Variability and Molecular Characterization of Ten Onion Genotypes

Aim: Releasing new varieties mainly depend on evaluation the genotypes in the breeding programs. So, the objectives of this work were evaluating ten Egyptian onion genotypes for producing onion bulbs from sets, assessing the magnitude of genetic variability, heritability and genetic advance and estimating the genetic diversity among the genotypes using molecular markers.

Place and Duration of Study: Study was conducted at Giza Research Station, Giza Governorate, Egypt, at consecutive two seasons.

Study Design and Methodology: The onion genotypes were grown from sets in RCBD with three replications. The mean performance and genetic components of twelve yield related traits were estimated as well as the genetic diversity among these genotypes by using RAPD and ISSR techniques.

Results: The results showed that the high means of leaf blade length and number of leaves/plant were obtained by Giza 20. The high means of fresh leaf blade weight/plant and culls yield were recorded by Shandaweel 1. The high means of total yield, marketable yield and average bulb weight were given by Composite 13, while Giza 20 x Ori gave the high mean of total weight loss (%). Composite 8 and H.Y. 28 recorded the high means of dry leaf weight and number of complete ring/bulb, respectively. The high means of bulb total soluble solids content (%) and bulb dry matter content (%) were recorded by Z218 white. Heritability in broad sense ranged from 0.002 for leaf number/plant to 0.67 for fresh leaf weight/plant. The difference between PCV and GCV percentages ranged between 1.72% for bulb total soluble solids content and 20.76% for number of complete ring/bulb. The genetic advance mean ranged from 0.04 for leaf number/plant to 76.65 for marketable yield. At the molecular level, RAPD and ISSR markers were used to assess the degree of polymorphism among the genotypes. The markers showed genetic diversity remarkably. The ISSR markers gave diversified results than RAPD.

Conclusion: It could be concluded that the new promising genotype composite 13 had the high response to produce bulb onions from sets. Meanwhile, the genotypes H.Y. 28 and Z 218 white had the high bulb quality traits. These results give an insight into the genetic polymorphism and the possibility of their further use in breeding programs.