Evaluation Of Nitrogen Utilization In The Solanum Pennellii Introgression Lines And Preliminary Study On Mechanism Of High-efficiency Line

Nitrogen is one of the major elements necessary for plant growth.At present,the excessive application of nitrogen fertilizer and low nitrogen utilization rate in vegetable production in China have become an important factor limiting the sustainable development of vegetables.Screening and culturing tomato with high-efficiency nitrogen germplasm is one of the most effective ways to reduce nitrogen fertilizer application and increase the nitrogen utilization rate.S.pennellii is a wild tomato species with high resistance to biotic stress and abiotic stress.In this study,we set two nutrient solutions for 50 introgression lines materials,high-nitrogen(5 mmol·L^-1,High-N)and low-nitrogen(0.3 mmol·L^-1,Low-N).We try to evluate the mechanism of nitrogen absorption and utilization and positioned nitrogen-high efficiency lines initially,and then explore the efficient mechanism of nitrogen absorption and utilization of nitrogen high-efficient lines.The main results are as follows:1.50 lines of S.pennellii introgression line and its female parent Solanum lycopersicum M82 were cultured under normal and low nitrogen conditions.22 nitrogen-related indicators were investigated for each line.We analysis the coefficient of variation and principal component of the indicators and the final selection criteria for the nitrogen efficiency of S.pennellii introgression lines were determined:root dry weight under Low-N conditions and relative shoot dry weight were the main screening indicators,shoot dry weight under Low-N condition and the nitrogen utilization of relative shoot were the reference indicators.According to the screening criteria,we think IL2-3 was the nitrogen high-efficient line.2.For study the effects of low nitrogen on plants growth,nitrogen high-efficiency line IL2-3 and its female parent M82 screened were treatment with high nitrogen and low nitrogen.The results showed that nitrogen high-efficient line IL2-3 comparing with female parent M82,morphological indexes including the total root length,root volume,root surface area,root vitality,oldest leaf SPAD value and oldest/youngest leaf SPAD value were significantly higher;Imax value was higher,and Km value,Cmin value were lower in IL2-3 under low nitrogen stress.The fluorescence parameters including leaf minimal fluorescence yields?F₀?,variable fluorescence yields?Fv?,photochemical quenching?qP?and so on were significantly reduce under low nitrogen stress,and IL2-3 had a lower decrease than the M82.The nitrate reductase activity?NRA?and glutamine synthetase activity?GSA?in leaves were significantly higher than the roots in IL2-3 and M82,and IL2-3 was significantly higher than M82 under low nitrogen stress.The above results shows,IL2-3 had a developed root system,the stronger ability and rate of N,and stronger adaptability under low nitrogen;the photosynthesis time was longer in the oldest leaf and more photosynthetic materials were produced;absorption ability of luminous energy was increase by keeping a higher photochemical quenching,therefore there is more luminous energy for photosynthesis;the ability of reduce NO₃^-and assimilate NH₄⁺were higher in leaves and roots.3.The genes related to nitrogen absorption metabolism located Chromosome 2 were searched by NCBI in S.pennellii and Solanum lycopersicum M82,specific genes of Chromosome 2 in S.pennellii were analysis using qRT-PCR?supplement table 1 and 2?.Three genes of mitogen-activated protein kinase 7?MAPK7?,amino acid transporters ANTL1-like?ANTL-1?,serine/threonine protein kinase STY17-like?STY17?were selected in the experment.After low-nitrogen treatment,the relative expression of MAPK7 and ANTL1 in the leaves and roots of the IL2-3 of the nitrogen high-efficient line were induced and increase significantly,and STY17 was significantly increased in the leaves.The reason may be that the MAPK7 and ANTL1 play an positive role in the process of nitrogen absorption metabolism in the nitrogen high-efficient line IL2-3 under low nitrogen stress,while STY17 plays a role in the process of nitrogen metabolism.