July-Dec. 2012 CLS & Bolting Resistance Analysis 103 Analysis of Resistance to Cercospora Leaf Spot and Bolting in Sugar Beet as Winter Crop Using Griffing’s Diallel Method and GGE Biplot Mohsen Niazian* 1 , Reza Amiri 1 , Seyed Mohammad Mahdi Mortazavian 1 , Abazar Rajabi 2 , Mohammad Reza Orazizadeh 2 1Former MSc Student of Plant Breeding, Assoc. Professor and Ass’t. Professor of College of Aburaihan, University of Tehran, Iran, Respectively. 2Assistant Professor and Academic Member of Sugar Beet Seed Institute, Karaj, Iran, Respectively *Corresponding Author Address: Associate Professor in Plant Breeding, Department of Agronomy and Plant Breeding Sciences, College of Aburaihan, University of Tehran, Pakdasht, Postalcode: 3391653775, Tehran, Iran Phone/Fax: +98 (21) 36040615 Email Address: ramiri@ut.ac.ir DOI: 10.5274/JSBR.49.3.103 ABSTRACT In order to study the genetics of resistance to Cer- Cospora leaf spot (CLS) and bolting in sugar beet, nine parental lines and their F1 hybrids were formed in a di- allel cross pattern. The genotype main effect plus geno- type x environment interaction (GGE) biplot and Griffing’s method II diallel scheme were used for analy- sis. Combining ability, gene action and heterosis were estimated for these two important traits. The biplot dis- played the most important entry by tester patterns of the data and allowed the information to be extracted vi- sually. Using this technique, different genetic aspects were clearly visualized. The biplot analysis indicated that the first two principal components explained 74% (59% and 15% by PC1 and PC2, respectively), and 75% (42.36% and 32.64% by PC1 and PC2, respectively) of the variation for resistance to CLS and bolting, respectively. Based on GGE biplot presentation and Griffing’s diallel