| Rice (Oryza sativa L.) is one of the most important food crops in the world, and its mineral nutrients in rice, such as Fe, Zn, Se, Ca, etc, have key roles to health of consumer. Thus, it is a key method for improving human's mineral nutrition by enriching the necessary mineral element contents in rice. In present experiment, the method of inductively coupled plasma mass spectrometry (ICP-MS) was employed to determinate the contents of K, Ca, Na, Mg, Fe, Zn, Cu, Mn and atomic fluorescence spectrophotometer (AFS) was used to determinate the contents of Se, Ge, As, Hg, Pb and Cd, while colorimetry with phosphate-molybdenum-blue complex was employed to determinate the content of P in milled rice. The contents of 14 elements, including P, K, Ca, Na, Mg, Fe, Zn, Cu, Mn, Se, As, Hg, Pb and Cd in milled rice were obvious differences with fairly normal distributions among different rice genotypes. On average, P, K, Cu, Mn, Hg and Cd contents in japonica rice were visibly higher than those in indica rice, whereas As and Pb contents in japonica rice were significant lower than those in indica rice. Furthermore, milled rice from black brown rice contained relative rich Fe and Se contents, and lower content of As, Hg, Pb and Cd, while milled rice from red brown rice was richer for Zn and Se contents. The contents of Se in milled rice from black and red brown rice were obviously higher than that of milled rice from white brown rice. The content of Zn in milled rice from red brown rice was also visibly higher than that of milled rice from black or white brown rice. However, milled rice from black and red brown rice had the relative lower As, Hg, Pb and Cd contents. In this experiment, 5 wild rice showed that WR-3 had relative dense K, Mg, Fe, Zn, Cu, Mn and Se and low contents of potentially toxic elements of Hg, Pb and Cd. Comparing the mineral contents between brown rice and milled rice, K, Ca, Na, Mg, Fe, Zn, Cu, Mn and Ge in brown rice were significant higher than the contents in milled rice.The relationships among mineral element contents in milled rice, and between mineral element contents and rice quality traits including cooking quality traits (gel consistency, amylose content and alkaline spread value) or nutrient quality traits (aspartic acid, threonine, serine, glutaminic acid, glycine, alanine, cysteine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, proline and protein content) were investigated. The results showed that there were significant correlations among mineral element contents. Significant positive correlations were found between Mg and K, Ca or Na contents. Fe content had significant positive correlations with the contents of K, Ca, Na, Mg, Zn and Mn. Significant positive correlations were recognized between the contents of Zn and Ca, Mg, Mn or Cu. Mn content was significant positive correlated with K, Ca, Mg and Cu. However, Cu content had significant negative association with K and Mg contents. The relationships between mineral element contents and cooking quality traits showed that gel consistency (GC) was significant correlated with P, K, Cu, Mn and Se contents; amylose content (AC) was significant associated with P, K, Na, Mg, Cu and Mn contents; alkali spreading value (ASV) had closely positive relationships with P, Ca, Mg, Mn and As contents. In addition, mineral element contents had obvious correlations with amino acid and protein contents. Mg and Se contents were positive significant correlated with each of 17 amino acid contents. Except between P and cysteine, Ca and methionine or Zn and cysteine, the contents of P, Ca and Zn were significant positive correlated with each of amino acid contents. However, Na content was not correlative with amino acid contents except for aspartic acid of rice. Furthermore, significant positive associations were observed between protein content and Mg, Zn, Cu or Mn content in milled rice, but a significant negative correlation was found between Na content and protein content. The content of aspartic acid had close relationship with As or Hg content. The content of Hg was also positively correlated with leucine content. Significant correlation was observed between Pb content and cysteine or methionine contents. The content of Cd was significant negatively correlated with the contents of aspartic acid, threonine, serine, glutaminic acid, glycine, alanine, valine, isoleucine, leucine, phenylalanine, histidine, arginine, proline and protein except for cysteine, methionine, tyrosine and lysine. The principal component analysis was performed on basis of correlation matrix from 29 traits, including 8 mineral element contents, 3 cooking quality traits, 17 amino acid contents and protein content. Six principal components were extracted to explain 84.50% of the total variation and contained the information provided by original 29 variables according to the principal component analysis.In present experiment, the near-infrared reflectance (NIR) spectra of used to measure the samples of two groups of populations collected and the original data for near-infrared reflectance spectroscopy (NIRS) models were created. With the original databases, the optimum calibration models of K, Mg, P, Zn, Cu, Mn and Se contents were developed by using various mathematical and scatter treatments. The corresponding coefficients of calibrations (RSQ1) were 0.78, 0.74, 0.81, 0.57, 0.56, 0.75 and 0.58, respectively. Fitting equations were monitored with external validation sets, the standard errors of prediction (SEP(C)) for K, Mg, P, Zn, Cu, Mn and Se contents were 177.36, 34.31, 118.69, 5.44, 3.20, 2.35ug/g and 15.01ng/g, with corresponding coefficients of determinations (RSQ2) were 0.66, 0.68, 0.65, 0.39, 0.57, 0.32 and 0.53, respectively. It was demonstrated that NIRS provided convenient and accurate ways to predict the contents of K, Mg and P. This will be advantageous in rapidly determination and general selection for rice resources.
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