Genetic Diversity and Effectiveness of Aluminum Tolerance Breeding Program in Sorghum (Sorghum bicor (L.) Moench)
Anas* and Tomohiko Yoshida1)
(Tokyo Univ. of Agric. and Tech., 1)Utsunomiya University)
Sorghum from Africa and Asia was occupied more than 81% of the total area harvested in the world. However, the most of the soil in these areas are acidic in nature and aluminum has been recognized as a major problem in most of acidic soils. Sorghum is generally not tolerant to high Al saturation in the acid soil. Therefore, some series of experiments were carried out in order to look for the efficient selection and breeding method of Al tolerance in sorghum. Identification of parental germplasm, Al tolerance character and genetic aspects of Al tolerance character were evaluated in this study.
Materials and Methods
Japan, USA, ICRISAT and developed sorghum genotypes were used in this study. SSR markers technology was used to evaluate the genetic diversity among sorghum genotypes.
AL tolerance was determined by hematoxylin staining screening method.
Results and Discussion
Generally, wide genetic background was observed for all sorghum accessions, however genotypes from the same place of collection tended have a close genetic background. All genotypes from ICRISAT (I) were distinctly placed in a different cluster group from the genotypes from Japan (J) (Fig. 1). A correlation between genetic diversity assessed with SSR markers and phenotypic variation in field experiment was significant (Fig. 2).
variation of AL tolerance was observed among sorghum genotypes and could be classified into three groups: (i) tolerant genotypes, (ii) susceptible genotypes and (iii) intermediate genotypes. The same result was also obtained from screening using growth response method. An AL-tolerant genotype was crossed with high yield-susceptible genotypes, and two cycles of selection for Al-tolerance were conducted for heritability, genetic correlation, and genetic gain study. The similar genotypic correlations were observed between AL tolerances vs. dry weight, length of head and days to flowering in two crosses (Table 1). Average of heritability of AL tolerance in two crosses of sorghum was moderately low 0.39. Consequently, low genetic gain of AL tolerance was also observed in all sorghum populations. High allocation of resources in early generations for Al tolerance and high selection intensity of Al tolerance must be applied if higher gain for Al tolerance is to be obtained. An examination of the path analysis revealed that dry weight exerted the greatest influence both directly and indirectly on Al tolerance (Table 2).
Increasing of dry weight and selection of Al tolerance in early generation were more appropriate to maximize the AL tolerance in sorghum. Tissue culture could be used for selection of Al tolerance genotypes at the cell level and direct gene transfer into floret-derived callus using particle bombardment showed GUS gene activities (Fig. 3).(図表省略)