Genetic Effects Of Main Heavy Metals And Their Interaction By Environment In Edible Rice Grain(Oryza Sativa L.)

Analysis on seed, cytoplasmic and maternal genetic effects for the contents of heavy metals such as Hg, As, Cr, Cd and Pb was conducted by using genetic models for quantitative traits of seed in cereal crops. According to incomplete diallel cross design(6 X 5), parents and F| generations derived from six different types of rice varieties (parental lines) were used for this experiment. The main results were as follows.Analysis on genetic variance showed that all the traits of 5 heavy metal contents involved were not only controlled by genes of seed, cytoplasmic and maternal plant simultaneously, but also affected obviously by genetic effects and GE interaction effects. The genetic main effects of Hg contents were more important than others, while As and Cr contents were mainly affected by GE interaction effects, the genetic main effects and GE interaction effects of Cd and Pb contents were almost near. In genetic systems, dominant effects and dominant interaction effects of Hg contents were main, the genetic effects of seed had some effects on it. As, Cr and Cd contents were mainly affects by additive interaction effects of seed and maternal dominant interaction effects, and cytoplasmic genetic effects and cytoplasmic genetic interaction effects also had a important role.The results of heritability and selective response analysis indicated that the contents of Hg, As, Cr and Cd contents was higher, so these four elements had stronger inheritance transfer ability. Large populations were required to decrease their contents, which was helpful to breeding objective in identification and elimination through screening. The contents of Pb had the lowest total heritability in narrow sense. The total selective response of 5 metal elements was 42.08%~131.5%.In order to lower metal contents, we should rely on large populations and proper breeding methods. For Hg, single seed descent method is better; for Cr, single plant selection, while for As, the combination of the two methods mentioned above may be effective to identification and screening.Based on heterosis analysis, it was indicated that Hg, As and Cr contents had positive population means, Pd contents is 25.3% and ranked the first place. Cd and Pb contents had negative population means, among which Cd contents had the highest one of 15.2%. In early season, heavy metal contents had negative population means of GE interaction. In late season, the means were positive except Cd. It showed that the utilization of hybrid heterosis could2significantly help to reduce heavy metal contents especially for Cd.Analysis on genetic covariance proved that genotype covariance was detected to be positive between these 5 heavy metal contents. Genetic covariance and GE interaction covariance were positive or negative to different degrees between pairs of element contents. Different methods of screening and identification were used in breeding program according to genetic relationship which was controlled by different genetic system, in this way the breeding objective of decreasing heavy metal contents can be reached.