Genetic Variation Of Seed Color And Oil Content And Primary Results Of Population Improvement Of Ya'an Yellow Rape(B.rapa L.)

Ya'an Yellow Rape is a long,widely planted landrace cultivar of B.rapa L.,in Ya'an district,Sichuan Province.It possesses a number of desirable characteristics such as early maturity,strong adaptability,higher yield,high rate of yellow-seeded plant and high oil content,tolerances to barren soils and to dim and wet weathers,favorited by farmers.In this paper,Ya'an Yellow Rape was studied on its genetic variation in seed color and oil content.Over 2003-2007,with field investigations and indoor tests,the seed color types and compositions and the variation in oil contents,as well as the relationship between seed colors and oil contents in Ya'an Yellow Rape were studied.Based on the genetic characteristics of high rate of yellow seeded plants and high oil content,a preliminary population improvement was made to raise the rate of yellow seeded plants and oil content, analysed the preliminary effection.The main results were the following:1.The seed color in Ya'an Yellow Rape can be divided into yellow and brown two types.The plant rate of yellow seed plants to brown seed plants was 77.39%:22.61%.And the rates were changed little in different years.In 2004-2007 the variation range in yellow seeded plants were 76.67%-78.33%,the variation range in brown seeded plants were 21.67%-23.33%,the coefficient of variation was small,indicating that Ya'an Yellow Rape is a stable landrace with high rates of yellow seeded plants,and the rate are generally stable in yellow seeded plant and brown seeded plant.Because the high degree of self-incompatibility in Ya'an Yellow Rape,the stable composition of seed color may related with random mating.2.The oil content of Ya'an Yellow Rape is high.In 2005-2007,we measured the seed oil content continuously,the average oil content of population was 45.93%,varied in 45.73%-46.05%;the highest oil content of single plant was 53.54%.So Ya'an Yellow Rape is a landrace with stable high oil content.3.Analyze the oil content of plants with different seed color indicate that the oil content of yellow seeded plant significant higher than brown seeded plant in Ya'an Yellow Rape.the average oil content of yellow seed plants to brown seed plants was 46.70%: 43.43%,3.27%differ,significant at 1%level.It means significant difference in oil content between yellow seed plants and brown seed plants.With a more careful observation,the color of the yellow seed could be subdivided into 3 types:pale yellow,fine yellow and brownish yellow.The pale yellow and fine yellow seeded plants were main types, accounting to 87.4%whereas the brownish yellow seeded plants were minor type, accounting to 12.60%.No significant different in the three types of yellow seed.4.Ya'an Yellow Rape has wide variation in oil content,the variation range in plants was 36.48%-53.54%;whatever the yellow seeded plant or the brown seeded plant,the variation of oil content are widely.The variation range of yellow seeded plant was 39.82%-53.54%,while the variation range of brown seeded plant was 36.48%-49.04%.It means that Ya'an Yellow Rape has abundant variation of oil content and great genetic improvement potential.The oil content distribution of yellow seed and brown seed was highly overlapped.This implies that there was low oil content individual plant in both yellow and brown seeded plant.It means should not choose yellow seed only when further improve the oil content of this variety,the part of brown seed plant with high oil content should be retained.It's significant in maintaining the genetic diversity.5.Bulk selection was used in preliminary population improvement of target characters (seed color and oil content) of Ya'an Yellow Rape in this study.It's the first report about population improvement in B.rapa L.The results showed that the rate of yellow-seeded plants of C₁-generation was 9.95%than C₀,the genetic gain was 12.98%;the ratio of yellow-seeded plants of C₂ was 6.90%than C₁ and 16.85%than C0_,while the each genetic gain were 7.97%and 21.98%.The rate of yellow-seeded plants was already 93%in C₂-generation.The average oil content of C₁ was 0.92%higher than C₀,the genetic gain was 2.01%;the average oil content of C₂ was 0.69%higher than C₁,the genetic gain was 1.48%.The average oil content of C₂ was 1.61%higher than C₀,the total genetic gain was 3.52%.After two turn bulk selection,the average genetic gain of oil content was 1.76%for each turn in Ya'an Yellow Rape.It means that there's good genetic effect in preliminary population improvement of Ya'an Yellow Rape.The research resuls of C₂ show that there still was variation of oil content in Ya'an Yellow Rape,the variation range was 38.21%-53.52%in plants,so there still has genetic improvement potential of Ya'an Yellow Rape. 6.Near-Infrared seed component analysis(NIRS) and residue weight method were used in the research,the correlation coefficient was 0.9767,Regression coefficient was 0.8549 in the two groups of data by regression analysis;indicate that results of Near-Infrared seed component analysis(NIRS) are highly coincided with the residue weight method,NIRS could instead of residue weight method.But instrument and experimental conditions are easy to influence the result of NIRS.Pay attention and check the representative samples by residue weight method when using.To sum up,Ya'an Yellow Rape possesses a number of desirable characteristics such as high rate of yellow-seeded plant,high oil content,significant different in yellow seed and brown seed,rich genetic variation,great potential for genetic improvement,it's a precious germplasm resources of rapeseed.It deserves more deeply study and use.