Physiology And Metabolome Response Of Different Potato Varieties To Alkaline Salt Stress

In recent years,the increase of land salinization area has become a major problem globally,which seriously threatens the ecological environment and food security.Land salinization affects the normal growth and development of crops,and seriously restricts the development and capacity improvement of agricultural production.As the fourth most important grain and vegetable combination crop in the world,potato has become a wide planting range in China.Some scholars believe that the harm of alkaline salt stress to crops is more significant and complex.At present,there are many studies on saline-alkali stress to potatoes,such as Na Cl and mixed salt stress,while few studies on alkaline salt stress in potatoes,so it is important to study the response mechanism of alkaline salt stress in potatoes.Six main potato varieties including’Holland 15’,’Xingjia 2’,’Hou Qihong’,’Kang Nibeike’,’Kexin 1’and’V₇’were selected as materials,which were planted in the flowerpots for 7 days.And then,seedlings with consistent growth were selected for stress with Na HCO₃salt solution（0,10,20,30,40,50 mmol/L）at different concentrations,and the changes of physiological indicators such as biomass,photosynthetic characteristics,root activity,soluble protein content,osmotic regulatory substances,and antioxidant enzyme activity of different cultivars were studied.Combined with the metabolomics technology,the different metabolite change rules and key metabolic pathways of relatively strong and poor salt-tolerant varieties were analyzed,so as to deeply reveal the physiological mechanism of potatoes response to alkaline salt stress,and provide theoretical basis for germplasm resources innovation,variety breeding and salt-tolerant cultivation of potatoes.The main results are as follows:（1）Alkaline salt stress significantly affected the growth of potato seedlings.After processing with alkaline salts at different concentrations,the growth of six varieties of potato seedlings was inhibited to different degrees.The results showed that high concentration stress inhibited the growth of potato seedlings more than medium and low stress treatments.After processing with 50 mmol/L alkaline salt,the plant height,root length,stem thick,root crown ratio and leaf area of six varieties were significantly lower than the controls.Combining the indexes,the overall conditions of’V₇’were better than other varieties,while’Kang Nibeike’is worse than others.（2）The stress significantly affected photosynthetic properties of potatoes by alkaline salt.Chlorophyll content,nitrogen content and leaf temperature of six potato varieties varied greatly.As the increase of stress concentration,those of’V₇’and’Xingjia 2’increased,showing strong salt-alkali tolerance,while low and medium stress concentration promoted the photosynthesis indexes of’Hou Qihong’,’Holland 15’and’Kang Nibeike’,while high concentration has the significant inhibition.（3）Alkaline salt stress significantly affected the root vitality,soluble protein content and antioxidant enzyme system.Under the alkaline salt stress,root vitality and soluble protein content of six potato varieties increased with the stress,and the content of proline and malondialdehyde gradually increased.（4）Alkaline salt stress significantly affected the activity of antioxidant enzymes in potato seedlings.The overall activities of SOD,POD and CAT showed a trend of increasing first and then decreasing with the increase of stress concentration.POD and CAT had synergistic effects in scavenging reactive oxygen radicals and improving the antioxidant capacity of cells.（5）Correlation analysis showed that the alkaline salt stress concentration was very positively correlated with leaf temperature,proline,malondialdehyde,and negatively with root viability and POD activity,and with plant height,stem size,root length,leaf area,soluble protein,and CAT activity.（6）The principal-component analysis of the related growth and physiological indicators showed that the alkaline salt resistance ability of six potato varieties ranged from strong to weak in order:V₇>Kexin 1>Xingjia 2>Holland 15>Houqihong>Kang Nibeike.（7）Through UPLC-MS platform detection and KEGG analysis,a total of 356different metabolites were detected from Kang Nibeike and V7,including 43 amino acids and their derivatives,46 sugars and alcohols,55 organic acids,106 phenolic acids,15 fatty acids,26 nucleotides and their derivatives,19 alkaloids,3 vitamins,5 steroids and glycosides,1 terpenoids and 37 other metabolites.Of these,221 differential metabolites were up-regulated and 135 metabolites were down-regulated.The number of differential metabolites between the 16 comparison groups was higher than the number of those down-regulated,and the number of differential metabolites in the roots of’V₇’was higher than that in the roots of’Kang Nibeike’.（8）Potato can improve stress resistance by adjusting different metabolites such as sugars and alcohols,organic acids,phenolic acids and fatty acids.A total of 356 differential metabolites were detected from the two varieties,which participated in 100 differential metabolic pathways.Through the comparison of different stress treatments,they were enriched in 8 significantly different metabolic pathways,including pyrimidine metabolism,fatty acid biosynthesis,secondary metabolite biosynthesis,keratin,suberin and wax biosynthesis,which participated in and regulated the biological process of potatoes response to alkaline salt stress,and were closely related to the ability of potato to resist alkaline salt.In contrast to’Kang Nibeike’,’V₇’can improve its resistance to alkaline salt stress through active TCA cycle,fatty acid metabolism and phenolic acid metabolism.