| Bemisia tabaci (Gennadius) Q-biotype is a disastrous invasive alien pest and it has outbreaked worldwidely in recent years. Because of its wider host range and greater insecticide resistance than B. tabaci B-biotype, its invasion mechanism has been a major concern for scientific research. The Q-biotype was first detected in China in Kunming, Yunnan province in 2003, and then reported in Beijing and Henan province in 2004. Now the Q-biotype has been widely spreaded into north, west, middle and south China such as Shannxi, Gansu, Hunan, Hubei, Shanxi, Shandong, Jiangsu, Guizhou, Guangxi, Fujian and Hainan provinces and municipalities. The Q-biotype has superior capacity to survive at high temperature, its adaption to high temperature stress is one of the most important reasons resulting in its replacement of native species ocuppying the same eclogical niche and development into dominant population. Because B. tabaci Q-biotype often encounters high temperature stress in nature, revealing the tolerance and mechanisms of B. tabaci Q-biotype to high temperature stress is important in monitoring its population dynamics, especially under the trend of global warming. In this study, the development, fecundity and population growth rate of B. tabaci Q-biotype after short-term sub-lethal high temperature exposure at its egg, 1st instar nymph or 4th nypmh instar stage were compared. The spermatogenesis of B. tabaci Q-biotype was also observed to illuminate the potential impacts of ub-lethal heat stress on its adult sex ratio change. The main results are as follows:1. Effects of heat shock temperature and duration on the development and reproduction of B. tabaci Q-biotypeTo reveal the reactions of B. tabaci Q-biotype to heat stress, effects of short-term (1 h, 2 h and 4 h) exposure of B. tabaci eggs to high temperature (37℃, 39℃, 41℃and 43℃) on the survival, fecundity and offspring fitness were studied. Survival from egg to adult and pupal eclosion rate of F0 generation of B. tabaci decreased as heat-shock temperature increased and heat-shock duration extended. After heat shock at 41℃for 1h at egg stage, percentage of female adults was 61.0%. Each heat shock treatment at egg stage did not affect the adult female longevity. Female fecundity decreased as heat-shock temperature increased. Developmental period of eggs and immature at F1 generation was significantly prolonged than the control. There were no significant differences on surival of instar of F1 genenration.2. Effects of heat shock temperature and duration at 1st instar nymph stage on the development and reproduction of B. tabaci Q-biotypeTo reveal the reactions of B. tabaci Q-biotype to heat stress, effects of short-term (1 h, 2 h and 4 h) exposure of B. tabaci 1st instar nymph to high temperature (37℃, 39℃, 41℃and 43℃) on the survival, fecundity and offspring fitness were studied. Survival from egg to adult and pupal eclosion rate of F0 generation of B. tabaci decreased as heat-shock temperature increased and heat-shock duration extended. The percentage of female adults had no significant difference between the all heat shock treatment and the control. Each heat shock treatment at egg stage did not affect the adult female longevity. After heat shock at 37℃for 1h, he average fecundity of female adult (98.5) was significant lower than the ck(117.9). Developmental period of eggs and immature at F1 generation was significantly prolonged than the control. There were no significant differences on surival of instar of F1 genenration. After heat shock at 43℃for 1h, percentage of female of F1 adults generation was 58.6%.3. Effects of heat shock temperature and duration at 4th instar nymph stage on the development and reproduction of B. tabaci Q-biotypeTo reveal the reactions of B. tabaci Q-biotype to heat stress, effects of short-term (1 h, 2 h and 4 h) exposure of B. tabaci 4th instar nymph to high temperature (37℃, 39℃, 41℃and 43℃) on the survival, fecundity and offspring fitness were studied. Survival from egg to adult and pupal eclosion rate of F0 generation of B. tabaci decreased as heat-shock temperature increased and heat-shock duration extended. After the 4th instar exposured at high temperature, the percentage of female adults were significant lower than the ck. Each heat shock treatment at egg stage did not affect the adult female longevity and fecundity. Developmental period of eggs and immature at F1 generation was significantly prolonged than the control. There were no significant differences on surival of instar of F1 genenration. After heat shock at 37℃to 39℃, percentage of female of F1 adults generation was significant higher than the control.4. Spermatogenesis observation of B. tabaci Q-biotypeThe spermatid undergoes transformation, changing from spheroid in shape to an elongated fusiform profile. Testes in the adult are full of spermatozoa and sperm cell.5. ConclusionsThe results suggested that short-term exposure of B. tabaci Q biotype to high temperature at egg and nymphal stage could reduce its development fitness, resulting in decreased survival at F0 generation, decreased adult female longevity and fecundity, and prolonged developmental period at F1 generation. However, its high fecundity at F0 generation and high survival at F1 generation could ensure its population extension. The adaptation of B. tabaci Q-biotype to high temperature stress could help it expansion under the global climate warming. The understanding of the thermal tolerance and performance of B. tabaci Q-biotype is essential to evaluate its geographical extension capacity and improve its control strategies. |
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