Components of grain yield in wheat : a thesis submitted for the degree of Doctor of Philosophy in the University of Canterbury [Lincoln College], New Zealand

Abstract

Between 1972 and 1976 a series of field experiments were conducted to investigate the factors limiting grain yield in wheat (Triticum aestivum L). Spike population restricted yield when it was below about 500 spikes/m² but once it exceeded 700/m² grain yield declined due to a reduction in the number of grains per spikelet. Irrigation, high sowing rate, and nitrogen fertiliser generally increased spike number but the effects on the number of grains/spikelet were variable, apparently depending on processes related to leaf area index. The semi-dwarf Karamu outyielded New Zealand wheats when spring-sown because it produced more spikelets/spike and more grains/ spikelet than the other cultivars. The superior grain set of Karamu was because more of the distal florets within each spikelet produced grain than in the other cultivars. The results are discussed in relation to cultural practices and plant breeding.