| The high temperature in summer restricted the production of tomato in south China and restricted the annual supply of tomato.Grafting culture with heat-resistant rootstock can improve the heat resistance of tomato,but the production of tomato rootstock is lack of good heat resistance.In this study,20 tomato rootstock germplasm were selected to evaluate the heat resistance of the germplasm according to the heat damage phenotype and growth physiological indexes by heat stress on seeds and seedlings.Cherry tomato and common tomato were grafted on selected heat-resistant rootstocks respectively,and the influence of different rootstocks on the heat-resistance of tomato grafted seedlings was studied,and the physiological response of grafted seedlings to heat stress was discussed,so as to provide reference for the selection and breeding of heat-resistant rootstocks in south China.The main research results are as follows:1.Heat stress inhibited seed germination of tomato rootstock,and seed germination rate decreased significantly with the increase of temperature.At 34℃,the seed germination rate of most germplasms decreased to below 50% except that the seed germination rate of germplasm N3 was 64%.At 37℃,seed germination rate of all germplasm decreased to less than 23%.At 40℃,the seed germination rate of all germplasm was 0.The heat damage index of germplasm G3,N3 and Q2 was 0.12-0.19,showing strong high temperature resistance(HR).The heat damage index of germplasm Q3 and Q5 was 0.39 and 0.40 respectively,showing moderate heat resistance(MR).The heat damage index of germplasm A1,Q4,Q7,C1,C7 and Y4 was 0.51-0.60,showing high temperature resistance(R).2.The heat damage index of tomato rootstock seedlings was positively correlated with plant height and MDA content in leaves,and negatively correlated with SPAD value,stem diameter,fresh weight of whole plant,dry weight of whole plant,and content of free proline in leaves.The heat resistance of the tested germplasm was comprehensively evaluated by the membership function based on the above 7 growth physiological indexes,and the heat resistance of the germplasm G3,N3 and Q2 were ranked 1-3 in order,and the results were consistent with the ranking from small to large of the heat damage index of the seedlings under sub-high temperature stress.It shows that germplasm G3,N3 and Q2 have strong heat resistance,and can be used as backbone germplasm material for the use and breeding of heat resistant tomato rootstock.3.Cherry tomato and common tomato were grafted with high temperature resistant rootstock G3,Q2 and N3,respectively,to study the heat resistance of 6 rootstock combinations.Under high temperature(37℃/28℃)stress for 7 days,the heat damage index of the grafted seedlings was 0.14-0.19,showing strong high temperature resistance(HR).The heat damage index of the rootstock combination FJ/G3 was the lowest(0.14),while the heat damage index of the scion self-rooted seedlings was 0.83 and 0.88,showing high temperature sensitivity(HS).This indicated that rootstock G3,Q2 and N3 significantly improved the heat resistance of scion.4.The effects of high temperature resistant rootstock G3,Q2 and N3 on the growth of tomato seedlings were studied.Under high temperature(37℃/28℃)stress for 7 days,the plant height of grafted seedlings was lower than that of self-rooted seedlings,but the stem diameter and biomass of scion were significantly higher than that of self-rooted seedlings.The stem thickness,fresh weight and dry weight of the whole plant were 35.67%-37.77%,25.23%-32.46% and 16.81%-20.01% higher than that of the self-rooted seedlings,respectively.The stem thickness,fresh weight and dry weight of the whole plant were 35.20%-37.27%,22.37%-30.77% and 15.58%-18.12% higher than that of the self-rooted tomato seedlings,respectively.The root length,surface area and volume of grafted seedlings were significantly higher than that of self-rooted seedlings,and the above three indexes of cherry tomato grafted seedlings were 14.44%-22.67%,25.72%-35.50% and 37.63%-44.21% higher than that of self-rooted seedlings,respectively.The grafted seedlings of ordinary tomatoes were 13.79%-21.43%,24.57%-31.66% and 38.88%-40.67% higher than those of self-rooted seedlings,respectively.The results showed that the aboveground and root growth of grafted seedlings were superior to that of self-rooted seedlings under high temperature stress.5.Under high temperature(37℃/28℃)stress for 7 days,the chlorophyll content,free proline content and SOD,POD and CAT activities in the grafted seedling leaves were significantly higher than those in the grafted seedling,and the above 5 indexes of cherry tomato grafted seedlings were 76.12%-79.16%,69.43%-82.36%,81.70%-92.70%,128.25%-135.87% and 165.56%-202.22% higher than those in the grafted seedling,respectively.The grafted seedlings of ordinary tomatoes were 65.22%-77.15%,76.35%-81.38%,73.55%-81.75%,113.33%-136.67% and 215.00%-236.67% higher than those of self-rooted seedlings,respectively.The MDA content and cell relative conductivity of grafted seedlings were significantly lower than that of self-rooted seedlings.The grafted seedlings of cherry and tomato were 57.64%-59.65% and 41.28%-55.93% lower than that of self-rooted seedlings,respectively.The grafted seedlings of ordinary tomatoes were 47.53%-53.28% and 34.32%-39.35% higher than those of self-rooted seedlings,respectively.Under high temperature stress,chlorophyll synthesis of grafted seedlings was better than that of self-rooted seedlings,photosynthetic ability,cell osmotic regulation ability and protective enzyme activity were improved,cell membrane structure was damaged and the degree of lipid peroxidation of cell membrane was significantly lower than that of self-rooted seedlings,showing strong heat resistance. |
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