Detection and estimation of trigenic and linked digenic interaction effects in castor (Ricinus communis L.) using 21 generations

The present investigation was undertaken with a view to generate genetic information on gene effects for seed yield and its component traits in castor (Ricinus Communis L.). The experimental materials consisted of twenty-one generations, namely P₁, P₂, F₁, F₂, F₃, B₁, B₂, B₁₁, B₁₂, B₂₁, B₂₂, B_1S, B_2S, B₁ x F₁, B₂ x F₁, F₂ x P₁, F₂ x P₂, F₂ x F₁, B₁ bip, B₂ bip and F₂ bip of two crosses of castor viz., JM-6 x 48-1 (cross-1) and JI-436 x PCS-124 (cross-2). Special scaling tests such as X, Y, Z, (B₁-L₁), (B₂-L₂) and (F₂-L₃) were significant either in cross-1 or cross-2 for most of the traits besides significance of other tests showing the presence of epistasis. The X²(2) value at fifteen degrees of freedom were significant in all the traits in both the crosses supported the presence of higher order epistasis. The X²(3) value at eleven degrees of freedom were significant for all the traits in both the crosses indicating the presence of higher order epistasis and/or linkage. The X²(4) value at nine degrees of freedom were significant in all the traits in both the crosses indicating the presence of higher order linkage. Duplicate type of epistasis was responsible for the inheritance of seed yield and its component traits in two crosses of castor. This is the first report of higher order interaction/linked digenic epistasis using 21 generations in castor.