Phenotype Analysis And Gene Mapping Of QTLqCDD3 Associated With Rice Chalkiness Under Drought

In this study,we use a set of segment substitution lines that has been generated by crossing indica rice cultivar 9311 as recurrent parent,japonica rice cultivar Nipponbare as donor.There are three lines qCDD3^Nip-75、qCDD3^Nip-109、qCDD3^Nip-110 were identified that chalky grains increased under drought stress.Phenotypic identification and genetic analysis of QTL related to the formation of rice chalkiness under drought stress,the results as follow:1、Combined with re-sequencing results,we obtained the co-mutated fragment from Nipponbare of qCDD3^Nip-75、qCDD3^Nip-109 and qCDD3^Nip-110 is located on chromosome 3,substitution fragment length is approximately 1.5 Mbp.Then,we get a set of segment substitution lines that has been generated by crossing japonica rice cultivar Nipponbare as recurrent parent,indica rice cultivar Kasalath as donor from Genetics and Development Institute.Screening obtained three lines that the corresponding fragments were substituted(qCDD3^Kas-1、qCDD3^Kas-2、qCDD3^Kas-3), substitution fragment length is approximately 3.6 Mbp.2、Through the phenotypic analysis,on the chalkiness level,the fragment substitution lines qCDD3^Nip-75、qCDD3^Nip-109andqCDD3^Nip-110 were different with 9311 under normal and drought stress,but the difference was more obvious under drought stress; the difference of chalkiness level between qCDD3^Kas-1、qCDD3^Kas-2、qCDD3^Kas-3 and Nipponbare was extremely significant under normal conditions or drought stress. In summary,the QTL was named qCDD3（Chalkiness Degree under Drought）.3、We used the F₂ segregating population generated by crossing 9311 and qCDD3^Nip-110 to get a set of single segment substitution lines qCDD3^Nip-110-1、 qCDD3^Nip-110-3,which have substitution segments only in the 3 chromosome, substitution fragment length is approximately 1.5 Mbp.4、Under the normal conditions,the chalky grain percentage of the qCDD3^Nip-110-1 and qCDD3^Nip-110-3 reached extremely significant levels compare with 9311,and the difference of the chalky grain grade was not significant.Under drought or high temperature stress,qCDD3^Nip-110-1 and qCDD3^Nip-110-3 chalky levels reached significant difference compare with 9311.5、qCDD3^Nip-110-1、qCDD3^Nip-110-3、qCDD3^Kas-1、qCDD3^Kas-3 and parents were grown in Changsha and Hangzhou.The results showed that:The difference is extremely significant between segment substitution lines and parents,that is to say,qCDD3 has practical application value.6、We used the F₂ segregating population generated by crossing 9311 and qCDD3^Nip-110.In finally,qCDD3 was delimited between the marker AS117 and AS85 in 505 Kb intervals combined with the fragment overlapping method.There are 60 genes in it,combined with transcriptome analysis,we speculated qCDD3-3 and qCDD3-5 may be the candidate genes of qCDD3,which lay a good foundation for further cloning of the QTL.