Preference Assessment of White-backed Planthopper Feeding on Rice
Summary
This study presents a simple and feasible method to assess the nonpreference resistance to white-backed planthoppers who are feeding on rice under laboratory conditions. Improvement of the strategies and makeup of the current method of identification of the resistance to white-backed and brown planthoppers are discussed.
Abstract
Exploiting insect-resistant rice germplasm resources and related genes is the primary need for breeding insect-resistant varieties, but the accuracy of the identification of insect-resistant phenotypes of rice is a major difficulty. It is urgent to develop a new method or improve existing methods to screen rice for insect resistance. This article describes a simple and feasible method to assess nonpreference-type resistance of rice to the white-backed planthopper (WBPH), Sogatella furcifera, in the laboratory. The preference of adult WBPHs feeding or inhabiting on maturing rice plants is continuously analyzed by pairwise comparison. The dynamic changes of WBPHs on rice plants are recorded and compared as an index of resistance identification. The current method is simply operable and easily observable and has a short cycle. The use of this method could be extended to investigate the feeding and oviposition preference of similar hemipterans, such as the brown planthopper (BPH), Nilaparvata lugens(Stål).
Introduction
Rice is a staple food for over one-third of the world's population, and more than 90% of rice is produced and consumed in Asia1,2. The WBPH and BPH are the most destructive pests of rice and a substantial threat to rice production3. From the perspective of cost and environment, the breeding and application of insect-resistant rice is the most effective approach to control the damage caused by planthoppers4,5,6. Accordingly, the screening of resistant rice germplasm resources is a key prerequisite for breeding insect-resistant rice. The accuracy in the identification of rice-resistant phenotype is helpful for fine mapping and further functional research of target genes. However, phenotypic identification has become a major difficulty due to the complexity of the resistance mechanism. Rice's resistance to pests can be divided into three types, namely antibiosis, tolerance, and nonpreference7. Each type reflects a different aspect of the resistance mechanism of rice to pests. At present, the most widely used method of screening for resistance to planthoppers is the standard seedbox screening technique (SSST) which can be used to quickly identify the phenotypic resistance of a large number of rice plants and to obtain candidate resistant germplasm lines in a short time8.
However, the SSST method only reflects the resistance of rice at the seedling stage and is more effective in assessing tolerance-type resistance mechanisms. Rice's resistance to insects is also reflected in antibioses, such as nymph survival rate, nymph duration, and egg hatching rate, and in nonpreference, such as habitat, feeding, and oviposition preference9. In addition, the performance of rice seedlings for resistance is often not very stable. With the growth of plants, resistance tends to become more stable. Therefore, the SSST method cannot completely reflect the resistance level of rice. Moreover, rice's resistance to pests varies at different growth stages, and there are obvious differences in resistance mechanisms between seedling and maturing plants. Studies have shown that maturing rice plants can release volatile secondary metabolites to avoid infestation by insect pests, which are manifested by the insect's nonselectivity in feeding or oviposition on the rice plant10,11. This is also a very critical kind of resistance mechanism, which plays an important role in preventing insect pests and ensuring rice yield at maturity.
At present, the identification of rice's resistance by nonpreference is still a challenge. In this case, two main approaches are currently used. On the one hand, planthoppers and rice plants are put in a square nylon net cage12. Although this approach is considered to be relatively efficient for carrying out experiments on multiple rice lines simultaneously, it requires a larger experimental space and, thus, causes some difficulties in observation and counting due to nontransparent nylon net materials. On the other hand, the Y-tube olfactometer method is used in insect selection experiments according to the difference in volatile substances released from rice. This method facilitates easy observation because of its glass container14. One of the major limiting factors of this method is that it can only judge volatile smell, and it also has a strict requirement on the tightness of the experimental devices and takes a long time.
Herein, we describe an improved method for evaluating the nonpreference-type resistance of the rice plant to WBPHs, which is simple to operate and easy for observation. This method can also be used to study the habitat, feeding, and oviposition preference behavior of BPHs and other hemipterous pests.
Protocol
Representative Results
Discussion
Maturing rice plants release volatile secondary metabolites to control insect pests or reduce the mating capacity of these pests (such as in WBPHs) via a special physical structure on the leaf sheath surface, which is a key resistance mechanism13. In rice plants, the nonpreference is not only related to feeding but also associated with habitat and mating. However, current studies have focused on the nonpreference of nymphs4,12, and a new m…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors are grateful to Dr. Lang Yang for feeding the white-backed planthoppers and culturing rice. This work was supported by Special Funds for the Industrial Development of the Dapeng New District, Shenzhen City (Grant No. KY20180216 and KY20180115).
Materials
| climate-controlled room | Ningbo Jiangnan Instrument Factory | SZJYS2013 | temperature, relative humidity, photoperiod control |
| glass tube with sponge stopper | / | / | diameter 2 cm and height 15 cm |
| handmade suction trap | / | / | / |
| insect-proof cage | / | / | 200-mesh, (L × W × H, 75 × 75 × 75 cm) |
| Nylon net | / | / | 200 mesh |
| paddy soil | / | / | / |
| plastic seed box | / | / | (L × W × H, 20 × 15 × 10 cm) |
| plastic seed pot | / | / | 10-cm-diameter |
| plastic tray | / | / | (D × H, 28 × 10 cm) |
| rice seed of FY01 line | / | / | 60 seeds |
| rice seed of HZ06 line | / | / | 30 seeds |
| rice seed of HZ08 line | / | / | 30 seeds |
| rice seed of TN1 variety | / | / | many |
| Rubber band | / | / | diameter is 1.5 mm, and the circumference is 32 cm |
| scotch tape | / | / | / |
| SPSS Statistics 19.0 | IBM Corporation | / | statistical data analysis |
| stapler | / | / | / |
| transparent PVC | / | / | 120 cm × 90 cm dimensions and thickness of 0.5 mm |
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