A study was made of the genetics of resistance to the soybean …

• Abstract
• Introduction
• Materials and Methods
• Results and Discussion
• References
• Table 1

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe, 1952) is considered to be the most important problem for soybeans (Noel, 1992). Losses can reach 100%, depending on the pathogen density in the soil. In Brazil there is not much information about the damage caused by the SCN since it was first detected in 1992, in the counties of Nova Ponte, Iraí de Minas and Romaria, Minas Gerais State. Four years later, SCN was found in 62 counties distributed in seven states, race 3 being predominant (EMBRAPA, 1996).

The use of resistant cultivars in rotation with susceptible ones and non-host species is the most economic and reliable method for controlling SCN (Wrather et al., 1984). The resistance mechanism is hypersensitivity, which determines the death of infected cells and blocks the nematode cycle (Schmidt and Noel, 1984). The genetics of soybean resistance to SCN, race 3, is complex and studies carried out by several authors (Caldwell, 1960; Rao-Arelli and Anand, 1988; Rao-Arelli et al., 1992), with North-American soybean genotypes, found that two or three recessive and one dominant gene were involved in resistance.

To develop soybean cultivar resistant to SCN it is necessary the knowledge of number of genes related to resistance, as well as the type of gene action and the heritability of this character. This knowledge will allow the breeder to use more efficient selection procedures and a better use of the variability in the segregating population.