Fusarium oxysporum is an ascomycetous fungus that is well-known as a soilborne plant pathogen. In addition, a large population of nonpathogenic F. oxysporum (NPF) inhabits various environmental niches, including the phytosphere. To obtain an insight into the origin of plant pathogenic F. oxysporum, we focused on the tomato (Solanum lycopersicum) and its pathogenic F. oxysporum f. sp. lycopersici (FOL). We collected F. oxysporum from wild and transition Solanum spp. and modern cultivars of tomato in Chile, Ecuador, Peru, Mexico, Afghanistan, Italy, and Japan, evaluated the fungal isolates for pathogenicity, VCG, mating type, and distribution of SIX genes related to the pathogenicity of FOL, and constructed phylogenies based on ribosomal DNA intergenic spacer sequences. All F. oxysporum isolates sampled were genetically more diverse than FOL. They were not pathogenic to the tomato and did not carry SIX genes. Certain NPF isolates including those from wild Solanum spp. in Peru were grouped in FOL clades, whereas most of the NPF isolates were not. Our results suggested that the population of NPF isolates in FOL clades gave rise to FOL by gaining pathogenicity.

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This study developed a loop-mediated isothermal amplification (LAMP) assay for detection and differentiation of Fusarium oxysporum f. sp. lycopersici (Fol) race 1 by using three primer sets targeting for the SIX4 and SIX5 genes. These genes are present together only in Fol race 1. This method can detect Fol race 1 in infected tomato stems without DNA extraction, affording an efficient diagnosis of Fusarium wilt on tomatoes in the field.

Asian soybean rust caused by the fungal pathogen Phakopsora pachyrhizi is the most devastating disease of soybean. The host cultivar specificity of the pathogen shows considerable differentiation depending on the area and season of its emergence. Although resistance genes for P. pachyrhizi (Rpp) have been reported in several soybean varieties, the genetic background of these varieties is highly differentiated. Furthermore, some of the varieties harbor unknown genetic factors in addition to Rpp that could influence resistance reactions against the pathogen. In order to gain a comprehensive understanding of Rpp-P. pachyrhizi interactions, homogenous plant material harboring Rpp genes is necessary. in this study, we bred Rpp-near isogenic lines (Rpp-niLs), which retained identical plant characters originating from a single genetic background, and accordingly showed lowvariant compatible/incompatible reactions against the pathogen. these Rpp-niLs can be used as genetic resources for studying P. pachyrhizi epidemiology and elucidating resistance mechanisms. compatible/incompatible relationships between the soybean rust resistance gene Rpp and isolates of the pathogen P. pachyrhizi are clearly distinguishable using the Rpp-niLs bred in this study. Asian soybean rust (ASR) is the most devastating disease of soybean production worldwide. The disease is caused by the obligate biotrophic fungal pathogen Phakopsora pachyrhizi Sydow and Sydow 1,2. Currently, the main strategy for control the disease is the use of fungicides 3. Recently, however, pathogen resistance to fungicides has frequently been reported 1,4. Genes conferring resistance against P. pachyrhizi (Rpps) have also been used to protect soybean from the disease, with eight Rpp loci being reported from soybean and introduced into soybean varieties to date 5-11. For some of these Rpps, several alleles have reported 11 ; for example, Rpp2 has been detected in PI 230970 12,13 and Iyodaizu B 14 , and Rpp3 has been reported from FT2 (PI 628932) 15 , PI 462312 12,16 , and Hyuuga 17,18. Breeding for ASR-resistant soybean by introducing Rpps is also emerging as a major strategy for disease control. Pyramiding of two or more Rpps into a single variety has produced plants showing strong resistance against the pathogen 19,20 , and in this regard, several soybean varieties have been used as a source of Rpps. These varieties are also used for inoculation tests to distinguish the host specificity of P. pachyrhizi isolates 21,22. A set of ASR-resistant varieties are determined as "Rpp differentials" that possess a single Rpp gene. However, in some cases, differential varieties exhibit unclear susceptible/resistant reaction against the pathogens, which indicates that the genetic background of some of the differential varieties influences the susceptible/resistant phenotype 19,23. Furthermore, plant characters such as growth rate and size of leaves differ among Rpp differentials, given that these varieties originate from different countries (Japan, China, India, Indonesia, and Bra...

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