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Phytopathology
Iberkleid, I., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel, Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
Ozalvo, R., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Feldman, L., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Elbaz, M., Negev Research and Development Station, Habsor Farm, Israel
Patricia, B., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Horowitz, S.B., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
The behavior of naturally virulent Meloidogyne isolates toward the tomato resistance gene Mi in major tomato-growing areas in Israel was studied for the first time. Virulence of seven selected isolates was confirmed over three successive generations on resistant (Mi-carrying) and susceptible (non-Mi-carrying) tomato cultivars. Diagnostic markers verified the predominance of Meloidogyne javanica among virulent isolates selected on resistant tomato cultivars or rootstocks. To better understand the determinants of nematode selection on Mi-carrying plants, reproduction of Mi-avirulent and virulent isolates Mjav1 and Mjv2, respectively, measured as eggs per gram of root, on non-Mi-carrying, heterozygous (Mi/mi) and homozygous (Mi/Mi) genotypes was evaluated. Although no reproduction of Mjav1 was observed on Mi/Mi genotypes, some reproduction was consistently observed on Mi/mi plants; reproduction of Mjv2 on the homozygous and heterozygous genotypes was similar to that on susceptible cultivars, suggesting a limited quantitative effect of the Mi gene. Histological examination of giant cells induced by Mivirulent versus avirulent isolates confirmed the high virulence of Mjv2 on Mi/mi and Mi/Mi genotypes, allowing the formation of well-developed giant-cell systems despite the Mi gene. Analysis of the plant defense response in tomato Mi/Mi, Mi/mi, and mi/mi genotypes to both avirulent and virulent isolates was investigated by quantitative real-time polymerase chain reaction. Although the jasmonate (JA)-signaling pathway was clearly upregulated by avirulent and virulent isolates on the susceptible (not carrying Mi) and heterozygous (Mi/mi) plants, no change in signaling was observed in the homozygous (Mi/Mi) resistant line following incompatible interaction with the avirulent isolate. Thus, similar to infection promoted by the avirulent isolate on the susceptible genotype, the Mi-virulent isolate induced the JA-dependent pathway, which might promote tomato susceptibility during the compatible interaction with the homozygous (Mi/Mi) resistant line. These results have important consequences for the management of Mi resistance genes for ensuring sustainable tomato farming. © 2014 The American Phytopathological Society.
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Responses of tomato genotypes to avirulent and Mi-virulent Meloidogyne javanica isolates occurring in Israel
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Iberkleid, I., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel, Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
Ozalvo, R., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Feldman, L., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Elbaz, M., Negev Research and Development Station, Habsor Farm, Israel
Patricia, B., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Horowitz, S.B., Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, Israel
Responses of tomato genotypes to avirulent and Mi-virulent Meloidogyne javanica isolates occurring in Israel
The behavior of naturally virulent Meloidogyne isolates toward the tomato resistance gene Mi in major tomato-growing areas in Israel was studied for the first time. Virulence of seven selected isolates was confirmed over three successive generations on resistant (Mi-carrying) and susceptible (non-Mi-carrying) tomato cultivars. Diagnostic markers verified the predominance of Meloidogyne javanica among virulent isolates selected on resistant tomato cultivars or rootstocks. To better understand the determinants of nematode selection on Mi-carrying plants, reproduction of Mi-avirulent and virulent isolates Mjav1 and Mjv2, respectively, measured as eggs per gram of root, on non-Mi-carrying, heterozygous (Mi/mi) and homozygous (Mi/Mi) genotypes was evaluated. Although no reproduction of Mjav1 was observed on Mi/Mi genotypes, some reproduction was consistently observed on Mi/mi plants; reproduction of Mjv2 on the homozygous and heterozygous genotypes was similar to that on susceptible cultivars, suggesting a limited quantitative effect of the Mi gene. Histological examination of giant cells induced by Mivirulent versus avirulent isolates confirmed the high virulence of Mjv2 on Mi/mi and Mi/Mi genotypes, allowing the formation of well-developed giant-cell systems despite the Mi gene. Analysis of the plant defense response in tomato Mi/Mi, Mi/mi, and mi/mi genotypes to both avirulent and virulent isolates was investigated by quantitative real-time polymerase chain reaction. Although the jasmonate (JA)-signaling pathway was clearly upregulated by avirulent and virulent isolates on the susceptible (not carrying Mi) and heterozygous (Mi/mi) plants, no change in signaling was observed in the homozygous (Mi/Mi) resistant line following incompatible interaction with the avirulent isolate. Thus, similar to infection promoted by the avirulent isolate on the susceptible genotype, the Mi-virulent isolate induced the JA-dependent pathway, which might promote tomato susceptibility during the compatible interaction with the homozygous (Mi/Mi) resistant line. These results have important consequences for the management of Mi resistance genes for ensuring sustainable tomato farming. © 2014 The American Phytopathological Society.
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