No abstract

Estimates of gene action for lodging related traits at Wheat Research Center during 1999-2002 in three crosses of wheat showed different genetic control of the traits among the crosses. For almost all traits, additive or dominance effects or both components were significant in either three- or six-parameter model, indicating that both additive and dominance gene effects were operative for different traits contributing to lodging resistance. Although duplicate type of epistasis was also observed for second internode breaking strength, plant height and spikes per plant and grain yield per plant once in different crosses, additive x additive epistasis along with additive gene action for the aforesaid traits would improve selection of the same in the segregating populations. The additive x dominance gene interaction for second internode length, diameter and wall thickness would be useful too for improvement of second internode breaking strength and consequently lodging resistance, as their inheritance and selection in segregating populations would be relatively easier than the traits controlled by completely non-additive genes. For duplicate type of epistasis biparental mating or recurrent selection followed by conventional selection is suggested.DOI: http://dx.doi.org/10.3329/bjpbg.v20i2.17031

Relationships between the traits associated with lodging resistance in wheat were studied within the period of 1999-2002 at Wheat Research Center, Dinajpur in both F 1 and F 2 generations of a 9 × 9 diallel cross without reciprocal. The genotypic and phenotypic correlation coefficients studied in F 1 and F 2 generations were similar with some exceptions. In both F 1 and F 2 generation, the second internode breaking strength was positively correlated with diameter, wall thickness and unit-stem weight of second internode, and main shoot weight but negatively with plant height and second internode length at both genotypic and phenotypic levels. It was observed from path coefficient analysis in both F 1 and F 2 generations that the second internode unit-stem weight had high positive direct effect on it's breaking strength. Main shoot weight, second internode diameter and wall thickness positively influenced breaking strength through its unit-stem weight. Simultaneous selection for the traits contributing to lodging resistant in semi-dwarf wheat might be effective in the improvement of lodging resistance in bread wheat. Key words: Wheat (T. aestivum L), lodging resistance, genotypic, phenotypic, correlation, path analysis, INTRODUCTIONLodging is a complex event, which is influenced by many morphological and anatomical plant traits such as culm length, basal internode length, culm diameter, wall thickness as well as breaking strength or elasticity of culm tissue, culm density, culm anatomy and chemical compositions of stem and root characters, head density and size etc. with some environmental factors. Lodging may occur in the lower two-three internodes of the plant. Pinthus (1973) observed that the lowest three or four internodal lengths have a greater effect on lodging. Stem lodging of wheat is greatly depends upon straw strength. Study of relationships between some important traits associated with lodging is very much important in choosing a suitable selection criterion for lodging resistance. The ideas about the association of lodging with some plant characters could be better explained through correlation coefficient study. Correlations among morpho-physiological characters are helpful in determining the components of complex traits like biomass, yield, lodging etc., but they did not provide an exact picture of the relative importance of direct and indirect influences of each of the component characters. The breeding strategies differ with the nature of association of these characters. Therefore, the relationships have been further analyzed by phenotypic and genotypic correlation coefficients. Then performed path coefficient analysis to disclose the cause and effects of chain relationships of different contributing characters with the most important character related to lodging resistance in bread wheat. The present investigation was undertaken to study the genotypic and phenotypic correlation and then path analysis for the traits associated with lodging resistance in bread wheat.