Genotypic variability in Yorkshire fog grass (Holcus lanatus L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Agronomy at Massey University

Abstract

Plant to plant genotypic variation in New-Zealand Yorkshire-Fog grass was examined in order to quantify the relative importance of average gene effects, dominance, epistasis and environment. The plant variability was contrasted also against topodeme variation.

Plants were grown under glasshouse conditions (20° - 25°C), using vernalization and sixteen hour daylight to encourage growth and flowering. The confounding effect of bench position was removed by regression adjustment.

Fifty half-sib lines representing ten diverse New Zealand topodemes were examined in a one-way mating design, laid out as a randomized complete block experiment.

In general, half-sib and plant variances were much larger than the topodeme variance. This supports earlier findings that there are no major topodeme differences in New Zealand Yorkshire Fog grass germplasm.

The broad-sense heritability estimates which indicated total genotypic contribution varied from low to high. Most botanical, flowering and tillering characters had medium to high values while the agronomic characters had medium to low estimates.

The attributes with medium to high narrow-sense heritability are several measures of leaf size, tiller development, purple colour, plant height and erectness, flavanols and panicle width. Breeding methods, such as mass selection, line selection, line breeding or simple recurrent selection should ,therefore, be appropriate for these.

The attributes with medium to high heterotic-sense heritability are leaf tensile

strength, leaf hairiness, old disease, flowering period, panicle length and compactness

and several aspects of tiller production. Breeding methods, such as recurrent selection with progeny testing or top cross progeny tests for high specific

combining ability should be useful, including synthetic cultivars and some kinds of recurrent bulks.

Of particular interest was the finding that there was more genetic variability for the duration of tillering and flowering periods than for tiller numbers or flower initiation. There was also evidence that the genetic activity controlling tiller number changed as the tillers aged.