Evaluating Heterosis and Combining Ability of Air Cured Tobacco (Nicotiana tabacum L.) Genotypes Using Line × Tester Method

Cytoplasmic male sterile hybrids are rapidly producing and developing. In order to determine general and specific combining ability and hetrosis of air-cured tobacco lines and cultivars، 20 hybrids and 12 parental genotypes were investigated in a ramdomized complete block design with three replications in Tirtash Research and Education Center in 2011. Variance analysis based on line × tester method showed that there were significant differences among genotypes for number of leaves and sugar percent at 5 % probability level and for leaf length and width، stem diameter، yield and nicotine percent at 1 % probability level. The results of general combining ability of lines and testers showed that combining ability in genotypes B. B 16A، Burley TMV3، BA1 and BCE were positive and significant for yield. Therefore، this genotypes can be use as one of the parents in breeding programs to improve yield. Based on the results of specific combining ability، crosses of BA1 × BNC21-3 and Iraburbon × BC21-103 due to positive and significant specific combining ability and heterosis of yield 18% and 5. 3% and B. B16A × BC21-103 and BCE × BNC21-3 due to positive specific combining ability and heterosis of yield 12. 6% and 5. 3% can be used to for production of CMS hybrid tobacco.