STUDIES ON THE DEHULLING OF BARLEY KERNELS WITH SULPHURIC ACID AND ON THE INHERITANCE OF REACTION TO COVERED SMUT USTILAGO HORDEI (Pers.) K. & S. INFECTION IN CROSSES BETWEEN GLABRON AND TREBI BARLEYS

Abstract

The use of concentrated sulphuric acid for dehulling seeds of barley hybrids in order to induce infection by Ustilago hordei (Pers.) K. & S., involved complications which made exact analysis of the reaction of the hybrids impossible. Although the hull showed a high degree of resistance to decomposition by the acid and appeared to afford the embryo sufficient protection against acid injury, there were wide fluctuations in degree of emergence of plants from treated seeds, both of hybrid and parent material. Much of the mortality among treated seeds was due to mechanical injury incurred before treatment. There was considerable seedling injury from infection by Penicillium spp. This was probably augmented by unfavorable germinating conditions. Increased severity of infection by U. hordei, due to the removal of the hull resulted in extreme distortion of seedlings and consequent failure to emerge.Genetic studies were made on the F3 of reciprocal crosses of Glabron, highly resistant, and Trebi, moderately resistant to the form of pathogen used. Infection percentages exhibited by the parents were regained in some F3 lines and the hybrids showed little tendency towards greater susceptibility than the parents. Segregation for reaction to covered smut was not sufficiently clear to establish the inheritance of this character.Slight correlation was demonstrated between smut reaction and height of plant, but none between smut reaction and barbing of awns or earliness of heading. The development of strains combining earliness, smooth awns, and resistance to covered smut should present no great difficulty.