Influence Of Plastic Film Mulching On Sterility Of CMS In B.napus

The male sterility, including NMS and CMS according to genetic models, is exist generally in nature. The CMS is most important approach of utilization. But it is unstable due to its genotype and environment .The unstablity of rapeseed makes it difficult to select its maintainer with high selective pressure ,therefore to influence the heterosis and fertility in F₁ population,to decrease purity of hybrid .It is important to study the sterile stablity of male sterile line in order to utilize heterosis and decrease risk in hybrid producing process.In order to improve the unstablity of male sterile line many solutions, focus on variety breeding such as increased selective pressure and alternative maintainers and cultivation, for example, fertilizer controlling, sowing date, growth hormone spraying, hybrid producing in the North for use in the South, were proposed.The loess plateau Weibei is a major rapeseed planting area with cold climate and high altitude in Shaanxi province .It is not easy to overcome the unstablity of male sterile line by using hybrid producing in the North for use in the South.3131A and 3116C, parents of hybrid Gaza 1 which is main variety in Weibei, were use in this study to implore the influence of plastic film mulching on sterility and agronomical traits of male sterile line of rapeseed CMS .Collusions were drawn in this study as follows:1.Hybrid producing for Ganza 1 is not implore hybrid producing in the North for use in the South because its parent 3131A is strong winter rapeseed. The most difficult problem is 3131A contain many minor genes controlling stability of male sterile line lead to produce many fertile pollen grains when the temperature is below 10 centigrade during differentiation of buds, hence decrease the purity of hybrid. The study showed that plastic film mulching technique could efficiently decrease no. of fertile pollen grain in 3131A ,improve the purity of Ganza 1 .The major reason are that mulching with plastic film could better inter-root moisture and heat situation .2.The pattern of mulching with plastic film is differently effect on speed of leafemergence, agronomical traits, seed yield per plant, hybrid producing yield .It is namely that hole sowing on the plastic film is best, furrow sowing besides and in plastic film is better, furrow sowing is in the end. Pattern of mulching selected is according to integrative factors.The hole sowing on plastic film can improve moisture and thermal situation , harmonize relationship between major factors for yield and inter-root moisture content for utilization because acreage of mulching is best for increase temperature and moisture conservation. But its flaw is need to pull the seedling out plastic film, thus is take more time consumption, because of seed and hole inconsistent in location. The few precipitation is not easy to flow into inter-root in the pattern. So, this pattern is adopted in high altitude regions generally.The furrow sowing besides plastic film is best in collection of water due to its utilization precipitation below 10mm. But this pattern is less water conservation ability than hole sowing. It is easy to control because it is take less time consumption and integrative mach ions for hybrid producing and production nowadays. This pattern is adopted in middle altitude regions.The furrow sowing in plastic film can increase temperature, conserve moisture , increase crop yield after winter because this cultivation can increase soil and surface of leaf temperature ,decrease soil and leaf transpiration ,avoid freeze in winter. It takes more labor consumption and pest controlling, or it is decrease of yield at large degree. This pattern's disadvantage is not utilization in large scale, but its advantage is that sowing date can delay.