Assessment of inter- and intra-inbred line variability in sunflower (Helianthus annuus) by RFLPs

The restriction fragment length polymorphism (RFLP) between 26 sunflower inbred lines was evaluated with 81 probe-enzyme combinations involving 51 cDNA clones and 4 restriction enzymes (HindIII, EcoRI, EcoRV, and BglII). An average of 4.6 fragments and 4.9 profiles was detected per probe-enzyme combination, across all inbred lines. The RFLPs revealed were characterized by a high percentage (>70%) of multifragment profiles. Nei's average gene diversity was calculated to measure the genetic variability within cultivated sunflower; the average gene diversity computed with 81 probe-enzyme combinations was 0.59. The relationships between the 26 sunflower inbred lines were analysed by estimates of Nei's F index, which ranged from 0.50 to 0.91, as well as Nei's genetic distance, d, which varied from 0.05 to 0.41. A UPGMA (unweighted pair-group arithmetic average clustering) dendrogram was constructed using the genetic distance matrix; likewise, a principal component analysis was performed using the F matrix. The results obtained from the two clustering analyses allowed the separation of maintainer lines (females) from restorer lines (males). After partitioning the 26 lines into a pool of maintainer lines and a pool of restorer lines, the estimation of gene differentiations showed that the absolute difference (Dm) between females and males was only about 5%. Intraline variability was also examined in 4 sunflower inbred lines, using 30 probe-enzyme combinations. Heterogeneity at varying levels was detected in 3 of the 4 lines studied. The RFLPs detected by this set of selected clones in the 26 inbred lines suggests that RFLPs could be very useful descriptors for sunflower inbred line and variety studies.