considered agnostic to nematodes. However, raising soil populations to desired levels often

 resulted in phytotoxic symptoms in plants. Large amounts of nitrogen were required for

 effective use of this treatment, and it proved to be cost prohibitive.

 Kloepper et al. (1992) looked at the use of rhizobacteria to treat seeds. This study found

 that rhizobacteria derived from the roots of antagonistic plants may be beneficial in reducing

 populations of phytopathogenic nematodes. The use of soil amendments will require further

 research before commercial application of this method could be considered.


 Host Plant Resistance

 Host plant resistance (HPR) is an alternative that enables the plant to grow and produce,

 despite populations of pests. This method identifies genes that confer resistance to a given plant,

 and once identified, is introduced into the desired plant. For example, the gene Mi was

 identified for resistance to root knot nematode in the wild species of tomato. This gene was then

 introduced into varieties of desirable cultivars of tomato (Fassuliotis, 1987). However, the

 identified Mi gene is considered heat instable, therefore, in regions of warm temperatures the

 resistance to root knot nematode is lost (Roberts, 1992). Genes for resistance have also been

 identified for other crops such as sugar beet and beans (Fassuliotis, 1987). Once the gene has

 been identified and introduced into the desired cultivar, however, another problem has been that

 new virulent races or pathotypes occur, which can overcome the new resistant cultivar

 (Fassuliotis, 1987). As these experiments suggest, host plant resistance for use in commercial

 operations is limited due to problems associated with identification and transfer of genes to

desired cultivars (Roberts, 1992).