Selection-based heritability of resistance to Pythium ultimum in safflower

Damping-off disease caused by Pythium ultimum can kill both germinating seeds and young seedlings and cause considerable damage in safflower cultivation. An estimation of heritability lets safflower breeders determine the most effective method for improving seedling emergence in soils  infected  with P. ultimum, the causal agent of seed rot and damping-off. Two cycles of selection were performed to estimate the realized heritability of resistance to the pathogen in five safflower populations. Undamaged seedlings were selected as resistant individuals and were kept to produce seed. The results showed that selection for two consecutive generations increased the emergence of seedlings in Pythium-infected soil from 46 to 53 %. The heritability estimates varied between 1.72 and 77.66 % over the genotypes and environments, in inverse proportion to the severity of the disease. Estimates of heritabilities showed that genes conferring resistance to P. ultimum in safflower are highly heritable and would respond to selection breeding, particularly in some of the studied genotypes, like Isfahan and Zarghan259. However,  different breeding methods must be explored for other genotypes

Genetic variation of safflower (Carthamus tinctorius L.) and related species revealed by ISSR analysis

Genetic diversity of eight genotypes of Carthamus tinctorius L., two populations of C. oxyacanthus, and one population of C. lanatus was investigated using inter-simple sequence repeat (ISSR) markers. All samples were uniquely distinguished by 10 ISSR primers with 144 bands which generated 100% polymorphism. Furthermore, the ISSR markers could separate three safflower species properly, that highlights the effectiveness of this marker system for phylogenetic studies. The most and least informative primers were ISSR9 (PIC=0.367) and ISSR2 (PIC=0.254), and some primers were more efficient in detecting polymorphism in one species than for the others. Unweighed pairgroup method with arithmetical averages (UPGMA) cluster analysis enabled construction of a dendrogram  for estimating genetic distances among different populations. The result of cluster analysis suggested that cultivated and wild populations of C. oxyacanthus had close relationship with each other and far relationship with C. lanatus. The extreme genetic dissimilarity was observed between genotypes of C. tinctorius and C. lanatus populations. Based on the results, C. oxyacanthus could introduce favorable genes to cultivated safflower via inter-specific hybridization in breeding programs. Nei’s gene diversity index, Shannon’s index and percent of polymorphic loci showed that Isfahan ecotype of C. oxyacanthus had the highest variation at DNA level in relation to populations of other species. The ISSRs developed in this research along with those recently studied by other researchers will contribute to construct genetic map with a density sufficient for safflower molecular breeding