| Potato has the advantages of strong adaptability,high yield and comprehensive nutrition.Compared with other vegetable crops,potato also has the advantages of high starch content as a kind of grain and vegetable crops.At present,the application of starch has been transferred from the original food to industrial production and life in all aspects.In this study,5 different genotypes of potato were used as materials.The potatoes harvested at 90 d and 120 d,respectively,were mainly explored for differences in yield,dry matter content,total starch content,starch particle-size distribution,amylose content and activities of enzymes such as adenosine diphosphate glucose pyrophosphorylase(AGPase),soluble starch synthase(SSS),granular coagulated starch synthase(GBSS)and starch branching enzyme(SBE)between the two different growth stages.The correlation and difference of these indexes were analyzed to explore the formation mechanism of difference for starch content in different genotypes of potato,which in doing so provide reference for the breeding of potato varieties with high starch content.The main results are as follows:I.In the two different growth stages,the yield per plant,dry matter content,total starch content,amylose content and starch extraction amount were higher at 120 d fordifferent potato materials,and the same potato material showed overall differences in the two different growth stages.The results indicate that 90～120 d is an important period for accumulation of dry matter and starch in potato tubers.In the two different periods,material A1 had the highest dry matter content and total starch content,which could provide parents for breeding of potato varieties with high starch content.II.Activities of key enzymes for starch synthesis were determined in the two different growth stages,and the results showed that the activities of enzymes AGPase,SSS and GBSS decreased at 120 d of growth stage.Combined with the results of previous studies in other crops,it was suggested that the decreased activities of these enzymes might be related to the physiological maturity stage of potato.However,different from the three amylases mentioned above,the activity of enzyme SBE increased slightl y at 120 d of growth stage.III.The correlation analysis showed that potato starch synthesis was regulated by amylase.Among them,the activity of enzyme GBSS showed a significant positive correlation with amylose content in different potato materials,which indicated that GBSS enzyme was mainly involved in amylose synthesis.There was no significant correlation between AGPase activity and total starch content and amylose content,suggesting that enzyme AGPase may play a role in starch synthesis and termination,not directly involved in the starch accumulation process.Enzymes SSS and SBE jointly regulate amylopectin synthesis and total starch content.IV.Potato starch particle size is closely related to potato processing and other industrial applications.By extracting starch from different potato materials at different growth stages,the microstructure and particle-size distribution of starch particles were studied.The results showed that the micromorphology of starch grains of five different potato materials showed three kinds of morphology: long ellipse,ellipse and oval.Majority of large starch grains were oval,medium starch grains were oval and small starch grains were oval.In terms of particle-size distribution,the particle sizes of A1,A2,T1,T2 and T3 materials at 90 d of growth period is in the range of 2.29-43.65 um,1.73-48.32 um,1.86-58.90 um,3.94-49.41 um,8.26-53.39 um,respectively.At 120 d of growth stage,their particle-size distribution ranged from 3.95-52.53 um,4.82-54.11 um,2.44-52.13 um,3.24-63.29 um,5.90-47.49 um,respectively.The results showed that the starch particle-size distributions of different potato materials were different,and the changes of starch particle size of different potato materials werealso different in the two different growth stages. |
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