EPIGENETIC ROLE OF DNA METHYLATION IN HYBRID VIGOR OF CYTOPLASMIC MALE STERILITY IN SUNFLOWER

Abstract

The molecular epigenetic relationship between DNA methylation and hybrid vigor using different sources of cytoplasmic male sterility of sunflower (six A-lines, three R-lines, and their 18 F1's) has been investigated. Molecular analysis of DNA methylation using methylation-sensitive amplification polymorphism (MSAP), revealed that the used four primers succeeded in characterizing a total of 36 specific loci, 35 out of these loci found to be methylation-susceptible (MSL). Meanwhile, only 27 loci were polymorphic achieving were 77% polymorphism percentage of 77%. Differently methylated regions (DMRs indicated a large convergence between A-lines and single hybrid populations, whereby the percentage of unmethylated state reached 23% and 22% in both populations, respectively. The highest percentage of non-methylated state (31%) was detected in R-lines, whereas the hybrids gave the highest percentage of hemimethylated state (13%) against their sterile maternal lines (Alines) and fertility restorer lines (R-lines) which were 10% and 8%, respectively. A-lines showed the minimum percentage of the internal cytosine methylation (10%), where as, the parental testers and the resulted hybrids gained a slightly higher different percentage (14% and 13%, respectively). The epigenetic distinctness of sterile A-lines was clear as they showed the highest value for full methylation state (57%) against testers and diallel hybrids (46% and 50% respectively). Hybrids like A3XR2 showed a unique methylation pattern to occupy a single cluster. Hybrids with higher hybrid vigor (A2XR1, A4XR2, and A6XR1) gave the highest positive heterosis values for plant yield.