Loop replacements with gut-binding peptides in Cry1Ab domain II enhanced toxicity against the brown planthopper, Nilaparvata lugens (Stål)
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Abstract Bacillus thuringiensis (Bt) Cry toxins have been used widely in pest managements. However, Cry toxins are not effective against sap-sucking insects (Hemiptera), which limits the application of Bt for pest management. In order to extend the insecticidal spectrum of Bt toxins to the rice brown planthopper (BPH), Nilaparvata lugens , we modified Cry1Ab putative receptor binding domains with selected BPH gut-binding peptides (GBPs). Three surface exposed loops in the domain II of Cry1Ab were replaced with two GBPs (P2S and P1Z) respectively. Bioassay results showed that toxicity of modified toxin L2-P2S increased significantly (~9 folds) against BPH nymphs. In addition, damage of midgut cells was observed from the nymphs fed with L2-P2S. Our results indicate that modifying Cry toxins based on the toxin-gut interactions can broaden the insecticidal spectrum of Bt toxin. This method provides another approach for the development of transgenic crops with novel insecticidal activity against hemipteran insects and insect populations resistant to current Bt transgenic crops.Keywords:
Brown planthopper
Bacillus thuringiensis
Abstract The virulence change and damage characteristics of brown planthopper (BPH), Nilaparvata lugens Stal, populations collected from Guangxi, Yunnan and Zhejiang Provinces were studied by using various resistant rice varieties. The results indicated that the Zhejiang population could successfully infest varieties IR26 and Mudgo, showing the characters of BPH biotype 2 after 1989. The Guangxi population, however, could adapt the resistant varieties IR26, Mudgo and ASD7 after 1991. In 1997, the nymphal survival indices of Guangxi and Yunnan populations on Rathu Heenati ( Bph3 ) were up to 70. 9 and 66. 7 respectively. This may imply that the BPH populations in Guangxi and Yunnan have shifted into a new biotype. In free‐choice test, there was obvious difference in the feeding preference of nymphs and adults of Zhejiang population, the adult preferred to feeding on resistant variety IR26 and the nymphs chose the hosts randomly. Under 26 C and L12: D12, the nymphal duration of Zhejiang population was the longest in the three tested populations. For Guangxi population, the nymphal duration on ASD7 was significantly longer than on TN1, although it could infest resistant variety ASD7. The nymphal survival rate of Zhejiang population fed on IR26 was higher than those fed on TN1 and ASD7. On varieties IR26 and ASD7, an obviously higher nymphal survival rate was observed in Yunnan population as compared to those of Zhejiang and Guangxi populations. These results indicate that difference in virulence and damage characteristics could be found in different geographical populations of BPH.
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Studies were undertaken to evaluate the rice genotypes of Sikkim and Tripura for their resistance against brown planthopper (BPH) under glasshouse conditions.Among 74 rice genotypes phenotyped, a genotype (AC-39843) was considered as resistant and two other genotype (AC-39842 and AC-39877) of Tripura were categorized as moderately resistant to BPH.To understand their mechanism of resistance, resistant genotypes were evaluated for different parameter of antixenosis and antibiosis.The antixenosis and antibiosis studies in terms of nymphal setting preference, per cent unhatchability of eggs, nymphal survival and development, honeydew excretion, probing mark test, plant dry weight loss and defence enzymes (Peroxidase, polyphenol oxidaseand catalase) indicated that these genotypes showed confirmation of resistance to BPH compared to susceptible check TN 1.Among resistant genotypes, AC-39843 recorded lowest sugar content followed by AC-39842 and AC-39877 compared to TN1.Total phenol content in AC-39843 was highest followed by AC-39877 and AC-39842.Resistant genotypes found in the study could be used as new resistant donors and utilized in resistance breeding programme against brown planthopper in rice.
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Twelve commercial insecticides in EC and WP forms at 0.025, 005, 0,075 and 0.10% ai, were evaluated against adults and nymphs of BPH separately using diazinon 0.05% as standard. Considering the overall persistent toxicity against adults and nymphs based on 'PT values and overall mean persistent toxicity, chlorpyrifos and carboturan 0.05% 1 as foliar sprays followed by quinalphos and monocrotophos are the most effective in the control of BPH in the field.
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In this paper,the biotypes of brown planthopper were determined by population and individuals.The results showed that the biotypes in the fields turned into Biotype 3 from Biotype 1 and 2,and we should pay high attention to the increasing of Biotype 3 for its strong destructivity.
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Delphacidae
Brown rice
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The brown planthopper, N. lugens, is not able to develop well at 35℃. Previous investigation showed that 35℃-treated N. lugens harbored fewer symbionts than untreated ones, and it was suggested that symbiont played an important role in nutritional metabolism. Nevertheless.
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Delphacidae
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1) トビイロウンカの雌においては,飼料あたりの虫数が少い場合に短ばね型出現率が高くなり,空間あたりの集合は短ばね型出現を抑制していない。ヒメトビウンカの雌では飼料あたりの虫数が少ないことが短ばね型出現の第一条件であるが,空間あたりの虫数が多いことによって短ばね型出現が抑制される。トビイロウンカの雄においては空間あたりの集合が短ばね型出現を促進するが,飼料あたりの集合はこれを抑制する。ヒメトビウンカの雄の短ばね型は著者の行なった実験方法ではごくまれにしか出現しなかった。2) 衰弱した芽出しイネでの単独飼育では両ウンカとも雌も雄も短ばね型の出現が全くないか,ごくわずかであった。3) ヒトメビウンカにおいて管壁を隔てての視覚による相互認識がはね型に影響するという証明は得られなかった。4) 幼虫の芽出しイネ上での分布の仕方は,両ウンカとも1令のみに同一芽出しイネへの集中性が見られた。
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This study was carried out to identify a high-resolution marker for a gene conferring resistance to brown planthopper (BPH) biotype 1, using japonica type resistant lines. Bulked segregant analyses were conducted using 520 RAPD primers to identify RAPD fragments linked to the BPH resistance gene. Eleven RAPDs were shown to be polymorphic amplicons between resistant and susceptible progeny. One of these primers, OPE 18, which amplified a 923 bp band tightly linked to resistance, was converted into a sequence-tagged-site (STS) marker. The STS marker, BpE18-3, was easily detectable as a dominant band with tight linkage (3.9cM) to Bphl. It promises to be useful as a marker for assisted selection of resistant progeny in backcross breeding programs to introgress the resistance gene into elite japonica cultivars.
Brown planthopper
Bulked segregant analysis
Sequence-tagged site
Molecular marker
Marker-Assisted Selection
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(Esaki & Hashimoto) is a common parasitoid of the most important rice pest, the brown planthopper (BPH)
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Brown planthopper
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1. 九州農試育成のトビイロウンカ抵抗性系統西海165号,西海168号及び関東 PL 4における抵抗性現象の解析と,ほ場における生息密度抑制効果を明らかにした。2. 抵抗性系統では,幼虫の発育がやや遅延するが成虫の羽化及び成虫の生存に対しては顕著な抗生作用を示さなかった。3. 抵抗性系統では,産卵数が感受性品種の1/2～1/4であった。4. 抵抗性系統は,トビイロウンカに対して顕著な非選好性を示した。5. ほ場におけるトビイロウンカの生息密度は,各世代とも抵抗性系統では「あそみのり」に比べ明らかに低く,顕著な生息密度抑制効果を示した。これは飛来侵入期における抵抗性系統の非選好性による発生源の減少と産卵数を減少させる抗生作用及びその他の環境要因が関与しているものと思われる。6. 西海165号,西海168号,関東PL4は,同様の抵抗性機作及び抵抗性程度を持っているものと思われる。
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Brown rice
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