Breeding Of Sterile Lines And Heterosis Utilization For Mustard Hau CMS

Mustard（Brassica juncea L.）is an important vegetable crop of the Brassica family in China.At present,the main types of cytoplasmic male sterility applied in mustard are hau CMS,ogu CMS,zhacai（Brassica juncea var.tumida Tsen&S.H.Lee）CMS and Moricandia arueusis CMS.The study of the functional mechanisms and breeding utilization of different CMS genes has important theoretical and practical implications for the utilization of mustard heterosis.Since the discovery of mustard hau CMS,the functional mechanisms of the sterility genes and the utilization of heterosis have been important issues for mustard breeders.In this study,the genetic expression vector was constructed to investigate whether orf288 is a sterility gene for hau CMS in mustard.The cytoplasmic male sterile lines 22-02A（sterile source of hau CMS）and 22-03A（sterile source of ogu CMS）were used as the main material to analyse the heterosis and fitness of the two cytoplasmic male sterile lines in tiller mustard.At the same time,the dominant cross combinations of tiller mustard were screened and applied to the selection of mustard hybrid generation varieties and large-scale production.The main results of this study are as follows:1.Functional validation of mustard hau CMS sterility genes.In this study,fo-ur expression vectors,Ca MV35S:mts:orf288:GFP,Ca MV35S:mts:orf288,LAT52:mts:orf288:GFP and LAT52:mts:orf288,were constructed for Agrobacterium-mediated g-enetic transformation of mustard in 20P-16B,and all T₀generation transgenic posi-tive plants showed normal floral organ architecture with viable pollen.q RT-PCR a-nalysis of flower buds from some of the transgenic positive plants revealed that t-he expression of orf288 in flower buds of the transgenic positive plants was upre-gulated by more than 300-fold compared to that in flower buds of 20P-16B mater-ial,but still had a large difference compared to the expression of orf288 in flower buds of the purple tiller mustard hau CMS sterile line（20P-16A）.Further obser-vations on the floral organ phenotypes of transgenic positive plants from T₁and T₂generations will follow.2.Analysis of mustard heterosis.Fourteen hybrid combinations were formulated using the homozygous cork mustard cytoplasmic male sterile lines 22-02A（hau CMS）and 22-03A（ogu CMS）as the parent and seven cork mustard self-cross lines as the parents.In terms of average overage advantage,the hybrid combination with 22-02A as the parent had a stronger overage advantage in plant width,rosette leaves and number of tillers than the hybrid combination with 22-03A as the parent;the hybrid combination with 22-03A as the parent had a stronger overage advantage in plant height,leaf length,petiole length and individual plant weight than the hybrid combination with 22-02A as the parent.In addition,a comprehensive analysis of the heterosis of tiller mustard yield traits（number of tillers and weight per plant）resulted in the screening of four hybrid combinations with significant superlative advantage:22-02A×22-05,22-02A×22-09,22-03A×22-05 and 22-03A×22-08.3.Analysis of the cooperativity of cytoplasmic male sterile lines in mustard.In terms of general cooperativity（GCA）effects for each agronomic trait,22-02A showed higher GCA levels in plant width,rosette leaf number and tiller number,while 22-03A showed higher GCA levels in plant height,leaf length,leaf width,petiole length,petiole width and single plant weight.The sterile lines 22-02A and the parental selfing lines 22-04,22-05,22-06 and 22-09 showed higher levels of SCA in single plant weight,while the sterile lines 22-03A and the parental selfing lines 22-07,22-08 and 22-10,showed higher levels of SCA in single plant weight.The above indicates that the sterile cytoplasm of both hau CMS and ogu CMS has greater application in the utilization of tiller mustard hybrid advantage,and the utilization of both in the breeding of tiller mustard hybrid advantage should be enhanced subsequently.