EXPERIMENTAL SELECTION OF A BROWN PLANTHOPPER POPULATION ON MIXTURES OF RESISTANT RICE LINES

The adaptation of the brown planthopper (BPH) to mixture of resistant rice lines was studied. The BPH population which had no ability to inf est any resistant rice varieties in Japan was reared on the three plot s of single resistant lines and the four mixtures of two to three resi stant lines. BPH adapted to the single resistant lines by the fifth ge neration of selection and to the mixtures by the ninth generation. The BPH colonies selected on the mixtures were more virulent than those o n the single resistant lines, which enabled to infest all the componen t lines. These results revealed that the mixtures of two to three BPH resistant lines were only effective to delay the development of the va rietal resistance-breaking populations for some geneartions but ineffe ctive to prevent it.