Genetic control of early events in protoplast division and regeneration pathways in sunflower

Experiments were conducted to identify the genetic factors controlling prot oplast division and to determine eventual relations between genetic factors involving organogenesis, somatic embryogenesis and protoplast division in sunflower. The present study involved protoplast culture and two traits: to tal division per 100 protoplasts (TOTD) and asymmetric division per 100 pro toplasts (ASYD) were scored in 52 recombinant inbred lines (RILs) from a cr oss between PAC-2 and RHA-266. Asymmetric division is an early event in the formation of embryoids from protoplasts. Analysis of variance indicated th e existence of highly significant differences among parental genotypes and their RILs. Heritability for the two protoplast division parameters (TOTD a nd ASYD) was high (0.87 and 0.89, respectively) and genetic gain expressed as percentage of the best parent for 10% of the selected RILs was significa nt. Twelve putative loci associated with total division per 100 protoplasts were identified. Eleven QTLs were also detected for asymmetric division pe r 100 protoplasts. The QTLs present high significant LOD scores and sum to a high percentage of phenotypic variance. The percentage of phenotypic vari ation explained by each QTL ranged from 2% to 24%. Some segments of the lin kage groups I, XV and XVII are likely to contain genes important for organo genesis, somatic embryogenesis and protoplast division, as clustering of QT Ls for these characters were described. The QTLs identified in these three linkage groups should be involved in cell division and in early events asso ciated with cell differentiation.