Constructing Of Genetic Linkage Groups And QTL Mapping For Cold Tolerance Relative Traits In Cassava(Manihot Esculenta Crantz)

Cassava (Manihot esculenta Crantz) is the most important tropic crop and a staple food for over600million people, and also one of six biggest staple crops in the world. At present, cassava is considered as an important cash crop in industrial raw materials for industrial use or bio-ethanol in Asia and other countries for poor farmers. It can grow and get yield in drought, barren, and acidic soil and high starch content in root. Because of low temperature lead to low cassava production, cold resistance breeding is one of the main goals of cassava breeding in China. The F1segregative population of235lines between no-inbred parents KU50and SCI24(KS population) was used to construct a molecular genetic linkage map with SSR and SRAP markers, and the KS population was planted in Guilin city and Wenchang city for investigation of cold resistance related traits in year2011and2012respectively. The results are as following:The genetic linkage map has been generated with total of150molecular markers, including72EST-SSR markers,58simple sequence repeat (SSR) markers,20sequence-related amplified polymorphisms (SRAP) markers. The genetic map consisted of21linkage groups and spanned a1434.49cM genetic distance, with the average marker interval being9.56cM. The markers distributed evenly; the largest LG2had18markers, the smallest LG20had two markers. The linkage group length varied from16.89cM (LG20) to139.63cM (LG1), the intervals between markers ranging from0.20cM to47.01cM.The field results for cold resistance phenotypic data:the leaf abscission index ranged form34to97%with mean value of73%; cold resistance index during25and100%with mean value of68%,60%in2011and2012; the average fresh root yield per individual ranged form0.24to4.54kg with average value of1.24kg in Guilin; the average fresh root yield per individual ranged form0.41to5.71kg with average value of2.40kg in Wenchang; the fractional yield ranged form0.11to1.08with mean value of0.54between these two environment; the root dry matter content ranged from20to47%, and ranged from35to48%with mean value of36%and43%in year2011and2012; the starch content between15and39%with average value of30.26%.Inclusive composite interval mapping (ICIM), as implemented in the QTLIciMapping3.2software, LOD=2.5, was applied to idendify QTLs for leaf abscission (LA,2012), cold resistance index (CR,2011and2012), fresh root yield in Guilin (GLY,2012), the fractional yield ranged form0.11to1.08with mean value of 0.54between these two environment; root dry matter content in2011and2012(WDMC,2011and2012), and root starch content (WSC,2011). A total of92QTLs were identified in on fifteen linkage groups for the detected traits.The cold resistance relative traits QTL:a total of38QTLs were detected. For GLA12,11QTLs were detected,3the main effect QTLs phenotypic variation explained (PVE) more than50%; for GCR11, four QTLs were detected, two main effect of QTLs with PVE are33.29%and26.53%; for GCR12, three QTLs were detected, the two main effect of QTLs with29.85%and19.75%; for GWY,20QTLs were detected, for which the PVE ranged form3.55%to48.48%with an average42.76%.There are19QTLs can be reprated, two and three QTLs on the same marker interval that corresponded to three traits.The others traits QTL:a total of54QTLs were detected. For GLY,20QTLs were detected, for which the PVE ranged form26.43%to33.31%with an average value of31.63%; for WCY12,17QTLs were detected, four main effect of QTLs PVE45.62%,46.00%,46.27%and46.40%; for GWY,20QTLs were detected, for which the PVE ranged form3.55%to48.48%with an average42.76%. The six QTLs for WDMC11within2main effect QTLs with PVE22.15%and21.48%; for12DMC, four QTLs were detected, two main effect QTLs with PVE31.63%and26.24%; the7QTLs for SC within2main effect QTLs with PVE21.17%and19.37%.