Genetic control of paste viscosity characteristics in indica rice (Oryza sativa L.)

Paste viscosity parameters play an important role in estimating the eating, cooking and processing quality of rice. Four cytoplasmic male-sterile (CMS) lines and eight restorer (R) lines were employed in an incomplete diallel cross to analyze seed effects, cytoplasmic effects and maternal gene effects on the viscosity profiles of indica rice. The results indicated that the viscosity profiles of rice were controlled by the direct effects of the seed, by the cytoplasm and by maternal plant. The seed-direct effects (V(A) + V(D)) accounted for over 51% of the total genetic variances (V(A) + V(D) + V(C) + V(Am) + V(Dm)) for all the traits, suggesting that seed direct effects were more important than maternal effects and cytoplasmic effects. The additive variances (V(A) + V(Am)) were much larger than the dominance variances (V(D) + V(Dm)), which revealed that additive genetic effects were the major contributors of genetic variation for the paste viscosity profiles, and that selection could be applied for viscosity traits in the early generations. Significant cytoplasmic variance (V(C)) was detected for hot paste viscosity (HPV), cool paste viscosity (CPV) and consistency viscosity (CSV). The cytoplasmic effects for these three traits can, therefore, not be neglected in rice breeding. It was also shown that seed heritabilities (h(o)(2)) tended to be larger than maternal heritabilities (h(m)(2)) and cytoplasmic heritabilities (h(c)(2)). Prediction of the main genetic effects for 12 parents showed that CMS lines had highly positive effects on all the traits except for the breakdown viscosity (BDV), and that R lines had both positive and negative effects on the paste viscosity characteristics.