Genetic Difference,combining Ability And Heterosis Of Viola×Wittrockiana Inbred Lines

With its gorgeous flowers,long flowering periods,and hardy character,Viola×wittrockiana is important potted and bedding flowers in Viola genera of Violaceae family.Heterosis breeding has been the major approach in Viola×wittrockiana breeding.However,selection and combination of hybrid parents are time-consuming because of blindness.In this study,the genetic differences between nine inbred lines of Viola×wittrockiana and Viola cornuta were analyzed using 14 phonotypes and SRAP and RSAP markers.According to Griffing complete diallel cross,72 crossing were constructed and combining abilities of 14 characters of nine inbred lines were measured,as well as heterosis of ornamental traits and temperature tolerance of these hybrids.The results are as follows.1.The genetic distances and clustering of nine inbred lines were different among analysis by 14 phenotypic traits,RSAP markers and SRAP markers.The smallest genetic distance was observed between S1 and S9 based on phenotypic traits(2.76)or RSAP markers(0.37)respectively.But the smallest genetic distance was found between S1 and S2 based on SRAP markers(0.47).The largest genetic distance was found between S7 and S9(10.18)based on phenotypic traits,and between S6 and S7 based on RSAP markers(0.79),and between S2 and S7 based on SRAP markers(0.75).Based on 14 phenotypic traits,nine inbred lines were classified into two groups,in which of two Viola cornuta inbred lines,S1 and S9,were clustered into one group,and seven Viola×wittrockiana inbred lines clustered into another group.Based on RSAP markers,nine inbred lines were also divided into two groups,one including S1,S9,S2 and S6,the other including S3,S4,S5,S7 and S8.Based on SRAP markers,nine inbred lines could be divided into four groups,one including only S3,another consisting of S7,another S4 and S5,the rests formed another class.2.S7 had the highest GCA in flower diameter(6.11),and S1(2.05)and S9(4.49)had the highest GCA in flower number,but S2 had the lowest GCA(-0.11)in the plant type.S5×S2,S6×S4,S6×S7,S7×S2,S7×S3,S7×S4,S8×S4 are good combination both in flower diameter and the number of flowers.With higher broad sense heritability(73.85%,79.16% and 64.53%)and narrow sense heritability(64.09%?45.82% and 53.28%),flower diameter,flower number and leaf length can be selected on earlier generations,but the other traits with the lower broad sense and narrow sense heritability,should beselected on higher generations.3.The significant negative correlations were observed between the heterosis of F1 generation in the flower number,plant height,leaf and branch number and the phenotypic genetic distances among their parents.So it is not feasible to predict F1 heterosis based on henotypic genetic distances.However,the genetic distances among the parents based on DNA markers(RSAP and SRAP)were positively correlated with the heterosis of F1 generation in plant height and leaf type significantly.And the heterosis of F1 generation in scape length was significantly positively correlated with the genetic distances between their parents based on SRAP.Therefore,some traits heterosis of F1 generation can be predict by genetic distances based on DNA markers.4.After going through at 35? for one week,71 F1 hybrids were divided into four types,namely high heat tolerance,moderate heat tolerance,weak heat tolerance and heat sensitive type based on principal component and cluster analysis of four tolerant indexes(survival rate,tolerant level,electrolyte leakage rate and chlorophyll fluorescence(Fv/Fm)).And 69 hybrids were divided into three types,namely high cold tolerance,moderate cold tolerance and weak cold tolerance,based on their performance of four tolerant indexes after treating with-8? for 10 h.