Studies on variation in populations of Dactylis glomerata L.

Populations of Dactylis glomerata were collected from inland and high altitude areas throughout the South Island and compared with commercial samples. Two trials were designed to evaluate the effect of mountain climate and soil infertility on the performance these populations. The growth of 21 populations was compared over a period of one year in a pot trial at an altitude of 1520 m on Mt Cockayne, Craigieburn Range, Canterbury. For the year the highest and lowest yielding N.Z populations differed by little more than 10%. One population, of Mediterranean origin, produced poorly in spring, probably because of frost injury. The commercial and other coastal lowland samples produced fewer culms than populations originating from inland enough to fully evaluate these differences. The main factor limiting cocksfoot growth at this altitude was considered to be the short length of the growing season. Growing conditions during the short summer season were very favourable, allowing high rates of dry matter production. Total dry matter production amounted to 9600 kg ha⁻¹ for the year, about half of which was produced in the six week period following snow melt. In a glasshouse pot trial the growth of 12 populations was compared in an acid subsoil with three rates of phosphate fertilizer. The low level of phosphate was not enough to sustain growth and yield differences between populations were closely related to seed weight. At the medium rate large yield differences between populations occurred. One population, originating from a high altitude, high country yellow-brown earth site, was superior to all others, yielding 50% more than the second highest yielding population, 80% more than the highest yielding commercial line, and 230% more than the lowest yielding population. The superiority of this population was attributed to an ability to absorb phosphate from low soil solution concentrations. At the high rate of applied phosphate yield differences between populations were not significant, but there were significant differences in phosphate uptake. Overall, commercial populations were efficient in phosphate utilization, but inefficient in phosphate uptake when compared to wild populations. Plant aluminium levels were measured and found to be high when phosphate was limiting. At the medium phosphate level differences in aluminium concentration were considered to be a product of, and not the cause of yield differences between populations. There was some evidence that aluminium was interfering with translocation of phosphate from roots into shoots. Lime increased total phosphate uptake and translocation of phosphate into shoots in two of three populations. There was no yield response to lime, probably because of an induced nutrient deficiency. Lime did not affect aluminium uptake, but increased aluminium translocation into shoots. This result was unexpected and requires experimental confirmation