Effects Of Photoperiod, Nutrition And Plant Volatile On The Biological Characteristic Of Adult Diamondback Moth, Plutella Xylostella

Diamondback moth (DBM), Plutella xylostella, is one of the important pests in cruciferous vegetables. The larvae cause damage to host plant and adults are mainly feed on water, honey and other nutriments. DBM experiences a short-time life cycle including emergence, feeding, calling, mating, oviposition and other important biological processes. Photoperiodic, volatiles from the host plant and nutriments are important ecological factors to affect the biological characteristics of DBM. The eclosion rhythm of DBM adult under different photoperiod, the host tropism of adults affected by different nutriments, the mating behavior and the synthesis of sex pheromone in adults exposed to different plant volatiles were explored in this study. The main results are as follows1. Effect of photoperiod on eclosion rhythm of DBMDBM adults emerged throughout the day, and the female emerged mainly in dark period, while the male emerged mainly in the light period. When the light and dark period was changed, the emergence rhythm was changed subsequently.2. Effect of nutriments on olfactory behavior, EAG response and fecundityAttraction of allyl isothiocyanate to DBM females which were fed on different nutriments was increased significantly, but there was no significant difference among different nutriment treatments. It was also found that nutrient supplement did not affect the EAG response of male moths to the sex pheromone. The fecundity of female feeding on nutrients was significantly higher than the female feeding on distilled water, and the female feeding on honey solution showed the highest fecundity. DBM started to oviposit from the day of emergence, and the fecundity of the female feeding on honey solution, distilled water or sucrose solution reached the peak on the 3rd day after emergence, and the fecundity of female feeding on brown sugar solution reached the peak on the 2nd day. The oviposition periods of females feeding on honey solution, sucrose solution, brown sugar solution and distilled water were 11 d,12 d, 13 d and 7 d, respectively.3. Effect of plant volatile on mating rhythm and mating duration of DBMAfter DBM was exposed to ally] isothiocyanate, the mating peak was advanced. There was no significant difference in the mating rates between the treatment group and control group, except that the mating rate at 21:00 was lower in the treatment group than in the control group. The mating behavior was observed at 7:00 and 8:00 in the treatment group, but not in the control group. The mating peak was advanced to the first day of eclosiou in the treatment group, which was the second day of etlosion in the control group.After DBM was exposed to allyl isothiocyanate, the mating duration of 5-d adults decreased significantly, but increased significantly on the 7-d adults. The mating duration of 6-d adults and 7-d adults were significantly longer than 1-d and 3-d adults, while in the control group, the mating duration of 5-d and 6-d adults were significantly longer than 1-d adults.4. Effect of plant volatile on DBM EAG and olfactory behavioral responsesThe EAG responses of DBM males to sex pheromone from females were increased with the concentration of plant volatile increased, but decreased at the highest concentration of 100g·μL-1. After DBM was exposed to cis-3-hexene acetate and cis-3-hexenol separately, the EAG responses of males to sex pheromone were significantly stronger than the control group only at 10 ng·μL-1 of sex pheromone. Olfactory behavior test showed that males exposed to plant volatiles tended to select the sex pheromone.5. Effect of plant volatile on the synthesis of DBM sex pheromoneAfter DBM was exposed to cis-3-hexene acetate, cis-3-hexenol and allyl isothiocyanate separately, the constituent of sex pheromone from 48-h-after-eclosion females was not changed significantly.The PBAN gene was evenly expressed in DBM females within 60 h after eclosion. The relative expression level of PBAN gene was decreased significantly and with a reduction of 58.78% after adults were exposed to cis-3-hexenol; the relative expression level of PBAN gene was of a reduction of 58.24% after adults were exposed to allyl isothiocyanate for 18 h, and a reduction of 71.32% after adults were exposed for 60 h. It was concluded that the volatile treatment could increase the expression of PBAN gene. After adults were exposed to cis-3-hexylene acetate, cis-3-hexenol and allyl isothiocyanate for 48 h separately, the relative expression level of PBAN gene was not significantly changed compared to the control, consistent with the influence of volatiles on the production of sex pheromone.