Investigations on yield in cereals. VIII. Hybrid vigour in wheat

Abstract

Of the genetic problems upon the solution of which immediate progress in plant breeding depends, hybrid vigour is in the front rank. This is particularly the case in naturally out-pollinating and highly self-sterile plants such as many forms of Brassica oleracea, and some of the pasture plants. But in these, genetic experiment is peculiarly difficult. With some crops, notably maize and the tomato, it has proved practicable and clearly advantageous to grow commercial crops of F₁ plants. Even in the British cereals (all, save rye, highly self-fertile and self-pollinating) there are grounds for believing hybrid vigour to be of some economic interest. A thorough investigation of vigour was therefore made in the cross Little Joss × Thule (both T. vulgare) in the F₁, F₂ and F₃ generations. In addition a range of ninety-four crosses was studied on a small scale. Of these fifty-six were between varieties of T. vulgare, the remainder being interspecies, some with parents of the same chromosome number and some not. "Vigour", variably specified by investigators, was here taken to be yield of grain together with the associated attribute, tillering. Certain physiological experiments were also made on grain weight, germination rate, embryo weight and respiration rate of the germinating grain. The crosses were made reciprocally.