| Mineral elements have many cellular and metabolic functions in human health. Mineral element deficiencies lead to the dysfunctions in the human body, and thus affect human health. Improvement of the edible parts of food crops with mineral nutrients would help to alleviate mineral deficiencies in humans. Rice is one of the most important staple foods for human, and thus studies on genetic machanisms of mineral contents in rice were of great significance to improve rice with mineral elements and address the mineral imbalance within the body.In present study, detection of quantitative trait loci（QTLs） for mineral contents in rice was conducted using a BC1F5 backcross inbred line（BIL） population derived from an interspecific cross of Xieqingzao B（XB）//XB/Dongxiang wild rice（DXWR）. The population was grown in Lingshui（LS）, Hainan and Hangzhou（HZ）, Zhejiang, respectively. A set of BC2F4:5 population was established and grown in HZ. QTL mapping for mineral contents in brown rice and four agronomic traits was conducted using the BC2F4:5 population. The main results are as following:1. The contents of six elements in brown rice of the XB //XB/ DXWR BIL population were measured in LS and HZ trials and that in milled rice tested in HZ only. The contents of Mg, Zn, Fe, Mn and Cu elements were measured using ICP-AES and the content of Se measured using ICP-MS, respectively. The results indicated that the avearage contents of the BILs in milled rice were reduced by 65.3%, 64.9% and 58.6% for Mg, Fe and Mn than those in brown rice in HZ trial, while 28.4%, 18.2% and 3.8% for Zn, Cu and Se, respectively. The results of correlation analysis showed that the contents of four elements, i.e., Zn, Mn, Cu and Se, in brown rice were significant positive with those in milled rice, while the remaining two mineral contents did not show significant correlations between brown and milled rice.2. Using a genetic map consisting of 149 DNA markers and spanning 1306.4 c M on rice chromosomes, QTL mapping for mineral contents in rice was performed by composite interval mapping using the Win QTL Cart 2.5. A total of 24 QTLs for mineral contents in rice was identified, including two for both the brown and milled rice, 17 for brown rice only, and five for milled rice only. The phenotypic variance explained by a single QTL ranged as 5.3-16.7% and 5.1-28.2% for the brown rice in the LS and HZ trials respectively, the contribution to the milled rice in the HZ trial was 5.2-56.8%. All the seven QTLs detected for the mineral contents in milled rice and 13 of the 19 QTLs for the contents in brown rice had the enhancing alleles derived from DWXR. Furthermore, 11 of 24 QTLs were not reported previously, which enrich the gene pool for gene conferring mineral contents in rice.Among 24 QTLs identified in present study, 15 of which were clustered in 7 QTL regions of 6 chromosomes. The QTLs for three element contents were located inone QTL cluster distributed on chromosomes 6, and the QTLs for two elements were clutered in six QTL clusters distributed on chromosome 3, 4, 7, 9 and 12, indicating that common genetic-physiological mechanisms were involved for different mineral nutrients.3. The contents of Mg, Ca, Zn, Fe, Mn and Cu in brown rice of the BC2F4:5 population were measured in HZ trial, and heading date（HD）, 1000-grain weight（TGW）, grain length（GL） and grain width（GW） were measured as well. The correlation analysis indicated that showed that Ca content in brown rice was significant negative with HD, GW and TGW, and Mn content in brown rice was significat negative with HD. These negative correlations suggested that improvement of the contents of some mineral elements may result in the decrease in some agronomic traits. Therefore, it should be taken into accounts in rice breeding.4. Detection of QTL was conducted using the BC2F4:5 population with single marker analysis. 37 QTLs for the mineral contents in brown rice and 28 QTLs for HD, TGW, GL and GW were located in 11 segregating intervals distributed on chromosome 1, 4, 6, 8, 9, 11 and 12. Among 34 QTL regions identified for mineral contents in brown rice, 20 were not reported previously. Moreover, the direction of effect of the QTL identified in the remaining 10 marker regions was inconsistent, except that the direction of effect of the QTL in the marker region RM20591-RM340 on the long arm of the chromosome 6 was the same, suggesting that the O. rufipogon alleles beneficial to some traits may have deleterious effects on other traits. Therefore, it is necessary to reduce the unfavourable associations with marker-assisted selection. |
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