EFFECTS OF CYASTERONE ON GROWTH AND DEVELOPMENT OF DIAMONDBACK MOTH,PLUTELLA XYLOSTELLA (L.)*

Abstract Cyasterone is the main phytoecdysteroid component from cultured plants of Ajuga nipponensis, and common in other Ajuga species. Results showed that when treated with 50 mg/L cyasterone, the egg hatching of diamondback moth was retarded. The total percentage of eggs hatched in treatment was 94.7%, significantly less than that in control, which was 100%. Low toxicity and good antifeeding activity to the 3rd instar larvae were exhibited, which are dependent upon concentration. The growth and development of diamondback moth were affected by cyasterone. It was found that, at concentrations higher than 50 mg/L cyasterone, the larval growth and egg production were inhibited; while promoted at lower concentrations. This dual role of cyasterone might be attributed to its hormonal activity and antifeeding activity, which resulted in poor nutrition. The pupation and eclosion were hindered by treatment of larvae. This insect species was more susceptible to cyasterone than 20‐hydroxyecdysone.     

The effects of ingested ecdysteroid agonists (20-hydroxyecdysone, RH5849 and RH5992) and an ecdysteroid antagonist (cucurbitacin B) on larval development of two polyphagous lepidopterans (Acherontia atropos and Lacanobia oleracea)

Larvae of two polyphagous lepidopteran species, Lacanobia oleracea (Tomato moth) and Acherontia atropos (Death's head hawkmoth), have been treated with representatives of three classes of compounds which are known to interact with the ligand binding site of insect steroid hormone receptors: a steroidal ecdysteroid (20-hydroxyecdysone; 20E; agonist), two non-steroidal dibenzoylhydrazines (RH5849 and RH5992; agonists) and the triterpenoid cucurbitacin B (cucB; antagonist). Both species are unaffected by dietary 20E at concentrations up to 400 ppm. L. oleracea metabolises ingested [³H]20E to a mixture of C-22 fatty acyl esters, while A. atropos excretes [³H]20E unmetabolised. Both species are susceptible to the dibenzoylhydrazines when these are incorporated into the diet, with RH5992 proving lethal at 1 ppm and RH5849 proving lethal at 10 ppm. Thus, the metabolic/excretion mechanisms which are so effective against ingested 20E do not recognise the non-steroidal agonists. The two species showed varying degrees of tolerance to cucB; L. oleracea was unaffected by 400 ppm in the diet, while A. atropos showed effects at 400 ppm, but not at 40 ppm. Feeding cucB in conjunction with 20E or injecting cucB when the ecdysteroid titre was low or rising also had no effect in L. oleracea. It is suggested that tolerance to the two classes of natural products (ecdysteroids and cucurbitacins) is associated with the occurrence of these compounds in some of the host plants of these species; evidence is presented for the presence of phytoecdysteroids in the host plants.     

平卧川牛漆甾酮对小菜蛾生长发育的影响(英文)

平卧川牛漆甾酮是紫背金盘中的主要植物蜕皮甾类 ,在筋骨草属植物中普遍存在。试验结果表明 ,用 5 0mg L平卧川牛漆甾酮处理小菜蛾卵 ,其孵化受到抑制 ,总孵化率为 94.7% ,显著低于对照的 1 0 0 %孵化。平卧川牛漆甾酮对幼虫具有弱的毒杀活性和良好的拒食活性 ,且与浓度相关。小菜蛾的生长发育也受平卧川牛漆甾酮的影响。用高于 5 0mg L浓度处理幼虫 ,其生长受抑及蛾的产卵量下降 ,而较低浓度处理则有利于幼虫生长 ,卵量提高。这种双重作用可能是由于平卧川牛漆甾酮的激素活性和拒食活性的作用结果 ,后者导致昆虫营养不良。处理幼虫后 ,试虫的化蛹和羽化受阻。小菜蛾对平卧川牛漆甾酮比 2 0 羟基蜕皮酮更敏感。     

A phytoecdysteroid,taxisterone, from Taxus cuspidata

A new phytoecdysteroid, taxisterone, was isolated from Taxus cuspidata and the structure was deduced to be 22-deoxyecdysterone by spectral data.