The green rice leafhopper (GRH), Nephotettix cincticeps Uhler, is a serious insect pest of cultivated rice (Oryza saliva L.) in temperate East Asia. Six GRH-resistance genes (Grh1, Grh2, Grh3, Grh4, Grh5, and Grh6) and one quantitative trait locus (QTL; qGRH4) have been identified. We selected near-isogenic lines (NILs) carrying Grh1, Grh2, Grh4, Grh5, Grh6, and qGRH4 with the japonica genetic background (Taichung 65 cultivar) by means of marker-assisted selection using new simple sequence repeat markers flanking the GRH-resistance genes and QTL. We also developed three pyramided lines (PYLs; Grh2/Grh6-PYL, Grh4/Grh6-PYL, and Grh5/qGRH4-PYL) using each NIL that carried a GRH-resistance gene or QTL. The NILs, PYLs, and donor parents were evaluated by using an antibiosis test. The resistance of Grh1-NIL and Grh5-NIL did not differ significantly from those of the donor parents, whereas the resistances of Grh2-NIL and Grh6-NIL were significantly lower than those of the donor parents. Grh4-NIL and qGRH4-NIL were highly susceptible. The resistance levels of the pyramided lines for Grh2 and Grh6, Grh4 and Grh6, and Grh5 and qGRH4 demonstrated a gene pyramiding effect that significantly increased their resistance. The developed NILs and PYLs should be useful genetic resources for rice improvement and deployment of the resistance genes.
