Regulation Of Floral Scent Of Greenhouse Tomato On The Foraging Behaviors Of Bee Pollinators

Floral scents usually play an important role in bee pollinator-flowering plant coevolution system.Both innate biase and prior learned expriences infuenced bees foraging behaviors.Honeybee and bumblebee are widely used pollinators in agriculture,which can improve crops production and quality significantly.Compared with bumblebee,honeybee is less attracted to tomato flowers and has lower pollination efficiency in tomato.Little is known about how tomato floral scents regulates the foraging behaviors of these two bee species.In the current study,we investigated the foraging behaviors of honeybee Apis mellifera and bumblebee Bombus lantschouensis on tomato flowers and determined whether honeybee and bumblebee show different responses to tomato floral scent.The main results were as follows:1.Foraging behaviors of different bee pollinators on greenhouse tomato.The daily pattern of the number of outgoing and ingoing foragers,visitor density and pollen collecting behaviors of honeybee and bumblebee on tomato flowers were investigated.Significant differences were found in foraging behaviors of honeybee and bumblebee on tomato.More bumblebee foragers going out of hives(F_{2.340,124.041}=4.042,P=0.015)and visited tomato flowers(F_{2.606,416.955}=18.648,P<0.000)than honeybee foragers and the proportion pollen collecting foragers in bumblebee was much higher than honeybee(F_1,53=80.216,P<0.000).Fewer honeybee foragers visited tomato flowers in greenhouses and the number of outgoing foragers(F_1,3=18.58,P=0.04)and flower visitors(F_1,3=91.518,P=0.01)decreased significant during tomato flowering period.2.Behavioral responses of bee pollinators to tomato floral scent.The influences of innate biase and prior learned expriences on bees'behavioral choice towards tomato floral scent were invetigated.The results showed that the scent learning experiences with food reward could change the innate bias of bees Both bee species showed aversion to tomato floral scent in a Y-tube olfactometer,and na?ve honeybees showed significant aversion(?²=4.829,P=0.028).However,foraging experience in tomato greenhouses helped bumblebees develop a strong preference for the scent(?²=6.400,P=0.011),whereas honeybees with foraging experience showed continued repulsion by tomato floral scent(?²=4.800,P=0.028).After learning to associate tomato floral scent with a sugar reward in PER assays,both bee species developed a preference for tomato floral scent in Y-tube olfactometers.Compared with that of bumblebees,honeybees show significantly higher learning scores during the learning trials(F_1,800=4.950,P=0.026)and significantly greater memory retention(F_1,240=10.169,P=0.002).3.Influences of tomato floral scent on bees foraging behaviors in tomato greenhouses.The influences of tomato floral scent-food reward learning experiences inside A.mellifera colony on bees foraging behaviors were evaluated.The results showed that scent-learning experiences in honeybee colonies could improve foragers foraging activities.Both the number of outgoing foragers(F_1.507,87.409=88.847,P=0.000)and visitor density(F_{1.806,321.425}=21.137,P<0.000)increased significantly in honeybee colonies with scent-learning experiences;however,the foraging activities decreased with time significantly during tomato flowering period.4.Influences of floral scent and food reward on bee pollinators foraging preferences among different tomato cultivars.The influences of floral scent and pollen quantity on bumblebee B.lantschouensis foraging behaviors among four tomato cultivars were evaluated.The resluts showed that floral scent played a critical role in making foraging decisions when bees facing more than one of food resources choices.Significant bumblebee visitor density(H=18.717,P<0.000)and pollination level(?²=41.997,P<0.000)were found among the four tomato cultivars.Compared with other three cultivars,more less bumblebees visited cultivar‘Jingdanxiaohuangyu'.Pollen quantity(H=45.573,P=0.000)and floral scent composion(F_3,14=1.716,P=0.0032)differed in these tomato cultivars.The pollen quantity in cultivar‘Jingdanxiaohuangyu'and‘Qianxi'were lower than the cultivars of‘Piangguoqing'and‘Zhefen'.By analyzing floral scent composition of the four cultivars,we found that the floral scents of‘Jingdanxiaohuangyu'differed significantly from other three cultivars.In Y-tube olfactometer,na?ve bumblebee showed repulsion by floral scents of‘Jingdanxiaohuangyu',whereas no obviously bias was found for other three cultivars.The floral scents of‘Jingdanxiaohuangyu'contained the EAG-active compound,isophorone,which had a obviously repellent effect on bumblebee(?²=5.565,P=0.018).In summary,the current study showed that bee pollinators could develop a preference for floral scent once they learned to associate the floral scent with a food reward on the basis of foraging experience or scent-learning procedures,which could be utilized to improve bees pollination service efficiency for commercial crops.The results helped to better understand the chemical ecology function of floral scent in bee pollinator-flowering plant coevolution system and provided new method in improving crop bee pollination technology.