virulence gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans

One hundred and sixteen isolates of Fusarium oxysporum f. sp. lactucae obtained from 85 fields in three crisphead lettuce-producing areas in Nagano Prefecture, Japan were typed for races using differential cultivars Patriot, Banchu Red Fire and Costa Rica No. 4. They were also grouped into vegetative compatibility groups (VCGs) using complementation tests with nitrate non-utilizing (nit) mutants. Two California strains reported as F. oxysporum f. sp. lactucum, a type culture of F. oxysporum f. sp. lactucae, and 28 avirulent isolates of F. oxysporum obtained from crisphead lettuce were included for comparison. Among Nagano isolates, 66 isolates were identified as race 1, and 50 as race 2. Race 1 strains derived from Shiojiri and Komoro cities and race 2 from Kawakami village and Komoro city. All isolates of race 2 were biotin auxotrophs, and the race could be distinguished based on its requirement for biotin on minimal nitrate agar medium (MM). Pathogenic isolates were classified into two VCGs and three heterokaryon self-incompatible isolates. Strong correlations were found between race and VCG. All the race 1 strains were assigned to VCG 1 except self-incompatible isolates, and all the race 2 strains to VCG 2. The 28 avirulent isolates of F. oxysporum were incompatible with VCG 1 and VCG 2. California strains was vegetatively compatible with VCG 1, and they were assigned to race 1. Based on vegetative compatibility, these two races of F. oxysporum f. sp. lactucae may be genetically distinct, and F. oxysporum f. sp. lactucae race 1 is identical to F. oxysporum f. sp. lactucum.

Hideki Ogiso

Papers

Race 3, a new race of Fusarium oxysporum f. sp. lactucae determined by a differential system with commercial cultivars

Physiological specialization of fusarium oxysporum f. sp. lactucae, a causal organism of Fusarium root rot of crisp head lettuce in Japan

Phylogenetic relationships between the lettuce root rot pathogen Fusarium oxysporum f. sp. lactucae races 1,2, and 3 based on the sequence of the intergenic spacer region of its ribosomal DNA

An avirulence gene homologue in the tomato wilt fungus Fusarium oxysporum f. sp. lycopersici race 1 functions as a virulence gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans

Physiological Races and Vegetative Compatibility Groups of Fusarium oxysporum f. sp. lactucae Isolated from Crisphead Lettuce in Japan