Characterization And Utilization Of An Upland Cotton Germplasm With Semi-Okra Leave And Good Fiber Quality,ZKY-1

Cotton(Gossypium spp.)is an important oil crop and the largest fiber crop in the world.Cotton fiber is the most important natural and renewable resource in the textile industry.In our previous work,an outstanding cotton germplasm with semi-okra leaves and good fiber quality,ZKY-1,was derived from an interspecific hybrid between G.barbadense L.and G.hirsutum L.by using the method of interline crossing and backcrossing.The agronomical character,fiber quality,physiological and biochemical characters,and the whole genome resequencing of the semi-okra leaf cotton germplasm were evaluated in this experiment.In addition,its values in cotton genetic improvement and heterosis utilization was also carried out in this paper,which will provide a theoretical basis in cotton breeding.The main results are as follows:(1)The characteristics of ZKY-1.As the result shown that the yield and yield traits of ZKY-1 were no significant difference compared with its upland cotton background cultivar,CCRI 49.However,its fiber quality was much better than that of CCRI 49,with the fiber length of 34.5 mm,fiber strength of 38.4 cN·tex-1 and Micronaire of 4.6.Besides,the plant height,first fruit node,numbers of fruiting branches,boll weight,germination rate,and germination potential were better than that of CCRI 49.There was no significant difference between the ZKY-1 and the CCRI 49 in the net photosynthetic rate at the square stage and boll period,although ZKY-1 was significantly lower than that of CCRI 49 at the flowering stage.For the total content of chlorophyll,no significant difference between the ZKY-1 and CCRI 49 was detected at the square and flowering stage,but at the boll stage in which the total content of chlorophyll of ZKY-1 was significantly higher than that of CCRI 49.In addition,the activity of SOD and POD in ZKY-1 were significantly higher than that in CCRI 49 at the square stage and the flowering stage,while no significant difference was found for the content of MDA.At the boll period,the activity of POD in ZKY-1 was significantly lower than that of CCRI 49,and the MDA content was significantly higher than that in CCRI 49,while no significant difference was found for SOD activity.(2)The inheritance of the semi-okra leaf characteristics of ZKY-1.The leaf lobe index of ZKY-1 obtained in this study was 0.75±0.01,indicating the leaf type was semi-okra leaf.The plants in the population showed consistent performance,indicating the stable genetic characteristics,and its semi-okra leaf was different from that already found in upland cotton.The leaf type of the Fi hybrid between ZKY-I and normal leaf-type of upland cotton was intermediate form and the character segregation happens among F2,in accordance with the rule of the segregation ratio controlled by a dominant gene by Chi Square test.(3)The heritability for the fiber quality of ZKY-1.The hybrids obtained by crossing ZKY-1 with different upland cotton germplasm shown a relatively strong mid-parent heterosis in fiber quality traits such as the fiber length and fiber strength,and some combinations shown significant over parental heterosis,which indicated its value in the utilization of cotton heterosis.(4)The whole genome were compared with the upland cotton reference genome,TM-1,and the sea island cotton reference genome,3-79 in this study.Compared with upland cotton sequence,there were 1650006 SNPs,12898 genes with non-synonymous,290072 small InDels,and 1452 genes with insertion and deletion.Compared with sea-island cotton sequence,there were 9782027 SNPs,9180 genes with non-synonymous,1918795 small InDels,and 3111 genes with insertion and deletion.(5)There were significant differences in the pathway related genes between ZKY-1 and the reference genomes in terms of fatty acid metabolism,phenylalanine metabolism,oxidative phosphorylation,plant hormone signal transduction,starch and sucrose metabolism,Ribosome pathway etc.,which might be the functional genes that control cotton fiber quality and leaf shape.Overall,ZKY-1 with stable inheritance semi-okra and excellent fiber quality was an outstanding upland cotton germplasm developed from a natural interspecific hybrid plant,it could be used as an excellent germplasm resource for cotton improvement in fiber quality,plant type and leaf type,as well as the utilization in cotton heterosis.