Evaluation of host suitability for meloidogyne species of rotational crops used in tobacco cultivation in South Africa
Crop rotation is the single most useful practice that can realistically be applied to annual and short- term perennial crops. It is also not uncommon for a single field to have several nematode species present that could have a limiting effect on a specific crop. The root-knot nematodes Meloidogyne incognita races 2 and 4 and M. javanica are the key nematode problems in South Africa. Depending on the time and population density, root-knot nematodes can cause considerable damage to a tobacco crop. Crop-rotation schemes are complicated by the presence of different root-knot nematode species and races because the reproduction of different species and of Meloidogyne varies with crop and cultivar. It is therefore necessary to know the host-status of the cultivars of crops to the major root-knot nematode species. A project was initiated to evaluate the resistance of the various cultivars of the rotational crops to the principal root-knot nematode species and races. Until 1999 extensive greenhouse screenings have been conducted by ARC-IIC. Evaluations were done on a cultivar level in the greenhouse and information on 310 entries, including cash crops, pasture grasses, cover crops and lesser known crops with a specific niche market, is available. The project was resumed in 2007 and to date cultivars of various crops such as millet, sunn hemp, oats, maize, wheat, pea and rye grass cultivars were evaluated. From these crops the rye grass cultivar Caversham, oat cultivars Witteberg and Kompasberg and wheat cultivars Olifants, Baviaans, Kariega and Steenbras, were resistant to the 3 major root-knot nematodes in South Africa, whilst the pea cultivars Raxel and Bolero were susceptible and the other cultivars of crops evaluated, varied between susceptible, tolerant and resistant.