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 Mi-virulent 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.
Ionit
I
Iberkleid
Rachel
R
Ozalvo
Lidia
L
Feldman
Moshe
M
Elbaz
Bucki
B
Patricia
Sigal Brown
SB
Horowitz
D000818:Animals; D003517:Cyclopentanes / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D060467:Disease Resistance; D005838:Genotype; D006790:Host-Parasite Interactions; D007557:Israel; D018551:Solanum lycopersicum / Q000166:cytology / Q000235:genetics / Q000469:parasitology / Q000502:physiology*; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics*; D012098:Reproduction; D012459:Salicylates / Q000378:metabolism; D015398:Signal Transduction; D014431:Tylenchoidea / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D014774:Virulence
D003517:Cyclopentanes; D017931:DNA Primers; C117349:MI-1 protein, Lycopersicon esculentum; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012459:Salicylates; C011006:jasmonic acid