Hybrid Vigour and Inheritance of Height in Rice

Abstract

PREVIOUSLY¹, while investigating the inheritance of photoperiodic reaction in rice, in this laboratory it was observed that the F₁ plants of the crosses between Aus (summer) and Aman (winter) varieties of rice showed hybrid vigour in respect of plant height, tiller number and grain yield. Earlier workers² also recorded hybrid vigour in the F₁ generation of some rice crosses. However, it is interesting to note that in the present investigation this vigour in one of the growth characters, that is, height, was found to persist in the F₂ generation (Table 1). Mean height of the F₂ plants in every case was found to exceed the mean height of the taller parent. The F₂ frequency distribution in each cross indicated mostly a unimodal curve with transgression beyond the maximum limit reached by parents. It was also observed that the number of the F₂ plants exceeding the maximum limit of the parents was proportionately more in crosses which involved parents with almost the same maximum limit in height, that is, in Patnai–23 × Dhairal and Bhasamanik × Charnock crosses. While in other crosses involving parents with comparable maximum height, as in Patnai–23 × Charnock or in Bhasamanik × Dhairal crosses, the proportion of transgressing segregation in F₂ was less. All these indicate a polygenic inheritance of this character. The proportion of the F₂ plants exceeding the maximum limit of the parents under different crosses suggests that the cumulative effect of the genetic complex influencing the plant height is different in different varieties. Several workers observed the quantitative nature of this character, while monogenic, digenic and trigenic segregations were also reported in some crosses².