Reaction of a diallel cross of maize to Meloidogyne incognita under field conditions

Abstract

Meloidogyne incognita (Kofoid and White) Chitwood is an important pathogen of maize ( Zea mays L.), cotton ( Gossypium hirsutum L.) and soybean ( Glycine max (L.) Merr.) in the southeastern USA. Maize has been used, but not always successfully, in rotation with the other two crops to reduce nematode populations. The use of hybrids that support only low rates of M. Incognita reproduction should not only limit damage to the maize crop, but also to the other crops. Unfortunately, maize hybrids with resistance to M. incognita are not commercially available. A diallel cross of inbred lines with varying levels of resistance to M. incognita reproduction was previously evaluated in the greenhouse. The current investigation was undertaken to evaluate F 1 hybrids of the diallel cross for nematode reproduction in field naturally infested with M. incognita in 1989 and 1990. Egg counts were analyzed using Griffing's Method 4, Model I. General combining ability was a significant source of variation in egg production, but specific combining ability was not. Estimates of general combining-ability effects for Mp307 were significantly and negative, indicating that hybrids with this inbred line as a parent tended to be most resistant. The results of the field evaluations were consistent with the earlier evaluation of M. incognita reproduction on these F 1 hybrids. The results further suggest that maize hybrids with resistance to M. incognita reproduction can be developed.