Genetic Analysis Of Awn Length And Branch Number And Transcriptome Analysis Of Light Response Of Rhizome In Oryza Longistaminata

Oryza longistaminata（O.longistaminata）has many excellent characteristics,such as perennial and resistance to insect,bacterial blight,black streaked dwarf disease,drought and so on.The AA genome of O.longistaminata,which is the same as that of the Asian cultivated rice,can reduce the reproductive barrier between O.longistaminata and the cultivated rice,and make the cultivated rice obtain excellent characters from O.longistaminata.In this study,we used a japonica cultivated rice Balilla which is no awn and less branches as the female parent crossed with the male parent O.longistaminata which has a long awn and more branches.Followed by embryo rescue,we got the F₁ and the F₂population by F₁ selfing.By the molecular linkage map constructed by the PCR based In Del（Insertion-Deletion）markers,we mapped the QTLs（Quantitative Trait Loci）controlling the awn length and branch number of rice.The main results of this study are as follows:1.The awn length of O.longistaminata was 5.68±0.27 cm,but Balilla had no awn.The awn length of F₁ hybrids was 7.86±0.30cm,which was larger than that of male and female parents.Eleven QTLs（q AL-2-1、q AL-2-2、q AL-3-1、q AL-4-1、q AL-4-2、q AL-5-1、q AL-7-1、q AL-7-2、q AL-8-1、q AL-10-1 and q AL-11-1）,which control the awn length of rice,were obtained by software QTL Ici Mapping 4.0 in 2017 and 2018.These QTL can explain 2.7%-28.0%of phenotypic variation.Most of the alleles were from the O.longistaminata,but five QTLs（q AL-2-1、q AL-2-2、q AL-3-1、q AL-7-1and q AL-7-2）were also from the awn-free parent Balilla.q AL-4-1 and q AL-5-1 were detected in both years.The allele contributing most for the awn length is q AL-4-1 on chromosome 4,which contains an An-1 gene regulating awn elongation.q AL-7-1 and q AL-7-2detected in 2017 have not been reported.2.The number of primary branches of the male parent O.longistaminata was 13.70±1.25,while that of the female parent Balilla was 8.90±1.45,and that of the hybrid F₁ was 17.50±3.12,which was more than both parents.The branch numbers in F₂ population tended to the normal distribution,which indicated that the branch number was a quantitative character and can be used for QTL analysis.QTL mapping was carried out for the branches number in F₂population of in 2016 and 2017.The results showed that six QTLs（q NPB-2-1、q NPB-4-1、q NPB-8-1、q NPB-9-1、q NPB-10-1 and q NPB-10-2）controlling the primary branch number were detected on chromosome 3,4,7 and 9 respectively.q NPB-4-1 had the biggest effect among all detected QTLs,and it was detected in both years.In 2016,q NPB-4-1 could explain 17.21%of the phenotypic variation;in 2017,q NPB-4-1 could explain 5.75%of the phenotypic variation.In this experiment,most of the alleles increasing the number of primary branches were from the male parent,O.longistaminata,while the q NPB-4-1allele controlling the number of primary branches on chromosome 4 was from the female parent Balilla.3.A total of seven QTLs（q NSB-1-1、q NSB-3-1、q NSB-3-2、q NSB-4-1、q NSB-7-1、q NSB-7-2 and q NSB-8-1）controlling the secondary branch number were detected,which were located on chromosome 1,3,4,7 and 8 respectively,in these two years.Among them,q NSB-4-1 has the biggest effect value and has been detected in QTL mapping in both years;q NSB-4-1 can explain 14.50%of phenotypic variation in 2016,and can explain 12.73%of phenotypic variation in2017.q NSB-7-2 locus was also detected in both years;q NSB-7-2 could explain7.63%of phenotypic variation in 2016,and could explain 5.65%of phenotypic variation in 2017.In this experiment,the alleles of q NSB-4-1,q NSB-7-1 and q NSB-7-2 controlling the secondary branch number were mostly from Balilla,while the alleles of q NSB-1-1,q NSB-3-1,q NSB-3-2 and q NSB-8-1 were from O.longistaminata.4、Light has a great influence on the growth and development of plants,but there are few reports about the light influence on the growth and development of rhizome and its molecular mechanism.In this study,O.longistaminata plants were cultured with or without shading,and we compared the transcriptome of the shortened nodes of rhizome under the two conditions,to explore the signal pathway of light regulating the development of rhizome.The main results of this study are as follows:In the non-shading treatment group,the internode length of the rhizome which was going to come up out of the mud was significantly shortened;In the shading treatment group,the internode length of the rhizome out of the mud was not significantly shortened,which was remarkably different from that of the rhizome under the condition of the non-shading.The results showed that light could inhibit the internode elongation of rhizome.The high-throughput RNA sequencing technology was used to sequence the transcriptomes of the rhizome out of the mud under shading and non-shading conditions.By the transcriptome analysis,2174 differentially expressed genes were obtained.Compared with the control group,1053 genes were up-regulated and 1121 genes were down-regulated.Gene Ontology（GO）functional annotation and enrichment analysis of the differentially expressed genes showed that these genes were divided into 54 types of functions,mainly including cell composition,metabolic process,catalysis,transport activities,and so on.The KEGG pathway functional analysis showed that these genes involved in 277 metabolic pathways,most of which involved in carbohydrate metabolism,signal transduction and lipid metabolism.In addition,hormones and transcription factors played an important role in the regulation of rhizome growth.