Gene Mapping Of Bptd Mutant And QTL Analysis Of Spike-related Traits In Barley

Barley is widely grown in the world,and its annual output is second only to rice,wheat and corn.Therefore,it is important to cultivate high-yield barley varieties.Panicle traits play an important role in yield structure.In the early stage,we identified a mutant with abnormal spikes,was named bptd（barley panicle tip degradation）.In this study,the agronomic traits of the mutant was identified;DAB staining,paraffin section preparation and physiological and biochemical indexes of the young panicles were analyzed;The genetic analysis of the mutant bptd was carried out and the mutant gene was located by Super-BSA method.In addition,the correlation and QTL analysis of important agronomic traits（plant height,panicle length,awn length,flag leaf width,flag leaf length）in barley RIL population in recent four years were conduted.The results laid a foundation for further exploring the mechanism of the formation of barley panicle tip degeneration and the cloning of related genes and improving barley yield.The main results were as follows:（1）The results showed that the panicle tip development of the mutant bptd was abnormal,showing as"half white panicle".Compared with the wild type,the plant of bptd was dwarf,the panicle length was shorter,the grain number of per panicle was decreased,the weight of one hundred-grains was decreased,and the length of all internodes was significantly shortened.（2）By DAB staining of young panicles,it was found that there was accumulation of H₂O₂ at the tip of the young panicle of mutant bptd.At the same time,paraffin section observation was carried out on the young panicle of mutant bptd and wild type at the same developmental stage.The panicle width,panicle axis width and panicle primordium width were measured.It was found that the cells at the tip of the young panicle were larger,but the numbers were reduced,the arrangements were loose and disorderly,the cell walls were thicker.It indicated that the meristem at the tip of young panicles was damaged.（3）The MDA content,SOD activity,POD activity,CAT activity and GSH content of mutant bptd young panicle at four developmental stages were measured.The results showed that the membrane system of mutant bptd young panicles was damaged,and the antioxidant system might be damaged,and the antioxidant capacity decreased.（4）The genetic analysis of the mutant bptd indicated that the mutation was controlled by a single recessive nuclear gene.Super BSA method was used to locate the mutant gene.Mixed pools of degraded plants at the top of panicle in F₂ population and wild type ZJU3 were sequenced simultaneously.The gene was mapped in the210,097,814-309,786,035 region of chromosome 6H.There were 1269 candidate genes in this region,including 12 non-synonymous mutant genes.（5）There were significant differences in plant height（PH）,panicle length（PL）,awn length（AL）,flag leaf width（FLW）and flag leaf length（FLL）between parents GP and H602 of RIL population.The measured data of RIL population in recent four years were analyzed.The results showed that the five agronomic traits accorded with normal distribution.PL was very significant or significant positively correlated with PH,AL,FLW and FLL in the past four years.There was also a very significant positive correlation between FLL and FLW in the last four years.（6）The recent four years’datas of five agronomic traits in RIL population were analyzed by using the software of IciMapping.A total of 37 QTLs were detected.It was found that the same locus could be detected for three consecutive years in the QTLs controlling PL on 2H and AL on 5H in barley,which were stable inheritance.One major QTL was detected at 3H,which was located between marker1494192-Marker 2152945,and was related to four traits of PH,AL,FLW and FLL.The QTL between marker 5648355-Marker 5163262 at 5H controlled both PL and AL traits.The QTL between marker 4994432-Marker 4971228 at 5H controlled the expression of both PH and FLL traits.This fully reflects the existence of multiple effects.