| The breeding and popularization of new varieties play a key role in the progress of agricultural science and technology growth in China.However,the average rowth of several major crops in China has been sluggish since the mid-1990 s.In this paper,rice is used as an example to study the genetic contribution of different resources of germplasm on rice varieties improvement and production by studying the genetic composition of rice cultivars in China.The effects of seed industry reform,genetic diversity on rice production and yield stability were also studied.Basing the conclusion,some suggestions and measurements were put awards to improve the efficientience of crop varieties improvemenet,increase genetic diversity,and to increase crop yield and yield stability.To achieve the above objectives,five sets of data were collected.Firstly,all the name and sowing area of all the popular rice cultivars in the 16 major rice producing provinces were collected in China from 1982 to 2011.Secondly,all the detailed pedigrees of all above popular rice varieties were collected.Thirdly,we collected major agronomic traits of all above popular rice varieties,and planted years and releasing provinces on each major variety.Fourthly,we collected major rice production inputs,such as labor,fertilizer,pesticides,irrigation and other material inputs.Fifthly,we collected the price index,production environment information,such as,drought and flood.Based on the analysis of the pedigree and production information,the contribution of foreign germplasm on the improvement of rice varieties,and the impact of seed industry reform and foreign genetic resources on rice production in China were studied.Finally,the effects of genetic diversity on rice production ands tability were studied too.The main conclusions in this paper demonstrated thatt:(1)Chinese breeders have cultivated the largest number of rice varieties in the world.During 1982-2011,the yield potential and quality of Chinese rice cultivars have been significantly improved,but Its resistance to pests and diseases had declined since the late 90 s.(2)The introduction and use of foreign germplasm resources made great important contributions to the improvement of rice varieties in China.the genetic contribution rates of rice germplasm resources from international rice and Japan to newly cultivated rice was 16.4 % and 11.2% respectively during the period from 1982 to 2011.(3)Compared with the offspring of domestic resources,the yield potential of the international rice germplasm resources was higher,the growth period was shorter,the resistance to rice blast and bacterial blight was stronger;the Japanese germplasm resources and other varieties of germplasm resources of the future generations of rice blast,brown planthopper,white-backed planthopper.(4)There was a significant increase in the number of varieties after the seed industry reformation,however,the quality of seed is not improved significantly.The genetic diversity of rice in China increased significantly,and the distribution of cultivated area was more and more balanced.(5)The relationship between rice yield and the parental coefficient is directly U-shaped.This may explain whether there are positive correlation or negative correlation between genetic diversity and yield.The positive correlation between the parental coefficient and yield variation confirmed that genetic diversity was a prerequisite to ensure stable yield.Based on the above conclusions,this paper recommends some policy suggestions:(1)The government should encourage the discovery、introduction and development of new breeding materials from foreign countries,encrouge the using of new germpalsems for some seed entrepreneurs(2)The government should make some effective and timely measurement to protect genetic diversity to continuously improve crop productivity and stable yield.(3)All the breeding work supported by gorvenment should been stoped.(4)The seed firms should take all the responsibilities of the seed affairs on the base of breeding marketization. |
PDF Full Text Request