Development of near-isogenic lines and pyramided lines carrying resistance genes to green rice leafhopper (Nephotettix cincticeps Uhler) with the Taichung 65 genetic background in rice (Oryza sativa L.)

Abstract

Development of near-isogenic lines and pyramided lines carrying resistance genes to green rice leafhopper (Nephotettix cincticepsUhlerThe green rice leafhopper (GRH), Nephotettix cincticeps Uhler, is a serious insect pest of cultivated rice (Oryza sativa 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.

The rice <i>GRH2</i> and <i>GRH4</i> activate various defense responses to the green rice leafhopper and confer strong insect resistance

“…The GRH resistance test was performed as described previously (Fujita et al 2010). Briefly, seedlings at the second-leaf stage were infested with 7 to 10 first-or second-instar nymphs in test tubes.…”

“…An indica cultivar, DV85, carrying GRH2 and GRH4 shows resistance to GRH (Fujita et al 2010). GRH2-NIL (TGRH11), GRH4-NIL (TGRH16) and GRH2/GRH4-PYL (TGRH29) were developed by introducing GRH2 and GRH4 from DV85 (Fujita et al 2006(Fujita et al , 2010.…”

“…TGRH29 has substituted segments including GRH2 and GRH4. TGRH11 exhibits enhanced resistance to GRH insects: the nymph mortality on GRH2-NIL is about 75% at 3 days after infestation (Fujita et al 2010). GRH2/GRH4-PYL showed higher nymph mortality than GRH2-NIL (Fujita et al 2006).…”

“…Genetic analyses using molecular markers have identified 6 loci and a quantitative trait locus (QTL) with a minor effect on GRH resistance (Fujita et al 2010). However, none of these GRH resistance genes has been cloned to date.…”

“…GRH2 and GRH4 are found on chromosomes 11 and 3 of Lepe dumai and DV85, respectively (Fukuta et al 1998;Kadowaki et al 2003). Two near-isogenic lines (NILs) and a pyramided line (PYL) were developed by introducing GRH2 and GRH4 (Fujita et al 2006(Fujita et al , 2010. TGRH11 has a substituted segment including GRH2 on chromosome 11 from DV85.…”