RESUMO
Although rice resistance plays an important role in controlling the brown planthopper (BPH), Nilaparvata lugens, not all varieties have the same level of protection against BPH infestation. Understanding the molecular interactions in rice defense response is an important tool to help to reveal unexplained processes that underlie rice resistance to BPH. A proteomics approach was used to explore how wild type IR64 and near-isogenic rice mutants with gain and loss of resistance to BPH respond during infestation. A total of 65 proteins were found markedly altered in wild type IR64 during BPH infestation. Fifty-two proteins associated with 11 functional categories were identified using mass spectrometry. Protein abundance was less altered at 2 and 14 days after infestation (DAI) (T1, T2, respectively), whereas higher protein levels were observed at 28 DAI (T3). This trend diminished at 34 DAI (T4). Comparative analysis of IR64 with mutants showed 22 proteins that may be potentially associated with rice resistance to the brown planthopper (BPH). Ten proteins were altered in susceptible mutant (D1131) whereas abundance of 12 proteins including S-like RNase, Glyoxalase I, EFTu1 and Salt stress root protein "RS1" was differentially changed in resistant mutant (D518). S-like RNase was found in greater quantities in D518 after BPH infestation but remained unchanged in IR64 and decreased in D1131. Taken together, this study shows a noticeable level of protein abundance in the resistant mutant D518 compared to the susceptible mutant D1131 that may be involved in rendering enhanced level of resistance against BPH.
RESUMO
Varietal mutants can be useful for developing durable resistance, understanding categories of resistance, and identifying candidate genes involved in defense responses. We used mutants of rice 'IR64' to isolate new sources of resistance to the planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). We compared two mutants that showed a gain and loss of resistance to N. lugens, to determine the categories of resistance to this pest. Under choice tests, female planthoppers avoided settling and laid fewer eggs on the resistant mutant 'D518' than on the susceptible mutant D1131, susceptible check 'TN1', and wild-type IR64, indicating that antixenosis was the resistance category. Similarly, under no-choice conditions, planthoppers laid 29% fewer eggs in D518 than in IR64, but they oviposited more in 'D1131' and TN1. Honeydew excretion was greater on D1131 seedlings but slightly lower on D518 than on IR64. Nymphal survival and adult female weight did not differ among rice cultivars. D518 showed higher tolerance of N. lugens infestations than IR64. Genetic analysis of the F1, F2, and F3 populations derived from D518 x IR64 revealed that resistance in D518 is dominant and controlled by a single gene. Despite the variation in resistance to N. lugens, both mutants and IR64 performed similarly in the field. The mutant D518 is a new source of durable resistance to N. lugens, mainly due to enhanced antixenosis to female hoppers for settling and oviposition.