OTL Mapping And Analysis For The Related Traits Of Photoperiod Sensitivity In Setaria Italica

Photoperiod is a major environment factor affecting plant development, and photoperiod sensitivity of flowering is an important consideration in plant cultivation and breeding. Setaria italica is short day plant and flowering time is affected by photoperiod. Sensitivity to photoperiod limits the potential for successful exchange of germplasm across different latitudes. Therefore, it is vital for Setaria italica breeders to understand the genetic basis of photoperiod sensitivity in their efforts to broaden germplasm resources. It is useful for exploring the genetic basis of photoperiod sensitivity in Setaria italica.In this research, a population of188recombinant inbred lines （F8） derived from Setaria italica B100and Setaria viridis A10cross were developed. A high-density genetic map was constructed using SNP markers. The RIL population was evaluated in two years of four different photoperiod environment. The performance data of photoperiod sensitivity and related traits in RIL population were used for QTL mapping and epistatic analysis. Consistency QTLs were identified using meta-analysis method in Biomercator2.1. Our main objective was to find major consistent QTL across different environment and key chromosome regions on which those QTL were located.The main results in this study were as follows:1. A genetic linkage map containing325SNP markers was constructed based on an F8RIL population with188individuals. The map spanned a total of1410.7cM with an average interval of4.3cM. There are five slightly larger gaps:4_S29₄99_V2-4_S29₅00_V2region of chromosome1,9_S58₈21_V2-9_S59₈22_V2and8_S57₈13_V2-8_S57₈14_V2regions of chromosome3,10_S72₉87_V2-10_S72₉91_V2region of chromosome4,3_S16₃07_V2-3_S16₃05_V2region of chromosome5.2. A total of94QTL were detected in long-day and short-day photoperiod environment for photoperiod sensitivity and related traits using RIL population by composite interval mapping. Out of these QTL,37QTL were detected in short-day,57QTL were detected in long-day. Different QTL were detected in different photoperiod environment. qEP5-15、qLN5-36、qPH5-34and qLW5-36were detected in two photoperiod environment. qEP4-15、qEP4-18、qLN4-13、qLN4-17, qPH4-13、 qLL4-13、qLW4-12and qLA4-12wer only detected in short-day. qEP3-22、qLN3-22、qPH9-13, qLL9-14、qLW9-14and qLA9-14were only detected in long-day. QTL for flowering time, plant height, leaf number, leaf length, leaf width and leaf area, under short-day conditions, were found clustered on chromosome4, while QTL for long-day conditions resided on chromosome3and9. The QTL in the marker9_S63₈57_V2-9_S63₈46_V2region of chromosome3and1_S2₂1_V2-1_S2₃0_V2region of chromosome9were detected associated with photoperiod sensitivity and related traits during long-day. These results indicated that these regions might contain several important photoperiod sensitivity elements.3. The analysis for the main effect QTL in long-day and short-day showed:QTL x environment （Q×E） interaction were significant. It implied that the main effect QTL related photoperiod sensitivity and related traits were affected by environment. A total of4pairs QTL with the significant digenic interaction were detected for photoperiod sensitivity related traits, explained few phenotypic variation. It implied that epistasis for the genetic of photoperiod sensitivity and related traits occupy a certain proportion, but play a smaller role.5. Totally,10"consensus" QTL were obtained for94QTL associated with photoperiod sensitivity and related traits in long-day and short-day, Each "consensus" QTL integrated3to18QTL, with an average of8.5QTL, and related with6traits. Most QTL for related traits were distributed in the same chromosome regions in clusters. For example,10_S67₉04_V2-10_S68₉35_V2,10_S69₉38_V2-10_S69₉58_V2on chromosome4were major regions for photoperiod sensitivity and related traits in short-day environment;9_S63₈57_V2-9_S63₈46_V2on chromosome3were major regions for EP、LN and PH traits in long-day, and1_S2₂5_V2-1_S2₃0_V2on chromosome9were major regions for PH、LL、LW and LA traits in long-day. True QTL for photoperiod sensitivity and relate traits might gather in these marker intervals.