PLANT RESISTANCE Do Rice Hybrids Have Heterosis for Insect Resistance? A Study with Nilaparvata lugens (Hemiptera: Delphacidae) and Marasmia patnalis (Lepidoptera: Pyralidae)

Antibiosis-based resistance to two insect pests of rice, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae), was compared in 11 F1 hybrids and their parental lines. Our objective was to determine whether hybrids show heterosis (hybrid vigor) for insect resistance or susceptibility. Heterosis is deÞned as the amount by which a hybrid exceeds its midparent value or its better parent. Overall, we did not Þnd evidence of heterosis or heterobeltiosis (a type of heterosis in which a hybrid exceeds its better parent) for antibiosis-based resistance or susceptibility to either of the insects. One hybrid, IR64616H, seemed more resistant toM.patnalis than itsbetterparentbutnoneof theotherhybrids showedheterobeltiosis for resistance or susceptibility to either insect. Three hybrids had resistance toN. lugens that exceeded their midparent value, possibly due to dominant resistance in one of the parents. The increased frequency and severity of insect outbreaks on hybrid rice that have been reported in China may be attributable to factors other than diminished antibiosis in hybrids, such as greater attractiveness of hybrids tomigrating or dispersing insects or differences in agronomic practices applied to hybrids and inbred rice cultivars.