Stabilizing Racial Populations of Plant Pathogens by Use of Resistance Genes1
- R. R. Nelson2
Vertical resistance (VR) genes in plants function by restricting the infection site and the infection process of parasites. Such genes are effective against certain races and ineffective against others. Horizontal resistance (HR) genes in plants function by reducing the amount of disease by reducing disease increase. Horizontal resistance is effective to some extent against all races. The use of resistance genes to curb population shifts is examined herein. It is probable that HR curbs population shifts by virtue of its polygenic inheritance which requires that the parasite obtain and accumulate a number of new virulence genes. The use of VR genes in multilines holds some promise, deployment of VR genes probably does not, and pyramiding of VR genes seems most worthy. The concept of stabilizing selection is presented, discussed, evaluated, and deemed of doubtful validity as a means of curbing racial shifts.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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