Effect Of Water-saving Irrigation On Vegetative Growth,Fruiting Characters And Gene Expression Responsive To Water Stress In Leaf Of ’Huangguan’ Pear Plant

To screen out the optimum water-saving irrigation model for pear plant cultivation in semiarid area in China and provide an experimental basis for clarifying the physiological and molecular mechanisms of pear tree against drought.Five treatments of drip irrigation coded as T1-T5 and flood irrigation as control(CK)had been conducted in a 9-year-old’Huangguan’ pear orchard in Jingtai County,Gansu Province.Some morphological and physiological characters of leaf in growing season,length and diameter of annual branch were measured;and fruit yield per pear plant and traits of fruit quality under different treatments were also tested at harvest.According to the results of our previous RNA-Seq work,the six genes(β-glucosidase,BG;9-cis-epoxycarotenoid dioxygenase,NCED;Auxin response factor 2,ARF2;Auxin response factor 7,ARF7;Ethylene response factor 1,ERF1 and WRKY transcription factor 6,WRKY6)were involved in pear plant responded to water stress;and the relative expression level of the six genes in leaf of pear plant under different water stress were analyzed by the technology of real-time reverse transcription-quantitative polymerase chain reaction(RT-qPCR).The main results were obtained as follows:1.Compared with the CK,T1 processing leaf fresh weight increase,T2 leaf dry weight reduction and water saturation deficit increase,T4 reduce the water saturation deficit;but drip irrigation under mulch treatment(T1～T5)of the leaf area,water loss rate,chlorophyll a and chlorophyll b contents between treatment and control.2.Analysis of mineral elements in the leaves found that p,k,Ca,Fe,b,and Zn content reaches significant levels.Compare with CK,T1,T2,and T3 significantly increased leaf p and k accumulation,T1,T3,T4 and T5 increases the content of Fe in leaf.T2 reduces Ca content in leaves,T2,T3,T4 and T5 for the blades on Zn uptake;each drip treatment had no significant effect on leaf B content.Fruit Mineral Elemental analysis found that different irrigation treatments pear in N,K,Fe,B and Cu were significantly different but P,Ca,Mg,S,Zn and Mn showed no significant difference;compared with the CK,T2 increased the fruit content of Fe,T2,T3 and T4 treated fruits significantly increase the Cu content.3.Year old branches growth assay showed that,compared with conventional irrigation CK,T1,T2,T3 and T4 treatment year old branches length increased significantly,T1,T2 and T4 the deal when the old branches roughness significantly increased;Correlation analysis showed that irrigation and shoot length,thickness showed a significant negative correlation;illustrated in semi-arid areas,many small irrigation "by Drip irrigation" than the views of a few large "traditional irrigation" more conducive pear shoot growth.4.Different Yield measurement results pear plant irrigation shows that when the same irrigation infiltration depth 60 cm,each treatment(T1,T2,T4 and T5)yield per plant with increasing irrigation amount rises;the same amount of irrigation but the irrigation frequency and the depth of infiltration of different T2 compared with T3,T3 significantly increased yield per plant than T2,the difference reached a significant level(α = 0.01,P<0.01).Thus,a few times irrigation,more conducive pear fruit growth and development,and significantly improve fruit yield.Compared with conventional irrigation CK,T3,T4 and T5 and CK yield no significant difference.From the degree of water-saving point of view,treatment T3,T4 and T5 respectively,compared with CK-saving 46.7%,44.3%and 28.1%.The yield increased from consideration,T3 and T5 treatment production increased even more sharply.5.Fruit quality analysis results showed that the differences in fruit quality traits of different treatments reached significant levels.Fuzzy comprehensive evaluation results,processing of fruit quality traits T5 criterion value reached a maximum of 0.93,conventional irrigation criterion value centered,0.45,T3 judge handling the minimum value of only 0.10.Although a small number of irrigation can Increase yield,but irrigation infiltration depth,total lack of irrigation,fruit quality will be greatly minimum.From pear quality and overall performance considering that the process for the T5 Gansu Province Jingtai County appropriate water-saving irrigation mode.6.With increased irrigation,leaves BG and ERF1 relative expression levels show"increased and then decreased after" trend.In addition to T1,the process leaves BG each relative expression level were significantly increased compared with the control;and the relative expression of ERF1 only T4,T5 treatment significantly higher than the control.It showed moderate drought stress may induce varying degrees of expression ERF1 and BG,which can be adjusted to increase the level of ABA and ethylene to further mobilize response pear defense systems to drought.According to pear foliage growth,yield and fruit quality fruit and overall performance were selected for the treatment T5 Gansu Province Jingtai County appropriate water-saving irrigation mode.Under drought stress conditions,pear leaves BG,NCED,ARF2,ARF7,ERF1 and WRKY6 relative gene expression levels,both showed significant differences,indicating that they are involved in the response to drought stress in pear on the expression levels.