The genetic control of sink size traits in pearl millet: from generation means and triple test cross analyses

Sink size traits are the major determinates of grain yield in pearl millet. The genetic architecture of three sink size component traits (panicle length, panicle girth and grain size) were studied using generation means and triple test cross analyses. The plant materials for genetic analysis consisted of two crosses for the generation means, and one cross for triple test cross (TTC) analysis for each of three traits. The genetic populations were developed during the 2005-06 and the field experiments were conducted during the 2006 rainy season and 2007 summer season. Scaling and joint scaling tests revealed that a simplistic additive-dominance model did not adequately explain the observed variation for all the three sink size traits in both seasons, providing an evidence for the presence of epistasis. The six-parameter model and the TTC analyses revealed significance of both additive and dominance gene effects for cross 1 of panicle length, panicle girth and grain size. However, cross 2 of panicle length and panicle girth revealed only additive effect, and of grain size showed the presence of both additive and dominance gene effects. All three types of interactions (additive x additive, additive x dominance and dominance x dominance) were found to be significant in cross 1 of all the traits across seasons using generation means analysis. However, TTC analysis revealed the presence of all types of epistasis for panicle length and panicle girth, and for grain size it revealed the presence of additive x dominance and dominance x dominance (j + l) epistasis. In cross 2, additive x additive (i) interaction alone was significant for panicle length and panicle girth, whereas for grain size, dominance x dominance (l) followed by additive x dominance (j) contributed significantly across the seasons. Breeding strategies for the improvement of sink size traits are discussed based on genetic information obtained.