Mechanism Of Potato In Response To Continuous Cropping Stress In Yellow River Irrigation Farming Districts Of Gansu

Follow the rice, wheat and maize, potato (Solanum tuberosum L.) is the fourth-mostimportant food crop worldwide. It is one of the major crops in China as well. To date, theplanting acreage and production of potato in China ranked as top one worldwide. However,the shortage of the irrigation water and the continuous cropping significantly impacted theyield, quality, commercialization rate and the storage life of the potato tuber in China. Thecontinuous cropping currently is the main factor that affect the potato production in thepotato growing. In this study, the morphological, physiological characteristics and the tuberquality under the continuous cropping were analyzed. The genotypes that showed resistanceagainst the continuous cropping were characterized. The composition and characteristics ofthe root secretion were analyzed. The impact of phenolic acids on the growth of potato wasdiscussed. The effects of Ca signaling on the resistanse of potato to the continuous croppingwere also analyzed. The effects of organic fertilizer and biological fertilizer on easingcontinuous cropping stress were evaluated. The outcomes of this study should provide thetheoretical foundation for the sustainable development of the potato production as well asthe farming land ecological system in arid land of Northwest Continuous Cropping Region.The main conclusions were summarized as follow:1、In the field of6years continuous cropping, the plant height of8varieties wassignificantly lower than those from non-continuous cropping field. The maximumdifference was observed during the seeding stage, while the minimum difference showedduring the squaring stage. The continuous cropping affected the longitudinal developmentof the tuber. Among8varieties, the plant height of Atlantic is the least affected, the averagedecrease of the height during the4growth stage is21.22%. Favorita is the most affected(44.45%). All tested varieties showed significant yield reduction in the6year continuouscropping field, the reduction is ranged from78.14%(Qingshu-9)-to97.84%(Favorita). Thecommercialization rate of Qiangshu-9is extremely low, suggesting that the harvested tuberdid not have any economic value. The commercialization rate usually is one of theimportant evaluation indexes when the yield is fixed. Therefore, the results indicated thatAtlantic is relatively resistant to the continuous cropping, six years continuous croppingseverely reduced the yield of potato, the harvest index of unit area was significantly declined. As conclusion, the6years continuous cropping land is not suitable for growingpotato.2、In the5years continuous cropping field, the plant height of5varieties wasgradually reduced with the development of the plant. The plant height of shepody andKexin-1was decreased33.17%and31.69%, respectively. The root length, root surface areaand root volume showed slightly reduction when compared with those from the controlfield. The physiological data combined with the commercialization rate index indicated thatKexin-1is sensitive to the continuous cropping.3、When compared to the rotation field, one or two years continuous cropping did notaffect the yield of potato. After3years continuous cropping, the yield reduced to44-56%.The results suggested that Atlantic should not be continuous cropped more than2years.The photosynthetic activities of potato plant was significantly affected by the continuouscropping. Pn、Gsand Trwere declined with the increasing of continuous years, Ciwasincreased. F0of chlorophyll fluorescence were declined with the increasing of continuousyears，Fv/Fm、ΦPSIIand qP were increased. SOD, POD and CAT of leaves showed increasingat early years and decreased with the increasing of continuous years. When compared withthe non-continuous cropping, the MDA content of leave did not affected by1or2yearscontinuous cropping, but increased4-6folds when continuous cropping last3-5years. Theroot activities, total absorption surface and active absorption area were significantlyreduced with the increasing of continuous year. The results thus suggested that the potatocontinuous cropping obstacle was caused by the variation of photosynthetic and antioxidantsystems, the change of the morphological characteristics of the plant, the reduction of rootphysiological activities and absorption area. as a results, the absorption ability of root touptake nutrient and water from the root-soil interface was reduced, and therefore the growthof tuber and dry matter accumulation in tuber were also affected. The yield formation oftuber and the normal growth of above ground part of plant were further affected, and thepotato continuous cropping obstacle was formed as a result.4、The soil solutions from3year continuous cropping field and rotation field duringthe seedling and the falling flower stage were against the GC-MS analysis, a total of40organic chemicals were analyzed for both continuous cropping and rotation. During theseedling stage, about14organic chemicals were detected in the soil of the continuous cropping field: Pelargonic C9H20, N, n-dimethyl formamide,2-octenal, octenal, undecane,Acetic acid-ethyl-Hexyl ester,2-11allyl aldehyde,1-dodecene,1–13OL,1-15-Ene, dibutylhydroxy toluene,1,2-acid22-methylpropyl ester,5-18Ene. During falling flower stage, allorganic chemcials except N, n-dimethyl formamide were detected in both continuouscropping and rotation field soil solution, suggesting that N, n-dimethyl formamide is theautointoxication of allelopathic substance, but the inhibition activities of N, n-dimethylformamide need to be studied in the future. About10more chemicals were detected duringthe falling flower stage, Formamide-n, N-dimethyl, aldehyde, Are octan-ethyl, cetene,8-17Ene,16acid propyl ester, eicosane, octane,3-3Dimethyl. hexadecanoic acid also calledpalmitinic acid, it is a known autointoxication substance. The roles of hexadecanoic acidand other nine chemicals in affecting potato growth need to be studied in the future.5、Para-hydroxybenzoic acid, vanillic acid and ferulic acid are three importantautointoxication of allelopathic substances. Application of these three solution and mixtureon the potato plant showed inhibition effects on plant height, stem diameter, above groundstem numbers, creeping stem numbers and root length. The mixture that include all threechemical showed greater effects than individual application. The root activity andchloroplast content of potato also affected by the chemicals, the net photosynthetic rate wasdeclined as a result. The inhibition activities were enhanced with the increasedconcentration of solution. Those effects might directly involved in the development ofpotato plants. With the addition of phenol acid, especially the mixture of three chemicals,the MDA content of leaves were increased and the activities of antioxidant enzymes weredecreased.6、The direct spraying of CaCl2on the leaves can significantly ease the inhibitionactivities of the continuous cropping on the potato seedlings. The starch content, vitamin C,soluable protein content, hardness of tuber, and tubers per plant were also increased whenCaCl2was sprayed. The continuous cropping caused the reduction on chloroplast content,while proline and soluble sugar content were significantly restored. The SOD and CATactivities were increased, the MDA content and the active oxygen were declined. Theresults indicated that the spraying of CaCl2could significantly increase the continuouscropping resistance of potato plant, ease the physiological obstacle caused by continuouscropping, benefit the growth of the potato plant, as a result improve the nutrient and yield of tubers.7、Addition of mixture fertilizer includes organic fertilizer, ammonium humic acid,compound fertilizer and microbal fertilizer showed significant effects on the yield and theeconomical value of tuber. The optimized mixture of organic fertilizer, ammonium humicacid compound fertilizer and microbal fertilizer is800kg/667m2、75kg/667m2、5kg/667m2,respectively.