| Lycii Fructus(goji or wolfberry)is the dried ripe fruit of Lycium barbarum L.which is one of the most commonly used medicinal and edible homologous medicinal herbs in China.Lycii Cortex is the dried root bark of L.barbarum and L.chinense Mill.which is one of the traditional medicinal herbs in China.Lycii Folium is the dried fruit of L.ruthenicum Murr.which is used as ethnic medicine in Tibet and Xinjiang regions.Aceria pallida Keifer also known as goji gall mite,is one of the destructive pests of wolfberry.It accompanies the entire wolfberry growing season and is frequently found in main production areas of wolfberry in China.After feeding on tender tissues of wolfberry such as leaves,flower,and fruit stalks,this mite forms a hidden gall and reproduces inside of it which causes abnormal development of flower buds and fruits,resulting in reduction of goji.The closed gall has become a natural protective barrier for the gall mite A.pallida,and conventional pesticides cannot seep into it,making it difficult to control the gall mites.Currently,there is no effective prevention and control method.Preliminary studies have found that there are significant differences in the gall structure and mite population on L.barbarum(LB),L.chinense(LC)and L.ruthenicum(LR).Additionally,strong resistance to the mite has been observed in the field.These differences may provide new ideas or methods for the prevention and control of the gall mite on wolfberry.Therefore,it is necessary to conduct systematic research on the differences and analyze the reasons for the differences.The occurrence of mite population and the response dynamics of three Lycium plants during the process of galling were systematically studied based on the perspectives of gall mites and plants respectively in laboratory.The results are as follows:1.The gall mite A.pallida can feed and reproduce on both LC and LR and induce galls,it also can feed on the cultivated Solanaceae plants(e.g.Solanum melongena L.,Capsicum annum L.and Lycopersicon esculentum Mill.)but cannot reproduce and induce galls on them.2.There are significant differences in the gall structure and mite population of A.pallida among LB,LC and LR.The gall mites only form closed galls on LB,open galls on LC,and mainly unclosed galls on LR(74.4%).The opening length of the galls of LC and LR accounts for about 1/4 of the gall diameter.During the 3～15 days’ infestation,the elongation growth rate of gall epidermal cells on LB was consistently higher than that LC and LR.The fastest increasing rate of mite population was on LB(showing exponential growth since 9 days),followed by LC,and the slowest was on LR.The number of mite eggs,spermatophore density,and mite population on LB were significantly higher than those on LC and LR after 6,9,and 15 days’ infestation,respectively(P<0.05).The gall diameter of LB showed a highly significant positive correlation with the mite population(r=0.848,P<0.01),while the gall diameter of LC showed a significant positive correlation with the population of gall mites(r=0.733,P<0.05),there is no significant correlation between the gall diameter of LR and the mite population(r=0.332,P>0.05).3.Both the total content of cytokinin(CTK)in the gall of LB,LC and LR is higher than that of healthy leaves generally,but the content of indoleacetic-3-acid(IAA)is only higher in the gall of LB than that of healthy leaves.The gall mite A.pallida contains high concentrations of CTK and auxin(AUX).Combined with the transcriptome of genes related to the biological synthesis of CTK and AUX,we hypothesized that these two types of hormones in the gall may be from A.pallida.One kinds of AUX and seven kinds of CTK,isopentenyladenine(IP)for instance,were detected in the gall.The total CTK in galls of LB,LC and LR was significantly higher than that in healthy leaves(P<0.05)at 9 d and 18 d after infestation,and the IAA content was only higher in the gall of LB than that of healthy leaves.Two types of AUX(IAA,indole-3-butyric acid(IB A))and ten types of CTK(IP,etc.)were detected in the body of A.pallida.The total content of these two hormones was significantly higher than that of the gall tissue(P<0.05).The total content of AUX was 2.06,2.12,and 4.57 times higher than that LB,LC,and LR.The total content of CTK was 18.02,10.92,and 63.20 times higher than that of LB,LC,and LR.The transcriptome showed that most of the genes regulating IAA synthesis in galls were significant down-regulation,and most of the genes regulating CTK degradation were significant up-regulation,indicating that plants did not accumulate IAA and CTK during galls formation.It is speculated that the IAA and CTK in the galls maybe originate from A.pallida.4.Nutrient levels in the galls of LB,LC,and LR was LB<LC<LR,defense levels was LB<LC<LR.The mite population ofA.pallida was not significantly correlated with the nutritional levels of the three Lycium plants,but was significantly correlated with defense levels.During gall formation,the gall mite significantly inhibited photosynthesis,but increased sucrose hydrolase activity and promoted mitochondrial respiration,sugar and protein transmembrane transport,sugar and other nutrients synthesis of three Lycium plants.Besides,jasmonic acid(JA)and salicylic acid(SA)synthesis,disease resistance protein expression and phenolics accumulation of plants were enhanced.Compared with the gall of LC,genes regulating the carbohydrates and other nutrient synthesis in gall of LB was significant up-regulation,and genes involved in the key enzymes for JA synthesis(12-oxophytodienoic acid reductase,OPR),disease resistance protein,phenolics and terpenes synthesis as well as abundance of phenolic and terpenes were significantly downregulated/decreased since 9 d’s infestation.Compared with the gall of LR,genes regulating carbohydrates and other nutrient synthesis in gall of LB was significant downregulation,and genes involved in OPR,disease resistant protein,phenolics and terpenes synthesis were significantly down-regulated/decreased since 3 d’s infestation.This paper revealed the differences in gall induction of A.pallida on LB,LC and LR.LB:the weakest defense response,the largest population of mites,the highest IAA content,with a closed gall;LC:stronger defense response,moderate mite population,lower IAA content,with an unclosed gall;LR:the strongest defense response,the minimum mite population,the lowest IAA content,with an unclosed gall.This study provides data supports for further analyzing the gall induction mechanism of A.pallida,and also provides new ideas for the breeding of new anti-mite varieties of L.barbarum,innovating methods for the gall mite prevention and control. |
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