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

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The central vacuole is the main site of accumulation of many water-soluble secondary metabolites such as anthocyanins and other phenolic compounds. It is generally accepted that the biosynthesis of anthocyanins and other flavonoid glycosides occurs in the cytosol and that these compounds are then transported to the central vacuole across the tonoplast (Hrazdina and Wagner, 1985; Hrazdina et al., 1987). The mechanisms for transport to the vacuoles have not been clearly established. However, it was reported recently that anthocyanin is conjugated with glutathione in a reaction that is catalyzed by glutathione S-transferase (encoded in maize by the Bronze-2 gene) and that this conjugate is then transported to the vacuoles by the glutathione pump in the tonoplast (Marrs et al., 1995; Marrs, 1996). Martinoia et al. (1993) showed that the uptake of glutathione S-conjugates of N-ethylmaleimide and of metolachlor into the vacuoles was mediated by a specific ATPase

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.