Association Analysis Of Agronomic Traits With Molecular Markers In Cassava Dominant Varieties

Cassava(Manihot esculenta Crantz, Euphorbiaceae) is a crop with high heterozygous nature. Cassava hybridization can produce genetic diversity and provide many materials for breeding. But it is difficult to predict the breeding results due to the strong segregation in F1 progenies. For this reason, it will play an important role for breeding to perform genomescan of cassava.In this study, cassava varieties/lines were used as a population and their main agronomic traits were analysed., The genomescan was detected by using SRAP and EST-SSR markers, and the genetic relationship was analysed using software NTSYS. The linkage disequlibrium (LD) was carried out by using software TASSEL. The population structure was analysed by using software STRUCTRE and finally the association analysis between SRAP,EST-SSR and agronomic traits was performed by using GLM and TASSEL.(1) The genomic regions with selection sweep were detected through scanning 19 cassava cultivars by using 145 SRAP markers and 132 EST-SSR markers, and SRAP marker have generated 1471 polymorphic alleles, EST-SSR generated 993 polymorphic alleles. Combining to SRAP and EST-SSR marker data, total of 2464 polymorphic alleles have been generated, and with ratio of 96.2%.(2) Combining to molecular markers and agronomy traits, and cluster analysis 19 cassava varieties, divided into four groups was based on the genetic similarity coefficients. SC205 and progeny ZM8316,ZM8340,ZM8337,F499,SC124,SC8002,SC7, as well as, bread cassava, wen chang red and SC10 belonged to one group; SC205 and it's parents ZM8625,SC8013 belonged to other group; SC6,RY9,F154,SC9 belonged to other group; SC8 belonged to alone.(3) LD was detected to exist in the non-linear combination(different linkage groups) of SRAP and EST-SSR loci using LD analysis with TASSEL, while the loci pairs with p<0.01 accounted for only 0.815% of the SRAP loci and 0.302% of the EST-SSR loci. The result is consistent with the previous report that is cassava hybridization carried out from different flowers of heterogonous strains resulted in the high heterozygous nature and strong segregation in Fl progenies. (4) The markers associated with agronomic traits including fresh weight of tuberous roots, shoot weight, plant height, chlorophyll content of leave and so on, were performed using the association analysis of TASSEL, in which 2 SRAP and 1 EST-SSR markers associated with the fresh weight of tuberous roots,4 SRAP and 1 EST-SSR marker involved in diameter of tuberous roots, and 7 SRAP marker related with plant height, and 7 SRAP involved in the number of tuberous roots,1 SRAP and 1 EST-SSR makers with leaf-chlorophyll content. The wonder allelic variation involved in two agronomic traits (fresh weight of shoot and plant height) was found. They existed in Wen-chang Hong-xin in fresh weight of shoot, and in the SC 205 in plant height.