The Research Of Forecast On Tobacco Combining Ability And Heterosis Based On Molecular Markers

Heterosis is one of important approaches to increase crop yield and improve quality, and the quick and accurate method to predict the heterosis is helpful to select good hybrids with strong heterosis. Six tobacco parents with different characters were crossed in an dialed mating system in order to evaluate the heterosis and combining ability of the 14 characters. The relationship between genetic distance based on IRAP and ISSR markers and heterosis and combining ability of tobacco was investigated. The results show that:(1) The polymorphisms among the 6 parents were high. 22 marker primers amplified 548 bands, including 437 polymorphic bands (79.74%). With an average of 24.91 bands and 19.83 polymorphic bands. Based on IRAP date the GD between parents varied from 0.187 to 0.717, with the average of 0.423. The GD between G28 and yanyan97 was the lowest and that between K730 and C2 the highest. 17 marker primers of ISSR amplified 334 bands, including 250 polymorphic bands . With an average of 14.71 polymorphic bands (74.85%). 5 marker primers of IRAP amplified 214 bands, including 187 polymorphic bands. With an average of 37.4 polymorphic bands (87.38%).(2)UPGMA cluster analysis was carried out using software BiolD++.The dendrograms was constructed based on the IRAP data respectively. According to the trees the accessions could be clustered into three groups(one of 2 cultivars including BaSmaUovina and K730 ,one of three variety from America and Yunnan and 23 cultivars from America and China )at the levels of D=0.495 by the first classification. At the levels of D=0.285 by the second classification, the accessions could be clustered into 5 groups. Each group divide from the other according as its area , The result indicated that to use UPGMA cluster analysis in tobacco clustering is dependable.(3) Significant correlation between the GD based on IRAP markers and that based on ISSR was found ( r=0.823). Therefore, it can be proved that the genetic differences detected by IRAP and ISSR markers are same ,and the two kinds of markers can be used to detect the GD between parents.(4) combination heterosis analyses indicated that, part combination the Hm and Hb display well, specially had in the nearly 1/3 combination output correlation character to the Hm surpass 15%, in the quality character nicotine has been able to display obviously negative superiority, this indicated that to use the heterosis breeding to reduce the nicotine harm have the extremely vital practical significance.(5)The correlation coefficients between GD based on molecular markers and H_b of each trait except for Stem girth of 15 F1 hybrids were all significant. The correlation coeffcients and H_m of each trait except for leaf conut of F1 hybrids were all not significant.(6) The correlation coefficients between average GD based on molecular markers and general combining ability of each trait except for leaf conut were all positive significant. The correlation coefficients between the GD based on molecular markers and Special combining ability of each trait except for leaf conut were all not significant. The correlation coefficients between the GD based on molecular markers and the total combining ability of 15 hybrids for node distance, leaf area and yield were positive significant, and that for the others were not significant. It was also proved that the GD based on IRAP markers and ISSR markers can be used to predictor some trait of heterosis.