Elevated temperatures diminish the effects of a highly resistant rice variety on the brown planthopper

Abstract

This study compares the effects of temperature (constant at 15, 20, 25, 30 and 35 °C) on adult longevity, oviposition, and nymph development of the brown planthopper, Nilaparvata lugens, on susceptible and resistant rice varieties. The resistant variety contained the BPH32 gene. In our experiments, nymphs failed to develop to adults at 15, 20 and 35 °C on either variety. Host resistance had its greatest effect in reducing adult survival at 20–25 °C and its greatest effect in reducing nymph weight gain at 25 °C. This corresponded with optimal temperatures for adult survival (20–25 °C) and nymph development (25–30 °C). At 25 and 30 °C, adult females achieved up to three oviposition cycles on the susceptible variety, but only one cycle on the resistant variety. Maximum egg-laying occurred at 30 °C due to larger numbers of egg batches produced during the first oviposition cycle on both the susceptible and resistant varieties, and larger batches during the second and third oviposition cycles on the susceptible variety; however, resistance had its greatest effect in reducing fecundity at 25 °C. This revealed a mismatch between the optimal temperatures for resistance and for egg production in immigrating females. Increasing global temperatures could reduce the effectiveness of anti-herbivore resistance in rice and other crops where such mismatches occur.

Interactions between Rice Resistance to Planthoppers and Honeydew-Related Egg Parasitism under Varying Levels of Nitrogenous Fertilizer

“…Our experiments were conducted on relatively young plants because maximum egg laying by BPH and WBPH occurs in young plants [ 59 ] and egg parasitoids are most abundant at early crop stages [ 38 , 60 ]. We found no significant effect of variety on egg laying by either planthopper species, or by GLH ( Table S1 ); however, recent studies have shown that egg laying by BPH under no-choice conditions is heavily affected by the host of the female parent (i.e., TN1 in this study), with reductions in egg laying apparent as a lack of successive oviposition cycles [ 61 ]. The success of IR62 therefore relies on effective suppression, or losses in the reproductive potential of early generations of nymphs produced by immigrating females, which occurs during early crop stages.…”

The Impact of Climate Change on the Resistance of Rice Near-Isogenic Lines with Resistance Genes Against Brown Planthopper

“…b IR24 and NIL-BPH20. Means in each column followed by a different letter differ significantly (P < 0.05) high temperature (34-35°C, the prediction temperature of 2100) would greatly reduce N. lugens survival rate (Horgan et al 2020;Horgan et al 2021a;Horgan et al 2021b;Wang et al 2010).…”

“…However, in our study, several BPH resistance genes (BPH4, BPH9, BPH10, BPH18, BPH21, BPH21, BPH32, and BPH2 + 32) would lose their resistance due to climate change. In addition, another three BPH resistant varieties, IR26 (BPH1), IR36 (BPH2) and IR62 (BPH26 + 32), would lose the resistance under elevated temperature (Horgan et al 2021a;Wang et al 2010). These results imply that we need to use these insect-resistance traits/genes very carefully to prevent the development of a loss-of-function effect on the insect-resistant varieties in the future.…”

Efficacy and Cost-Effectiveness of Phenotyping for Rice Resistance and Tolerance to Planthoppers

“…The Ovipostion 20.2 ḟ/m test also indicated relatively low egg-laying on the same resistant plants. However, a recent, detailed study of oviposition in planthoppers indicates that much of the egg load of females is derived from the host on which the female develops, with subsequent egg-laying cycles determined by the food acquired during oviposition [ 57 ]. For example, in our oviposition test, the females were reared on TN1 before transfer to test lines and were therefore capable of laying large numbers of eggs during an initial oviposition cycle, even on the resistant varieties.…”