Genetical Analysis of Resistance to ‘Take-all (Gaeumannomyces graminis var. tritici) T-41 Isolation in Bread Wheat Using Generation Means Analysis

Take-all disease, caused by Gaeumannomyces graminis var. tritici (Ggt) is one of the most important of wheat diseases that causes severe damage to crown and root rot in different regions of Iran. Development of resistant varieties requires genetic study on inheritance and type of gene action in disease resistance, which so far has not been any report in relation to (Ggt). Therefore, in order to genetically analyze of resistance to this disease, the generations of P1, P2, F1, F2, BC1 and BC2 were produced and planted at greenhouse. After artificial infection of plants with T-41 strain of (Ggt), the phenotypic measurement was based on the degree of disease damage and its symptoms on the crown and root were recorded. The results of the generation mean analysis indicated that the five-parameter model can explain the variations between the means of generations in two crosses (1528×164 and 1622×1526) and four parametric models in third cross(1528×1546). Additive, dominance and epistatic effects including additive × dominance and dominance × dominance were exist in controlling of this trait. The dominance and epistatic effects were greater than the others. Distribution of F2 generations, showed a tendency toward susceptibility so the susceptibility was dominant to resistance. Analysis of the F2 data based on the classical ratios showed that with phenotypic grouping of F2 generation in three susceptible, semi-susceptible and resistant groups. These three groups corresponded to the epistatic ratio (9:6:1), respectively. This result was almost consistent with the results obtained from the Generation means analysis, since in GMA, duplicate dominant epitasis and partial duplicate interaction were detected and the minimum number of genes involved in controlling this trait has been estimated by 2 gene that it has a relative accordance by duplicate dominant interaction with additive effect (9:6:1).