The tomato cultivar Nemared is resistant to the root-knot nematodes Meloidogyne incoxnita (Kofoid and White, 1919) Chitwood, 1949 and M. javanica (Treub, 1885) Chitwood, 1949, as reported by Malo (1964). However, a seed lot of this cultivar received at the IVT in 1970 was found to be susceptible. Medina Filho and Stevens (1980) also reported susceptibility of their seed lot of 'Nemared.' In earlier tests at the IVT, a seed lot of Nemared received in 1964, appeared to be resistant. Both seed lots were received from the Oklahoma Seed Stocks Foundation.
Two seed lots at the IVT were tested for resistance to M. incoitnita in order to investigate if the contradicting observations are due to differences between the seed lots. The method used has been summarized by Boukema et al. (1984). The test was carried out in a climate chamber at 24 deg. C and 70% RH. Cvs Nematex and Moneymaker were used as resistant and susceptible standards, respectively. From the test results (Table 1) it can be concluded that the contradicting observations, obtained earlier with cv. Nemared, are due to the fact that the seed lot received in 1970 (IVT nr. 701415) differs from the original cv. Nemared at least in its susceptibility to root-knot nematodes. This is possibly also the case with seed lots received by others in the same period.
Table 1. Mean number of galls/plant 4 weeks after inoculation with 50 larvae/ plant of M. incognita (6 replications of 4 plants).
______________________________________________ Tomato cv IVT seed lot nr. Nr. galls/plant ______________________________________________ Nematex 82600 0.0 Moneymaker 83314 8.1 Nemared 701415 6.9 Nemared G598* 0.1 ______________________________________________*G598 is a multiplication of seed lot nr. 64060 received in 1964.
Literature cited:
Boukema, I.W., K. Hofman, H. Toxopeus and F.M.W. Lamers. 1984. An efficient screening method for root-knot nematode resistance in cucurbits and crucifers. In: W. Lange, A.C. Zeven and N.G. Hogenboom (eds.). Efficiency in Plant Breeding, Proceedings of the 10th Congress of Eucarpia, Pudoc, Wageningen, p. 299.
Malo, S.E. 1964. A review of plant breeding for nematode resistance. Proc. Soil and Crop Sci. Soc. of Florida. 24:354-365.
Medina Filho, H.P. and M.A. Stevens. 1980. Tomato breeding for nematode resistance: survey of resistant varieties for horticultural characteristics and genotype of acid phosphatases. Acta Horticulturae 100:383-393.