Study On Yield Heterosis And Heterotic Group Of 14 Heading Chinese Cabbage Inbred Lines

Heading Chinese cabbage(Brassica rapa,2n=20,AA)is an important vegetable originated from China.Hybrid breeding is main breeding method in Chinese cabbage breeding.In order to study the breeding potential of 14 different types of elite Chinese cabbage inbred lines,48 cross combinations(6×8)were obtained by incomplete diallel cross.Field traits were observed for inbred lines and hybrid combinations in 2017 and 2018 to analyze heterosis performance and combining ability performance of yield-related traits.Five methods,include the special combining ability method of yield,the special combining ability method of Yang's simple method,heterotic group specific and general combining ability,the general combining ability of multiple traits and molecular marker.,were used to divide heterotic groups for the tested parent materials to explore suitable method for Chinese cabbage.This study can provide data for the breeding of Chinese cabbage new varieties,and has important theoretical value and practical application value for the utilization of heterosis in Chinese cabbage.The main findings are as follows:1.The general combining ability of 12 traits in 14 inbred line was clarified,which will used as targeted selection of varieties that meet the breeding objectives.13S93,15S964,14S129,14S96,14S473 and 14S496 with good combining ability were selected as parents,which can be widely used in future breeding.2.Griffing and the Yang's simple method were both used to calculate SCA effect value.Comparing the correlation between the twoSCAs and heterosis,it is found that SCA of Yang's simple method has higher correlation with the Mid-parent,High-parent and High-check heterosis,indicating the SCA of Yang's simple method is efficient in breeding practice.3.Heterosis analysis showed that the High-parental heterosis of 45 hybrids gross weights was positive,and the High-check heterosis of 32 hybrids was positive.It indicates that there is obvious heterosis in the test materials.Through two years of field identification,17ce5(13S93×14S420),17ce11(13S664×14S116),17ce30(15S964×15S118),17ce35(14S129×14S116),17ce37(14S129×14S 420)and 17ce38(14S129×15S118)were considered to be excellent combinations with high yield,good quality and disease resistance.It is hopeful that they will be recommended to participate in the regional test.4.By comparing the results of five different methods for heterotic groups,it is considered that the yield special combining ability method(YSCA)is the best method to divide heterotic groups for Chinese cabbage.Using YSCA,14 test pure lines were divided into five groups,such as the first heterotic group includes 13S93 and 14S448,the second heterotic group includes 13S664,11J13 and 15S118,and the third heterotic group includes 09S184,14S96 and 14S443,the fourth heterotic group includes 15S964,14S116,14S420,and 14S473,and the fifth heterotic group includes 14S129 and 14S496.At the same time,test species representing five heterotic groups were proposed: 13S93,13S664,14S96,14S473 and 14S496,which are expected to accelerate the breeding process.