The Root-Knot Nematode Meloidogyne fallax on Strawberry in the Netherlands

Abstract

The root-knot nematode Meloidogyne fallax Karssen is closely related to M. chitwoodi Golden, O'Bannon, Santo & Finley. Both species have a wide host range and have been designated as quarantine nematodes by several countries. Strawberry (Fragaria ananassa L.) is considered a poor host for M. chitwoodi (2,3), but the host status for M. fallax in unknown. During 2003, a host suitability study was performed with four common strawberry cultivars (Ciflorette, Elsanta, Kimberly, and Mara des bois) on a field naturally infested with M. fallax near Wintelre, the Netherlands. The identity of the nematode was confirmed, prior to and after the test, by using morphological characteristics, isozymes, and polymerase chain reaction (PCR). The field was not infested with M. hapla Chitwood. The host test included 15 replicates per cultivar and started in April with a mean initial M. fallax density of approximately 4,500 second-stage juveniles per 100 ml of soil. The plants used in the field trial were multiplied by cuttings and grown on artificial substrate free from any Meloidogyne species. Upon plant harvesting in October, the number of root galls were counted and cvs. Mara des bois and Ciflorette did not show any typical root-knot symptoms, while cvs. Elsanta and Kimberly expressed only a few small galls. Additionally, high numbers of nematodes were found in the roots using the centrifugal floating method (1). The mean numbers of isolated nematodes for all cultivars (females, 116; males, 80; second-stage juveniles, 6,636; third- and fourth-stage juveniles, 49; and eggs, 920 per 10 g of roots) suggests that the tested strawberry cultivars are good hosts for M. fallax despite the lack of clear root galling or visible plant grow reduction as has been observed in the past for M. javanica on strawberry (4). To our knowledge, this is the first report of strawberry as a host for M. fallax, and it suggests that M. fallax could be spread by strawberry transplant grown in M. fallax infested soil. The Dutch Plant Protection Service is currently discussing appropriate action, such as an additional root-knot nematode test in addition to visual root inspection, before strawberry plants are shipped and cultivated. References: (1) W. A. Coolen and J. D'Herde. A method for the quantitative extraction of nematodes from plant tissue. Ghent State Agriculture Research Centre, 1972. (2) A. M. Golden et al. J. Nematol. 12:319, 1980. (3) J. H. O'Bannon et al. Plant Dis. 66:1045, 1982. (4) D. P. Taylor and C. Netscher. Cah. O.R.S.T.O.M, Ser. Biol. 10:247, 1975.