Half-diallel analysis of Aphanomyces root rot (black root) resistance of sugar beet (Beta vulgaris L.)
2010
Taguchi, K., National Agricultural Research Center for Hokkaido Region, Memuro (Japan) | Ogata, N.
Analysis of a set of half-diallel crosses for Aphanomyces root rot (black root) resistance was conducted in sugar beet (Beta vulgaris L.). Five selfed O-type parental lines and ten Fsub(1) lines derived from half-diallel crosses between parental lines were used for analysis. Disease evaluation was carried out in an Aphanomyces infested field in Ikeda-cho, Hokkaido, Japan for two seasons (2004 and 2005). Diallel analysis related to genetic variances and parameters was conducted using 'DIALL' developed by UKAI (1989). In analysis of variance according to Walters and Morton (1978), the additive effect (a) and dominance effect (b) were significant at the 1% level. The (Vsub(r), Wsub(r)) graph indicated that the results showed a good fit to the additive-dominance model in the 2004 season, but in 2005, the slope of the regression line of Wsub(r) on Vsub(r) in the (Vsub(r), Wsub(r)) graph was much lower than 1, suggesting the presence of non-allelic interaction. However, the (Vsub(r), Wsub(r)) graph of the 4 x 4 sub-diallel table resulting from exclusion of the array due to a parent 'NK195' that greatly deviated from the Vsub(r)-Wsub(r) regression line showed a regression coefficient close to 1, indicating the absence of epistasis, also in 2005. The estimate of broad sense heritability was 0.95 in both years, and the estimates of narrow sense heritability were 0.66 in 2004 and 0.83 in 2005. Additive variance was larger than dominance variance. The average degree of dominance was 0.776 in 2004 and 0.523 in 2005, indicating incomplete dominance. The average direction of the dominant gene was minus in both years. In conclusion, the results showed that the resistance of sugar beet varieties utilizing the Fsub(1) hybrid could be improved efficiently by the accumulation of resistant genes and by utilizing the dominance effect.
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