Feeding Preference Of Altica Deserticola For Leaves Of Glycyrrhiza Glabra And Glycyrrhiza Uralensis And Its Mechanism

The roots and rhizomes of Glycyrrhiza glabra L.and Glycyrrhiza uralensis Fisch are important traditional Chinese medicines in China.Artificial cultivation of licorices effectively alleviated the contradiction between market supply and demand caused by the sharp reduction of wild licorices resources.However,insect pests during intensive production have caused a decline in the yield and quality of artificially cultivated licorices.Altica deserticola(Coleoptera: Chrysomelidae)is a monophagous insect that feeds on the leaves of licorices and is a harmful insect of licorice.Both adults and larvae feed on the leaves of licorices,which will cause great economic losses when the pest is severe.Field investigation showed that the flea beetle seemed to be more inclined to feed on G.uralensis population than G.glabra population.However,due to the different habitats of the two populations,we can’t confirm whether the difference of leaf feeding choice of flea beetle is caused by the difference of genetic material or the difference of ecological factors between the two populations.Therefore,under strictly controlled conditions,this study explored the preference of A.deserticola to the leaves of G.glabra and G.uralensis in the same habitat,and analyzed the internal mechanism of the preference of A.deserticola to the leaves of G.glabra and G.uralensis from their physical and chemical characteristics.Because the soil water and nitrogen conditions often have significant effects on the physical and chemical properties of plant leaves,we set up four conditions: high water and high nitrogen,high water and low nitrogen,low water and high nitrogen,low water and low nitrogen,and explored the effects of different water and nitrogen management measures on the physical and chemical properties of the two kinds of licorice leaves,and the feeding differences of A.deserticola on the two kinds of licorice leaves under different soil water and nitrogen conditions,in order to explore the relationship between water and nitrogen supply and resistance of licorice leaves to A.deserticola,and to provide scientific basis for reasonable water and nitrogen supply of cultivated licorices and control of A.deserticola.The main results are as follows:The adults and larvae of A.deserticola had the same preference to the leaves of G.glabra and G.uralensis in the same habitat,that is,when G.glabra and G.uralensis grew in the same habitat,both adults and larvae preferred to eat the leaves of G.uralensis,and G.glabra had strong insect resistance.In the same habitat,the hardness,thickness and cuticle thickness of G.glabra leaves were significantly higher than those of G.uralensis leaves.There was no significant difference in water content between high water and high nitrogen(HWHN)and high water and low nitrogen HWLN),but the water content in leaves of G.uralensis was significantly higher than that in leaves of G.glabra under low water and low nitrogen(LWLN)and low water and high nitrogen(LWHN).The nitrogen content in leaves of G.uralensis was significantly higher than that of G.glabra,and the contents of total tannin,tannic acid and catechin in leaves of G.glabra were significantly higher than those of G.uralensis.Compared with G.uralensis,G.glabra has thicker leaves,harder texture and more developed cuticle,which may be one of the reasons why A.deserticola do not like to eat G.glabra leaves.At the same time,the content of tannins in the leaves of G.glabra was higher,and its nitrogen content was lower,which may be another important factor that A.deserticola prefer to feed on the leaves of G.uralensis.Therefore,the interspecific differences of leaf physical and chemical properties may be the internal reason that both adults and larvae of A.deserticola tend to feed on the leaves of G.uralensis.Under low water condition,leaf thickness,cuticle thickness and tannin content decreased significantly with the increase of soil nitrogen,while nitrogen content increased significantly.Under high water condition,the total tannin content,catechin and ellagic acid content in leaves decreased significantly with the increase of soil nitrogen,while the leaf thickness and tannin content increased with the increase of soil nitrogen.Under low nitrogen condition,leaf thickness,cuticle thickness,total tannin content and four tannins content decreased with the increase of soil moisture,while nitrogen content increased with the increase of soil moisture.Under high nitrogen condition,leaf thickness,total tannin content,catechin and ellagic acid content increased with the increase of soil water content,while nitrogen content and tannin content were on the contrary.Therefore,we believe that the physical and chemical characteristics of licorices leaves are shaped by their own genetic factors and environmental factors.The adults and larvae of A.deserticola had significant preference for the leaves of G.glabra and G.uralensis under LWHN treatment.The reason may be that the leaves of licorices under this treatment are relatively soft and thin,rich in nitrogen and low in tannins.In conclusion,A.deserticola has a preference for G.glabra leaves and G.uralensis leaves,which is affected by the physical and chemical characteristics of licorice leaves,and the physical and chemical properties of leaves will also change with the changes of environmental factors.Therefore,in the process of intensive production of cultivated licorices,if there is no requirement for cultivated varieties,it is a good choice to plant Glycyrrhiza glabra because of its better resistance.In the cultivation and management,the resistance to low water and low nitrogen(LWLN)treatment was the strongest.Therefore,high level of nitrogen and water supply should be avoided to reduce the feeding harm of Altica deserticola and ensure its yield and quality.