| Cotton is an important economic crop in the world.It is the main raw material of the textile industry and plays an important role in the national economy.Because the cotton has the characteristics of unlimited growth in the appropriate environmental conditions,easy to cause the vegetative growth and reproductive growth is not harmonious,eventually lead to premature senescence in cotton boll abscission,severe yield and quality reduction.Therefore,it is very important to coordinate the relationship between the vegetative growth and reproductive growth of cotton,which is a key factor to achieve high quality,high yield and high efficiency of cotton.DPC technology can shape ideal plant type,rationally regulate the relationship between vegetative growth and reproductive growth,and make cotton breeding level step to a new level.It is more and more extensive by the application of MAGIC population in crop breeding,which makes up for the shortcomings of the narrow genetic basis of conventional breeding,and improves the huge resources for genetic breeding in the future.In order to investigate the sensitivity of cotton MAGIC progeny to DPC,select extreme materials and set up extreme material pool,we will provide materials for further ecological response test.The field experiment was conducted in 2016 and 2017 at the College of Agriculture,Yangtze University in Jingzhou,Hubei Province.It was divided into two steps.The 96 the descendant lines of cotton MAGIC population was used in the first step.DPC was applied at the early flowering stage and the flowering stage,respectively.The objectives of this study were to determine the sensitivity of plant habit,spatial distribution of cotton bolls and yield and yield components to DPC application,the extreme material pool was initially established.The 5 sensitive materials(S1-S5)and 5 insensitive materials(D1-D5)selected from extreme material pool was used in the second step.DPC was applied at the squaring stage,the early flowering stage,the flowering stage and post-topping stage,respectively.The objectives of this study were to determine the sensitivity of cotton growth rate,plant habit,spatial distribution of cotton bolls,yield and yield components,fiber quality to DPC application,in order to estimate the 5 sensitive materials and 5 insensitive materials sensitivity to DPC consistented with the effect of extreme material pool to DPC.The feasibility of the establishment of extreme material pool is demonstrated,which provides ideas for screening the judging of core indicators of the sensitivity of cotton MAGIC progeny to DPC,and provides materials for further ecological response tests.The field experiment results show that:1.Applying DPC could inhibit the vegetative growth of the descendant lines of cotton MAGIC population.The cotton plant height,length of stem node,the number of fruit branches,length of the fifth fruit branch,length of the tenth fruit branch,length of the top fruit branch were reduced after applying DPC in the first year.The agronomic characters of 5 sensitive materials and 5 insensitive materials sensitivity to DPC consistented with the effect of extreme material pool to DPC.The growth rate of plant height was more sensitive to DPC.Growth period was the later,sensitive materials in response to DPC was the larger,and growth period was more front,insensitive materials in response to DPC was the larger,but the growth rate of stem diameter in response to DPC was small.It is suggested that the time of effect of DPC may be related to the material sensitivity to its.2.Applying DPC could inhibit the reproductive growth of the descendant lines of cotton MAGIC population.Spatial and temporal distribution of cotton bolls were affected after applying DPC,and it was bad for bolls setting of fruit branches.The boll number of middle-level,upper-level,inner-level of the descendant lines of cotton MAGIC population were affected,and The boll number of lower-level,upper-level were not affected after applying DPC in the first year.In the second year,the bolls before July 15 were large response to DPC,the bolls from July 16 to Auguest 15 and from Auguest 16 to September 15 were small response to DPC.The temporal distribution of cotton bolls were inhibited after applying DPC,but it could promote the formation of bolls from Auguest 16 to September 15.3.The yield of the descendant lines of cotton MAGIC population were not significant effect by applying DPC.The total boll-nodes,boll number per plant were reduced after applying DPC in two years,but it improved the boll weight.There were no significant effects on cotton seed cotton yield and lint yield,and sometimes it could reduce the lint percentage,this may be related to the factors such as test materials,the different year.It could improve the seed index,and the influence of the lint index to DPC is different from between the different materials,indicating that DPC can regulate the growth and development of cotton seed and fiber.4.Applying DPC couldn't significant affect fiber quality.The micronaire,maturity index of insensitive materials D1 were sensitive to DPC,the maturity index,fiber length,short fiber of insensitive materials D3 were sensitive to DPC,the fiber length of insensitive materials D5 were sensitive to DPC,the fiber quality of other materials were not significant sensitive to DPC.It could affect micronaire which the rank had changed.5.There had a significant differences between the responsiveness of sensitive material S1-S5 and the responsiveness of insensitive material D1-D5 to DPC.The average responsiveness of plant height,length of the fifth fruit branch,number of main stem nodes,the number of fruit branches,length of the tenth fruit branch of 5 sensitive materials to DPC reached significant level compared with 5 insensitive materials.The average responsiveness of length of stem node,length of the top fruit branch of 5 sensitive materials to DPC reached no significant level compared with 5 insensitive materials.But the agronomic traits of sensitive materials response to DPC more sensitive than the insensitive materials.The average responsiveness of yield and yield components of 5 sensitive materials to DPC reached no significant level compared with 5 insensitive materials,and the average responsiveness of the former more higher than the latter.The average responsiveness of fiber quality of 5 sensitive materials to DPC reached no significant level compared with 5 insensitive materials.6.Subject to the cluster analysis based on phenotype responsivity data in the first year,96 descendant lines of cotton MAGIC population were divided into three material pools,including the sensitive material pool(40 materials),intermediate material pool(13 materials)and the insensitive material pool(43 materials).Subject to the cluster analysis based on phenotype responsivity data in the second year,10 descendant lines of cotton MAGIC population were divided into two material pools,including the sensitive material pool(S1?S2?S3?S4?S5)and the insensitive material pool(D1?D2?D3?D4?D5).The results show that the sensitivity of material S1,S2,S3,S4,S5,D1,D2,D3 D5,D4 to DPC consistent with the results established by extreme material pool.In conclusion,this study confirmed that spraying DPC could optimize canopy structure of the descendant lines of cotton MAGIC population,regulate the temporal and spatial distribution of boll and stabilize yield,the sensitivity of 5 sensitive materials(S1-S5)and 5 insensitive materials(D1-D5)to DPC consistent with the results established by extreme material pool.It proved that the establishment of extreme material pool is feasible,responsiveness and sensitivity grade can be used as a screening standard which determine the sensitivity of the descendant lines of cotton MAGIC population to DPC.It also can speed up the selection of cotton high-quality resources.Next,the screening experiment of core index,determined the sensitivity of the descendant lines of cotton MAGIC population to DPC,and ecological response experiment can carry out.This strategy needs to confirmed by more field experiment. |
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