| Riceis one of the most importantfood crops in the world, especially in China. With the development of urban and industry, "three wastes" are discharged freely, and chemical fertilizers, pesticidesare abused. These cause heavy metal contamination of arable land. While rice has a strong ability to accumulate cadmium(Cd), "Cd rice" events have been reported by the media in recent years. Cd is a highly toxic elementand heavy metal of the second largest threat to human health after mercury. Therefore, the study of Cd accumulation in rice and QTL mapping are importantto rice breeding. In this study, the material is Single Segment Substitution Line(SSSL) built by our laboratory. Through the detection of Cd in rice grain and substitution fragment contig mapping, the QTL of Cd accumulation related is analysed, and the gene controlling Cd accumulation in rice was tapped fully. These results will be applied to the breeding practice to achieve the safe level of Cd concentration in rice grain.The main results of this study are as follows:(1)In the early season and the late season of 2015, grain Cd concentration of SSSLs was detected. There is a significant difference among rice genotypes in Cd tolerance.Environmental factors greatly impact on grain Cd concentration. Overall grain Cd concentration: early season > late season, Shaoguan heavy metal pollution field> Teaching and experimental base.(2)In this study, a total of 10 QTLs controlling Cd accumulation in rice grain were indentified, which were mapped on chromosomes 1, 3, 6, 7, 8 and 11. Three of the QTLs are low Cd accumulation QTLs, which are q Cd-1-1?q Cd-3-1 and q Cd-8-2 respectively, and seven of the QTLs are high Cd accumulation QTLs, which are q Cd-3-2?q Cd-3-3?q Cd-6-1?q Cd-7-1?q Cd-7-2?q Cd-8-1 and q Cd-11-1respectively. Five QTLs mapped here were likely in commom with QTLs detected in previous studies, and five QTLs mapped here had not previously been detected.(3)The materials donor of high accumulation QTL q Cd-7-1 is W04, so 12 materials(C152-8 to C152-19), which were selected from other polymeric materials and carried W04 donor, were measured Cd concentration of grain in the early season and the late season of 2015.Two seasons test datas showed that grain Cd concentration of these materialsexceeded the national standard except C152-13 and C152-14. Using molecular markers to measure fragments, itwas found that the fragments of C152-13 and C152-14 were 1 on the marker RM3859 and Cd30, which were the same belt type with the recipient W0, while the other 10 materials were 3, which were the same belt type with the donor W04. The result proved that the gene controllinghigh cadmium accumulationon the fragments of C152-13 and C152-14 was replaced by its allele, so C152-13?C152-14 lost ability to accumulate Cd. This study further demonstrates the authenticity of positioning QTL of high Cd accumulation.Meanwhile, the q Cd-7-1 positioned section was narrowed down tobetween the molecular markers RM3859-Cd30. Os NRAMP1 and Os NRAMP5, which are two genes to control Cd accumulation in rice, are within the range of q Cd-7-1, and q GCd7, which is a QTL of Cd high accumulation,has a common part with this range. It proves that q Cd-7-1 is an important QTL.In this study, the mapped QTLs of low Cd accumulation can be used in molecular polymerization breeding, which can reduce the Cd concentration in rice grain under the premise of high yield and good quality of rice; the mapped QTLs of high Cd accumulation also laythe theoretical foundation for the cultivation of low Cd varieties in the future. |
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