Impacts of nitrogen fertilizer on major insect pests and their predators in transgenic Bt rice lines T2A‐1 and T1C‐19

Abstract

Nitrogen is a critical factor for plant development and nitrogen input is one of the important tactics to enhance the development and yield of crops. Nevertheless, nitrogen input could influence the occurrence of insects positively or negatively. Nitrogen is also one of the main elements composing the insecticidal crystal (Cry) protein. Cry protein production could affect nitrogen partitioning in Bt plants and as such nitrogen input may influence insect pest management in transgenic Bt rice, Oryza sativa L. (Poaceae). To test this possibility, we evaluated the impacts of nitrogen regimes on the main insect pests and their predators on two Bt rice lines, T2A-1 and T1C-19, expressing Cry2A and Cry1C, respectively, and their non-transgenic parental counterpart MH63. The results showed that Cry proteins with different nitrogen regimes have enough insecticidal activity on rice leaffolder, Cnaphalocrocis medinalis Guen ee (Lepidoptera: Crambidae), in both laboratory and field experiments. Laboratory studies indicated that relevant parameters of ecological fitness in brown planthopper, Nilaparvata lugens (St al) (Hemiptera: Delphacidae), a non-target insect pest, were significantly affected by nitrogen input both on Bt and MH63 rice lines. Nymphal survival, female adult longevity, and egg hatchability in N. lugens differed significantly among rice varieties. The experiments conducted in rice fields also demonstrated that nitrogen was positively correlated with the abundance of N. lugens on Bt rice, similar to that on MH63 rice. The abundances of two predatorsthe wolf spider Pirata subpiraticus (Boesenberg & Strand) (Araneae: Lycosidae) and the bug Cyrthorhinus lividipennis Reuter (Hemiptera: Miridae)were significantly affected by rice growth stages but not by nitrogen input and rice varieties. In conclusion, the above results indicate that high nitrogen regimes for Bt rice (T2A-1 and T1C-19) and non-Bt rice (MH63) cannot facilitate the management of insect pests.

Immune Responses and Transcriptomic Analysis of Nilaparvata lugens against Metarhizium anisopliae YTTR Mediated by Rice Ragged Stunt Virus

“…It was reported that some of the pesticides have a promotion role in the fecundity and development of BPH, which will accelerate its outbreak of the pest in the field [ 3 , 5 , 6 ]. Moreover, other irrational agronomic practices, such as the irrational use of nitrogen fertilizer, made the control of BPH even more challenging [ 2 , 7 ].…”

Cry1C rice doesn’t affect the ecological fitness of rice brown planthopper, Nilaparvata lugens either under RDV stress or not

“…The effects of Bt rice on NTAs including herbivores, predators, parasitoids and detritivores have been studied thoroughly in past 20 years 27 . Recently, much attention has been paid to effects of Bt crops on indirect multi-trophic interactions, whereas few attentions were paid to the combined effects of Bt rice with other biotic or abiotic factors 13 – 15 , 18 , 19 , 28 – 31 . Interactions between plants and pathogens on insects are complex.…”

Elevated CO2 alters transgene methylation not only in promoterregion but also in codingregion of Bt rice under different N-fertilizer levels

“…Bruns and Abel reported that the Bt protein production of two transgenic Bt -transgenic maize lines increased with the augmentation of N fertilizer application 41 . Yang et al found that the contents of Cry2A and Cry1C in Bt rice both increased in the tillering and milking stages with the higher N concentrations applied on rice 42 . Wang et al documented that the Cry1Ab/1Ac content of Bt -SY63 at higher N fertilizer was significantly higher than that without N fertilizer treatment 43 .…”