Studies On Genetic Relationship, Combining Ability & Genetic Map In Castor-oil Plant

The genetic relationship among 96 castor materials was analyzed with specific SSR markers and non-specific SRAP markers combining with phenotypic data, the combining ability of 21 homozygous materials from which was determined by incompiete bialell cross experiment, and the relationship between parental general combining ability, genetic distance between parents and special combining ability was discussed. The genetic map was constructed preliminarily with YC2×YF181 F2 population. The results was as follows.1. A practical protocal for extracting castor genomic DNA was determined by improving CTAB method, which could efficiently remove polysaccharides, polyphenols and pigments in extracting process to raise quality and yield of DNA.2. The genetic diversity was analyzed on 96 representative castor materials from home and abroad varieties as well as wild materials after integrating phenotypic data of 41 characters, molecular data of 26 SSR markers and 48 SRAP markers to reveal the genetic relationship between the materials. The results showed the narrow genetic background of cultivars and more abundant genetic diversity in wild materials, which suggested that it might be the key to a breakthrough in castor breeding to broaden the genetic basis of parents by use of wild materials. SRAP markers posessed more average number of alleles and average effective number of alleles than SSR markers in revealing genetic diversity.3. The general combining ability ( GCA ) of 21 parents and special combining ability ( SCA ) of 80 combinations were measured with 16×5 incomplete diallel design on the main spike length, main spike capsule number, the 1st branch spike length, the 1st branch capsule number, the 2nd branch spike length, the 2nd branch capsule number, kernel weight and seed oil content.4. The relationship between parental GCA, genetic distance ( GD ) between parents and SCA was discussed. The GD between parents of the combinations with highest SCA was medium to large at 9.97~23, however, not all combinations with the GD within the scope behaved high SCA. The GD between parents should vary with their respective GCA levels for their F1 combinations to have a high SCA level, i.e., the GD should be medium to large for H ( high GCA )×H, H×L ( low GCA ) and L×L combinations and small to medium for M ( medium GCA )×M combinations. With high GCA and far GD from most of the materials , YC1,NSCK2,YC2,YF24-4,YFD.26C were promising parents candidates.5. A castor genetic map was constructed preliminarily with YC2×YF181 F2 population, which included 10 linkage groups containing 51 molecular markers and covered 396 cM of genome , the average distance between markers was 7.76cM. With the average length of 39.6 cM, Each group contained 2-12 markers respectively, the largest of which was 93 cM with a average distance at 7.75 cM and the smallest was 4.3 cM.