SUMMARY
Cetintas, R., J. A. Brito, and D. W. Dickson. 2008. Virulence of four Florida isolates of Meloidogyne mayaguensis to selected soybean genotypes. Nematropica 38:127-135. The reproduction and virulence of four Florida isolates of Meloidogyne mayaguensis to the root-knot nematode resistant ('Benning', 'Boggs', 'Bragg', 'Forrest', 'Haskell', 'Lee 74'and G-93-9009) and susceptible ('Bossier', 'GoSoy 17', 'Pickett') soybean genotypes were evaluated in a growth chamber. Two levels of each nematode isolate (low = 2,500 eggs or J2/ plant; high = 5,000 eggs or J2/ plant) were used. None of the genotypes were immune to the isolates of M. mayaguensis. Differences in reproduction and virulence were detected among the nematode isolates at both inoculum levels. All four isolates overcame the root-knot nematode resistance genes, including the Mir1 gene. The root-knot nematode resistant soybean 'Bragg' was resistant (egg mass index values (EMI) ranging from 0.1-2.0) to isolates 2 and 3, but susceptible (EMI > 2) to isolate 1 at both inoculum levels, whereas 'Forest', which possess the Mir1 gene was resistant to only isolate 3. The root-knot nematode resistant soybean 'Boggs' and line G93-9009 were resistant to isolate 4. All soybean genotypes were susceptible to isolate 1 at both inoculum levels, except that soybean 'Lee 74' sustained low egg mass (EMI = 2.00) at the low inoculum level (P = 0.05). The results of this study showed for the first time that gene(s) that confer resistance to at least one of the major root-knot nematode species in soybean may also confer resistance to some isolates of M. mayaguensis.