QTL Mapping For Important Traits Including Bract And Trichome Of G.herbaceum Subs Africanum

There are only two diploid cotton species of A genome.Gossypium herbaceum?A₁?and Gossypium arboreum?A₂?,both of which are cultivated species.Among them,the Gossypium herbaceum subs africanum(A_1-a),a wild type and has superior fiber compared to G.arboreum?A₂?,which may be an important resource for fiber improvement,and enhance the study of evolution history among the Gossypium species.Therefore,the study of G.herbaceum subs africanum is of great theoretical significance and application value.In this study,the interspecific hybrid materials of G.herbaceum subs africanum and G.arboreum were successfully obtained,and the F_2:3 and F_3:4 population were further obtained.In this study,quantitative trait loci?QTLs?related to the important biological characteristics such as bract angle,petiole trichome and plant architecture were evaluated by adopting the modern genotyping technique of genotyping-by-sequencing?GBS?.The main results are as follows:The developmental stage of annual and perennial of G.herbaceum subs africanum was investigated.It was confirmed that the seedling periods of G.herbaceum subs africanum ranged from 4 to 6 days,the squaring dates ranged from 29 to 30 days after seedling,the flowering time was determined to occur btetween 27 and 31 day after squaring while boll opening dates occurred from 52 to 46 days after flowering.According to the investigation on the angle and shape of bract in G.herbaceum subs africanum,the bracts of G.herbaceum subs africanum gradually spread and flatten after squaring.Moreover,the number and morphology of trichome in different parts of G.herbaceum subs africanum was investigated.The results showed that there was dense creeping short trichome in all parts of G.herbaceum subs africanum and the number of long trichome in the third-leaf petiole was the least.The field morphology of G.herbaceum subs africanum was investigated,and it showed that the first fruit branch node of G.herbaceum subs africanum was 9-10,and the boll shape was near circular.There were lots of thin branches appearing on multiple-years G.herbaceum subs africanum.The F_2:3,F_3:4 and F_2:3 perennial populations of Dianya 10 and A1alz?G.herbaceum subs africanum?were constructed for traits investigation.Except for bract angle and petiole trichome,the rest of the traits fitted genetic characteristics for QTL analysis.The coefficient of variation of each trait in the higher generation was lower than that in the lower generation.In F_2:3 generation,all the plant shape related traits were significantly and positively correlated.In F_3:4 generation,plant height was positively correlated with the first fruit branch node,the first fruit branch node height was positively correlated with the number of fruit branches.Generally,all the traits analysed were significantly and positively correlated.Construction of high-density genetic map based on the F₂ population using GBS method.Genotyping was carried out on parents and 264 individuals,and 9,400 polymorphic markers were obtained.The total genetic distance of the genetic map was 2035.83 cM,with an average markers distance of 0.22 cM.The9400 polymorphic markers spanned across the 13 chromosomes.The largest chromosome among the 13chromosomes was chromosome A04 with a map size of 177.58 cM,while A10 chromosome was the shortest,with a map size of 131.2 cM.The total number of gaps in the genetic map is 56,of which the largest gap numbers located on chromosome A12 with 8 and the least gap numbers located on chromosome A09 with 1.The QTL locimapping4.2 software was applied to analyze the bract angle,petiole trichome,boll length,boll width,boll length/width ratio,plant height,first fruit branch node,first fruit branch node height and fruit branch number.2 QTLs were detected for the bract angle.The three boll-shape related traits,boll length,boll width and boll length-width ratio,5 QTLs were obtained.Moreover,6 QTLs related with petiole trichome were detected.Furthermore,26 QTLs related to plant height,fruit branch number,first fruit branch node and first fruit branch node height were found.