| Phosphorus (P) is one of the major problems limiting agricultural production. Brassica napus, one of the important oil crops, needs a mass of P and shows very sensitive to P deficiency. Therefore, studying molecular mechanisms of P efficiency, for developing P efficient cultivars and improving B. napus is an essential approach to the sustainable utilization of P resources. Acid phosphatase (APase) acts an important role in adaption of P deficiency. In this study, a B. napus recombinant inbred lines (BE-RIL, Fio) population derived from the F1progeny of a cross between P efficient cv. Eyou Changjia and P inefficiency cv. B104-2was employed to investigate the secreted and tissues APase activity by hydroponics under different P conditions at seedling stage. And quantitative trait loci (QTL) for these traits were identified. The main results obtained were as follows:1. The phenotypic variation of the parents and BE-RIL under different P conditions: The activity of APase increased intensely under low P condition for long terms, but increased little under low P stress for short terms. There was no significant difference between the two parents in the APase activity of secretion, root and leaf. The activity of APase in all the parts was continuous distribution in the BE-RIL population. And the activity of the APase was:root> leaf> secreted. Correlation coefficients analysis indicates that the relationships among the Apase of different parts were complex. The traits of biomass and P concentration related investigated in the third trial of low P stress for long terms had different effect by the APase of different parts.2. QTL analysis for the related traits:The investigated traits were used for QTL analysis by composite interval mapping (CIM) of software WinQTL Cartographer2.5. Totally,62QTLs for APase and48QTLs for biomass and P concentration related traits were detected. Nine, twelve and forty-one QTLs for APase were obtained under high P condition, low P for short terms and low P for long terms in three times, respectively. Totally,110QTLs were distributed on the whole genomes of19linkage groups, with59on A genomes and51on C genomes. The contribution of the phenotypic variations for these QTLs ranged from6.43%to22.38%, respectively. QTLs of root secreted APase were co-localized with the QTLs of root APase on chromosome A4, A6, A9, C3and C5, indicates the relationship of APase between root and root secreted was proved on molecule level. One LP-specific QTL was detected about APase both in root secreted and root, respectively; two LP-specific QTLs were detected for APase in leaf; on C4, the QTLs for root secreted APase were detected under all of P levels. And many QTLs were detected by others in our lab under different environments about yields, root and phosphate concentration related traits at different stages, were overlap with the QTLs detected in this study. So, these co-localized QTLs detected under muilt-environment may play the importance roles for Brassica napus adapted to phosphate deficiency.3. Comparative mapping between the BE-RIL genetic linkage map and B.rapa, B.olerecea:86B. rapa and62B. Oleracea homologous genes of64Arabidopsis APase isozyme genes were identified. These homologous genes and209SSR, GBM markers were used for comparative mapping between the BE-RIL genetic linkage map and B. rapa, B. oleracea. It indicated that there was good linearity between the BE-RIL genetic linkage map and B.rapa, B.olerecea genomes. Thirteen GBM markers developed from genes involved in P metabolization in Arabidopsis were located in the QTL intervals, and many APase isozyme genes were co-localized with some QTLs on the same homologous region of B. rapa and B. oleracea. These genes and GBM markers are beneficial to further study. |
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