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

Abstract

VII. SummaryOf 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.

Further Studies on and Discussion of the Heterosis Phenomenon

“…According to some authors (ENGLEDOW and PAL, 1934;cf. also DARLINGTON and MATHER, 1949), heterosis is not to be expected among self-fertilizers. Different opinions have been expressed as to the reIation between mode of fertilization and heterosis.…”

Population and selection studies in a Triticum cross

“…T. P. PALMER p. The F2 mean of p is significantly higher than the F8 mean. Engledow and Pal (1934) have reported higher germination in early generations of wheat crosses, while Copeland (1940) has reported higher growth rates of embryos in hybrid than in inbred corn. Some similar effect may account for the high p in the F2 of this cross.…”

The Relation of Embryo Axis Weights to Heterosis

“…On the basis of these, the remaining weights were corrected, as well as could be done, to give the values which would have been obtained if all the samples had been dried at 90°C. 6 Engledow and Pal (1934), working with wheat, concluded that hybrid vigor does not result solely from a greater embryo weight. These authors probably used the entire embryo as the basis for their conclusion.…”