寄主挥发物、叶色和表皮毛在美洲斑潜蝇寄主选择中的作用

Effects of host volatiles, leaf color, and cuticular trichomes on host selection by Liriomyza sativae Blanchard

在室内条件下 ,初步研究了寄主挥发物、叶色和表皮毛在美洲斑潜蝇寄主选择中的作用。在嗅觉仪试验中 ,寄主叶片挥发物对美洲斑潜蝇雌成虫没有明显的引诱作用 ;在叶色反应试验中 ,美洲斑潜蝇雌成虫在叶子圆片上停留的时间明显大于在滤纸圆片上停留的时间 (p<0 .0 1) ,其在有叶片区域分布的数量明显多于空白对照 (p <0 .0 1) ;在表皮毛试验中 ,美洲斑潜蝇在无毛叶片上的产卵量明显大于在有毛叶片上的产卵量 (p <0 .0 1)。上述结果表明 ,在对寄主的定向和定位过程中 ,美洲斑潜蝇的视觉起着重要的作用 ,而嗅觉不起作用 ;

The serpentine leafminer, Liriomyza sativae Blanchard, is one of the most serious worldwide pests of a great variety of vegetables and ornamental crops. It was first recorded in China in the Hainan province in 1993. Since then it has spread to the most regions of China, and it has attacked a wide variety of crops causing great economic losses. Previous studies have shown that the leafminer has different preferences for host plants. The mechanism on its host selection, however, is so far unknown. In this paper, the role of host volatiles, leaf color, and cuticular trichomes of host plants for host preference of the leafminer were studied in the laboratory. A four-armed olfactometer was used to test the role of volatiles from host plants in host selection by the leafminer. One of the four arms was connected to the odor source of kidney bean leaves and the other three arms were connected to blank controls. The time spent by L. sativae adult females in the different areas of the olfactometer; each corresponding to one of the four odor sources was recorded and 30 females were tested in total. The results showed that although the time of the females in each of areas was significantly different (p<0.05) , the time spent by the females in the area linked to the arm with the odor of kidney bean leaves was not always the longest. In another experiment, ten females were introduced into the olfactometer chamber simultaneously and the of the females remaining in each area of olfactometer was recorded once every 5 minutes for 30 minutes, and totally 100 females were tested. The number of females recorded in the different areas did not differ significantly (p>0.05). These results indicate that the volatile compounds emitted from kidney bean leaves do not play an important role in host selection by the leafminer. To test the role of leaf color in host preference of the leafminer, a Petri dish (15 cm in diameter) was used in which a kidney bean leaf disc (4 cm in diameter) sealed with transparent film to prevent odor release was placed on one side and the other side was a piece of filter paper with the same size as the leaf disc. One female leafminer was released into the container and the time spent by the leafminer on the leaf disc or the paper was recorded continuously for 10 minutes, and 30 leafminers were tested. The results showed that the time spent by the leafminer on the kidney leaf disc was much longer (p<0.01) than that on the filter paper. In another experiment, four small flasks, one with a kidney bean leaf and the others with nothing in them as blank controls, were put into one of four corners of a square container (80×80×15 cm^3). Ten females were introduced into the container each time and the number of the females in each corner of the container was recorded every 5 minutes for 20 minutes. One hundred females were tested. It was found that the number of the females present in the corner with bean leaves was much more (p<0.01) than that in the other three corners with empty flasks. A cucumber variety with hairy leaves was chosen to test the role of cuticular trichome of host plants in host preference of the leafminer. Three pairs of cucumber leaves (one normal leaf with cuticular trichomes and the other a control leaf from which the cuticular trichomes had been carefully removed with a forceps) were placed into a container (15 cm in diameter) and two pairs of the female and male were introduced. The number of eggs laid by the leafminer on the normal cucumber leaves and the control leaves was recorded after 24h, respectively. The results revealed that the number of the eggs was much less (p<0.01) on the normal leaves than on the control leaves. It was concluded that the physical characteristics of the host plants, leaf color and trichomes, play an important role in the host preference of L. sativae, while the volatile compounds emitted from host plants do not.