Influences Of Leaf Mining Pests On Morphology,Physiology And Biochemistry Of Citrus Leaves

Citrus is an important and characteristic industry in south Ganzhou.Gannan navel orange,Xunwu tangerine,and Nankang sweet orange are famous both at home and abroad.However,there are many citrus insect pests,which have detrimental effects on the quantities and qualities of citrus fruits,thus reduce the income of fruit growers.Young leaves of citrus summer shoots are seriously damaged by leaf mining pests(Phyllocnistis citrella and Podagricomela nigricollis).In this paper taking three major citrus varieties(Newhall navel orange,Gannanzao navel orange and Citrus maxima)for example,we have studied the influences of leaf mining pests on the physiological and biochemical indices,spectral indexes and morphological parameters of citrus leaves,and summarized the influencing mechanism of leaf mining pests on the physiology and biochemistry of citrus leaves.Main results are as follows:1?Impacts of citrus leaf miner Phyllocnistis citrella on physiological indices of Newhall navel orange leaves.The contents of MDA,soluble sugar and soluble protein in mined leaves were significantly higher than those in healthy leaves at both the outer and inner canopy,indicating that leaf mining could make leaf membrane lipid peroxide,but the leaves might improve their resistance to the damage of leaf mining moth by increasing the contents of soluble sugar and soluble protein.2?Impacts of leaf mining on spectral indexes and chlorophyll fluorescence parameters.Nearly all mesophyll cells were eaten by the mining beetle Podagricomela nigricollis,which lead to lower SPAD values in both the mined part and the nearby unmined part of damaged leaves.The values of NDVI and PRI of citrus leaves were heavily affected by leaf mining beetles,only in the mined part of damaged leaves.The fluorescence parameters such as Fo?Fm?Fm/Fo and Fv/Fm were significantly affected,although ABS/RC was still at normal level.It should be noted that,mined leaves might increase ETo/RC to compensate the impacts of mining behaviors on photosynthesis.Although only parts of epidermal cells were eaten by the citrus leaf miners Phyllocnistis citrella,the values of SPAD and PRI were significantly lower than healthy leaves at all branch directions.NDVI values of mined leaves at south and north branches were much lower than of the healthy leaves;while there were no differences between mined leaves and healthy leaves at east and west branches,which may indicate SPAD values were sensitive in different branching directions.leaf mining moth had little effects on the fluorescence parameters of Newhall navel orange,significant impacts only found in Fm?Fm/Fo and Fv/Fm.In general,even if the mining behavior might not destroy mesophyll cells,the synthesis of chlorophyll could be possibly inhibited by mining and then the photosynthesis could be affected.3 ? Impacts of leaf-mining pests on leaf morphology.The mining of the beetle Podagricomela nigricollis had no apparent impacts on leaf morphology of citrus leaves.On the contrary the mining of the moth Phyllocnistis citrella significantly affected the length,width,area,perimeter and shape parameters of citrus leaves.4?Image analyses on leaf mines of different leaf-mining moths.The length of mines were obviously different,and mines of Gracillariidae were longest and those of Nepticulidae were shortest.Most leaf mining moth kept the direction of mining forward and avoid large-angle turning,which could help to improve feeding efficiency.Moreover,the high sinuosity of leaf mines could decrease the searching efficiency of parasitoids and,then improve the survival rate of leaf mining larva.In conclusion,different leaf mining pests have various feeding behaviors,which had different impacts on leaf morphology,leaf biochemistry and leaf physiology,including nutrient substance,secondary compounds and photosynthesis.Therefore,different leaf mining pests damaged plants at different levels.