Genetic Regularity Of Fruit Color,Main Pigment Content And Shape Of Tomato Mutant Nor And ’Bell Pepper’ Type Varieties

Tomato（Solanum lycopersicum L.）is an annual herb of tomato genus in the Solanum family.It is a kind of vegetable which is widely cultivated in the world and processed fresh food has a large consumption.The fruit quality of tomato was evaluated from two aspects:nutritional quality and commodity quality.The nutritional quality included lycopene,V_C and soluble solids.Commodity quality includes fruit shape,hardness,size,color and so on,two quality indicators related to tomato sales.In this study,we used the tomato mutant line’nor’（Non-ripening）（P₁）with green ripening fruit as the maternal parent,and the tomato inbred line’yellow pepper’with yellow ripening fruit as the paternal parent（P₂）.A six-generation genetic population was created by hybridization and other methods.The genetic regularity of fruit color,main pigment content and fruit shape was analyzed.The main research results are as follows:1.Genetic analysis of tomato fruit color:（1）The four traits of fruit color,peel color,flesh color and jelly color between green and yellow fruits did not conform to the genetic rule of quality traits,and there was no Mendelian classical separation ratio in F₂,BC₁ or BC₂ offspring.（2）F₂ fruit color separation ratio and flesh color separation ratio are the same,BC₂ also has the same situation,peel color separation type is different from the previous two,confirming that flesh color is easy to affect the fruit color,peel color and jelly color have no close relationship with the fruit color separation.（3）The heredity of shade value is consistent with MX2-ADI-ADI model.The inheritance of fruit color traits between green fruit and yellow fruit was controlled by two pairs of major genes.The additive effect of the major gene was dominant,and the dominant and epistatic effects were weak.The polygenic effect was very weak compared with the dominant gene effect.L value,a value,b value and shade value were33.05%～88.97%,68.99%～92.18%,87.45%～91.78%and 67.26%～90.29%in BC₁,BC₂ and F₂,respectively.The range of multigene heritability was 2.18%-49.52%,1.64%-23.72%,0.49%-8.17%and 1.56%-23.03%,respectively,which indicated that the breeding of green fruit should be started in the early generation.2.Genetic analysis of main pigment contents in tomato fruits:（1）Two pairs of additive-dominant-epistatic major genes+additive-dominant polygenes were the optimal models for chlorophyll content inheritance.In terms of genetic parameters,the heredity of chlorophyll content was dominated by additive effect of the main gene,while there was a certain negative upward effect.The main gene efficiency of F₂ generation was 45.89%,and the polygene heritability was 0,indicating that the chlorophyll content of this combination could be inherited in the progeny stably,but was also affected by the environment.（2）Lycopene content is controlled by two pairs of major genes,mainly additive effect of the major gene,and there is a certain positive epistatic effect,the genetic model is consistent with chlorophyll;The heritability of major gene in F₂ generation was 65.45%,and that of polygene was 0,indicating that lycopene content could be stably inherited in offspring.（3）The genetic model of carotenoid content is different from the previous two pigments in that it has multi-gene epistatic effect,which is MX2-ADI-ADI.The main gene effect was dominant,both additive and dominant effects played an important role,and there was epistatic effect between genes.The heritability of the major gene in F₂ generation was 9.86%（less than 50%）,and the polygene heritability was 0.15%.These results indicated that the inheritance of carotenoid content in tomato was complicated and easy to be affected by environment.3.Genetic analysis of tomato fruit shape:（1）MX2-ADI-AD is the genetic model of fruit transverse diameter and fruit shape index,and the model of fruit longitudinal diameter is MX2-A-AD.The difference between the three shape parameters was that the two pairs of major genes controlling the longitudinal diameter of fruit had only additive effect,but no dominant and epistatic effect.（2）In terms of genetic parameters,two pairs of major genes controlled the genetic rule of fruit shape index of the hybrid combination of oblate（’nor’）and bell pepper type（’yellow pepper’）,with additive effect values of 0.0312.The dominant effect values of the two pairs of major genes were-0.1071 and-0.1041,respectively,which belonged to dominant inheritance.The additive effect of multiple genes[d]was 0.0350,the dominant effect[h]was-0.1265,and the dominant degree（[h]/[d]）was 3.6143,showing positive super dominance.The heritability of major genes was highest in F₂（43.29%）,followed by BC₂（17.65%）and BC₁（9.34%）.Therefore,fruit shape selection was the most efficient in F₂ generation.BC₂ had the highest multigene heritability（58.94%）,followed by F₂（38.02%）and BC₁（0）.The overall result showed a polygene heritability.（3）In the separation generation,the separation ratio of relative traits of fruit surface with and without furrows was:F₂（1:1.32）,BC₁（1:9）and BC₂（6:1）did not conform to the separation ratio expected by Mendel’s classical separation law.During the measurement,it was found that some fruit surface furrows were shallow transitional phenotypes in the population.Therefore,fruit surface furrows were presumed to be quantitative characters.In conclusion,fruit shape of tomato is a quantitative trait,and the selection efficiency of fruit shape is high in F₂ generation.Fruit shape should be selected at an early stage to preserve the target genes for fruit shape,and the influence of environment on fruit shape should be comprehensively considered.