Short- and Long-eared High-yielding Hexaploid Wheat Cultivars: which has Unexpressed Potential for Higher Yield?

Abstract

This investigation was designed to assess unexpressed potential for high yield and evaluate the sink strength of two high-yielding wheat cultivars: a tall plant with long ears (LE), and a semi-dwarf with short ears (SE). This was done by (1) removing one-third of the ear's distal end (decapitation), thereby inducing the development of additional florets, which usually do not form, on the untouched portion of the ear, and (2) by increasing the competition between the ears and the vegetative tissue's via the application of gibberellic acid (GA). The number of grains increased on the untouched basal spikelets of the decapitated ears in both cultivars. The LE type fully recovered (100%) the number and mass of grains on the untouched portion of the decapitated ear. The decapitated SE type recovered 91% of the grain number but only 80% of individual grain mass. Thus, the total yield (number × mass) achieved by the untouched portion of the decapitated ear was 100% in the LE type and 80% in the SE type. Gibberelic acid treatment increased culm length in the tall LE plants but this did not affect grain number of mass. Conversely, GA had no significant effect on culm length of the semi-dwarf SE type but significantly decreased their total grain yield. This effect was due to a reduction in grain number by 64% of the control, rather than decreasing grain mass. Mean grain mass was not affected by GA in either cultivar. A gradual increase in insoluble sugar concentration (starch and fructan) in the ear peduncle during the first month after anthesis, followed by a sharp decrease later, was found in the control and treated plants of both cultivars. In general, the concentrations of both soluble and insoluble sugars declined as grain filling progressed, except for a noticeable increase in total soluble sugars in the peduncles of the decapitated ears of the LE type. The results of this study suggest that of the two high-yielding wheat cultivars that usually give identical yields, the one with long multispikelet ears (LE) and lighter grains has significantly greater unexpressed potential for high yield than the cultivar with shorter ears (SE) and heavier grains.