Electrophysiological And Behavioral Responses Of Bees To The Volatiles Compounds Of Pear Flowers

Bees and angiosperms have shared a long and intertwined evolutionary history and their interactions have resulted in remarkable adaptations.Bees search for the source of honey and nectar plants through vision and olfactory.As long-distance signals to attract pollinators,floral scents provide unique chemical characteristics for flowers,which affect the foraging preference of pollination insects.Pear is one of the problematic crops that bees did not like to foraging,it may be related to the color,aroma and pollen nutrition of pear flowers.In this study,pear flower compounds were determined by GC-MS.The volatile compounds with strong chemotaxis to pear flowers were screened out by electroantennogram(EAG)and three-arm Olfactometer(behavioral study),and the reasons for bees reluctance to collect pear flowers were explored from the perspective of volatile compounds.The main results are as follows:(1)Volatile compounds in pear flowers of Pyrus bretshneideri Dangshan pear,Pyrus bretshneideri Ya pear and Pyrus bretshneideri Xuehua pear were determined by GC-MS,respectively.The results of GC-MS showed that 51 kinds of volatiles compounds in Dangshan pear flowers were alcohols,phenols,ketones,hydrocarbons,terpenes,esters and aldehydes.The first five compounds with high relative content were 3-Methyl-1-butanol,(+)-limonene,2-phenylethanol,tridecane and nonanal;the Xuehua pear contain 42 kinds of volatile compounds,including alcohols,ethers,ketones,hydrocarbons,terpenoids,esters and aldehydes,and the first five substances with relatively high content are 3-methyl-1-butanol,(+)-limonene,dimethyl thioether,tridecane and nonanal,respectively;the volatiles compounds of Ya pear flowers are alcohols,ethers,ketones,hydrocarbons,terpenoids,aldehydes and acids,total of 41 kinds.The first five substances with high relative content are(+)-limonene,3-methyl-1-butanol,DL-Gabaculine,dimethyl sulfide and methyl isovalerate.(2)The EAG responses of Apis cerana cerana and Apis mellifera ligustica to volatiles compounds of pear flowers.The results showed that the EAG responses of Apis cerana cerana and Apis mellifera ligustica to 1-Octen-3-ol,2-Methylbutyraldehyde,3-methyl-1-butanol,6-methyl-5-heptene-2-one,1,4-Xylene,?-farnesene and nonanal increased with the concentration.The EAG responses of Apis cerana cerana to 1-Octen-3-ol,2-Methylbutyraldehyde,3-methyl-1-butanol,6-methyl-5-heptene-2-one and nonanal at different concentrations were significantly different.EAG responses of 1-nonanol,dodecane,tridecane,linalool and tetradecane decreased with increasing concentration;EAG response of Apis mellifera ligustica to 3-methyl-1-butanol,2-Methylbutyraldehyde,6-methyl-5-heptene-2-one 1,4-Xylene,?-farnesene,dodecane,tridecane,tetradecane and nonanal increased with increasing concentration;of which 1-octene-3-butanol,2-Methylbutyraldehyde and nonanal EAG responses increased.The EAG response of 1-Octen-3-ol,2-Methylbutyraldehyde,3-methyl-1-butanol,6-methyl-5-heptane-2-one and nonanal at different concentrations were significantly different.The EAG response of linalool decreased with the increase of concentration,EAG response of Apis cerana cerana and Apis mellifera ligustica to Diisobutyl phthalate was lower and the response to 1,4-Benzoquinone was extremely strong at 400 ?g/?L concentration.(3)The results of behavioral studies on volatile compounds showed that Apis cerana cerana showed a significant avoidance response to 1-Octen-3-ol,6-methyl-5-heptene-2-one,nonanal and 2-methylbutyraldehyde.The attraction rate of 3-methyl-1-butanol to Apis cerana cerana was the highest(43.33%).Apis mellifera ligustica showed significant aversion to 6-methyl-5-hepten-2-one,nonanal,1-Octen-3-ol and ?-farnesene.The attraction rates of 3-methyl-1-butanol and 2-methylbutyraldehyde to Apis mellifera ligustica were the highest(36.67%).Compared with Apis mellifera ligustica,Apis cerana cerana has more evident avoidance response to nonanal,1-Octen-3-ol,6-methyl-5-hepten-2-one and 2-methyl butyraldehyde.