Relationships between nitrate reductase activity, leaf area and dry weight in hexaploid and octoploid triticale (x Triticosecale Wittmack): A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours in the University of Canterbury

Abstract

Hexaploid triticale (CIMMYT lines '4-41' and '6-113'. and cv. 'Salvo') and octoploid triticale (CIMMYT line '10-121') were grown in a growth chamber, with two levels of nitrate (1 mol m⁻³ and 10 mol m⁻³ ) for 21 days and 49 days. Plants were harvested and leaf, stem and root dry weight leaf area, tiller number and spike dry weight were determined. Leaf, stem and root nitrate reductase activity (NRA) were determined using an in-vivo + nitrate assay. At high nitrate. 49 clay old euploid hexaploids (4-41 and Salvo) produced greater leaf. shoot, and total dry weight and leaf area than the octoploid, which had twice the leaf NRA of the hexaploids. Hexaploids did not differ in leaf or shoot NRA. Root NRA did not vary between lines. All growth parameters (except spike dry weight) and leaf and stem NRA doubled as with increasing nitrate. Positive phenotypic correlations were found between leaf area, leaf dry weight, shoot dry weight, tiller number, leaf NRA and shoot NRA in 49 clay old plants due to effects of nitrate on these parameters. At high nitrate, positive genotypic correlations were found between leaf area and dry weight components, but leaf NRA and dry weight components were negatively associated, (genotypically and phenotypically). Positive genotypic associations were found between stem NRA, leaf area and tiller number. Yield of the four lines (in the field) was not associated with NRA but positively associated with leaf dry weight. Broad-sense heritability of leaf and stem NRA was low at high nitrate (16 and 17% respectively) but moderate at low nitrate (35 and 49% ). Heritability of shoot or root NRA was very low. Leaf area, tiller number, and shoot dry weight had moderate heritability at high nitrate. Leaf NRA did not appear to be a useful selection trait clue to low heritability and non-association with yield. Leaf area, and possibly stem NRA may be useful in older plants. Further trials with more genotypes are required to conclusively evaluate NRA and leaf area as indirect selection criteria for yield in triticale.