| The recent development of Maize breeding has largely increased the difficulties to make significant accomplishments if the breeders only exploited the temperate germplasm. Both tropic and sub-tropic maize, originated from diversified center, were confirmed to have extensively variation for China and America Maize germplasm. Thus, introduction, utilization and improvement of the exotic germplasm collected from tropic and sub-tropic regions had become an important approach to enhance domestic Maize genetic diversity. However, the characteristics of photoperiod sensitivity extremely limited the utilization of tropic and sub-tropic Maize in the temperate zone. In addition, take into account the southwest maize production, the development and cultivation of photoperiod-insensitive maize inbred lines are not only importance to popularize the hybrids in this region, but also benefit for increasing the yield and quality of hybrid-seeds under the condition of northwest of China, where have predominant environment for Maize production. In the present study, the population between inbred lines Zheng58 (insensitive) and Ya8701 (sensitive) were developed and grown under two different condition, Sichuan (represent short-days) and Beijing (represent long-days), and a systematic researches on the QTL mapping of the traits associated with photoperiod response was carried out in order to provide theoretical and technological references for the application of tropic and sub-tropic Maize to the temperate Maize breeding. The main results are showed as following.1. The major six traits tassel date, silking date, pollen date, anthesis-silking interval, plant height, ear height of 296 F2:3 family lines were surveyed and analyzed under two different regions. The results showed that all traits were significant different among family lines and between the long:days and short-days; photoperiod response coefficient is significant negative correlative with the yield in long-days. These traits could thus be used to measure the photoperiod sensitivity of Maize.2. A total of 296 F2 individuals derived from Zheng58×Ya8701 was used to construct the integrated molecular genetic map by 93 SSRs distributed on all the 10 chromosomes, which spanned the genome of about 1547.4cM with an average of 16.64cM between two markers. The present linkage map was highly consistent with other published maize linkage maps in chromosomes, and it is apparently that the SSR-based linkage can be used for QTL mapping.3. 69 QTL represented 11 traits were detected under long-days and short-days using composite interval mapping(LOD≥2.5), among which 25 QTL were detected in short-days, 31 QTL were found in long-days, and 13 QTL were associated with photoperiod response coefficient. 1～7 QTL have been identified in each traits which were responsible for interpreting 2.2～57.6% of the phenotypic variance individually, and showed additive and partial dominant effect. The distribution of QTL was trend to cluster on some chromosome regions, especially on the 10 chromosomes, while some loci have an effect on several traits simultaneously.4. QTL of growth stage traits have many similar map loci, while QTL of plant height and ear height have few similar map loci with QTL of growth stage traits, which was different from previous results. The reason might be interpreted that the map loci of some common QTL were on the uncovered map position of present map or epistatic gene action decreased the effects of common QTL and these minute effects QTL were difficult to be detected.5. In present study, QTL detected under long days had more sameness as the QTL of photoperiod response coefficient (PRC), which was agree with the result of Moutiq. So we assumed the QTLs detected in long-days should more exactly represent photoperiod response.6. The QTL with little interaction with the environment including major QTL for ASI associated with markers umc1087,nc005,umc1088 and QTL for tassel date associated with marker umc1453 could be used in the marker-assisted selection (MAS) strategy for photoperiod sensitivity. In addition, the QTL overlapped regions should be the key chromosome regions for photoperiod response. The markers bnlg1655, umc1586, umc2180 corresponding to these regions would also be efficient in the MAS strategy.7. Research between photoperiod sensitivity and flower conversion induced by photoperiod was related closely. Through comparing with the synthetic genetic model of flowering time with 62 consensus QTL in maize yielded by Chardon, QTL detected in this study were agree with 14 of 62 consensus QTL regions. Besides, two regions on chromosome 9 and chromosome 10 coincide with the known hot-spot regions. We also presumed that the QTL detected should be associated with the genes of circadian clock complex such as osSOC1, osCCA1/LHY, osPHYC, osZTL and so on.
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