[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater "recharge" areas and low-lying waterlogging and salinity prone "discharge" areas. This thesis examines the perennial legume strawberry clover (Trifolium fragiferum L.) in respect to variability of available germplasm, adaptive strategies and growth habits, and tolerance to waterlogging and salinity. The aim of this research was to gain insight into the suitability of strawberry clover for further development for broader use in discharge areas in southern Australian farming systems. Genetic variation within and between naturalised populations of strawberry clover cv. Palestine collected from five locations in Western Australia was studied in a common garden experiment. Plants from seed collected at each site were grown as spaced plants and 13 morphological traits were measured. Within-population variation was very high presumably due to the outcrossing nature of strawberry clover. In contrast, betweenpopulation variation was generally low with most traits showing 8 – 15 % of the total variation. However, all populations were different from each other. It was concluded that although originally sown as the same cultivar, each of the populations had begun to differentiate into ecotypes more suited to the habitats into which they had been sown. In a similar experiment, the genetic variation within and between eight populations of strawberry clover collected from the Mediterranean Basin and three commercial cultivars was studied. Results were similar to those from the naturalised Western Australian populations. The proportion of between-population variation was a little higher than for the Western Australian populations, ranging from 6 – 40 % of total variation. Variation in the commercial cultivars was similar to variation in the populations from the Mediterranean Basin. From these two studies it was concluded that the high level of variation contained in populations of strawberry clover indicates 4 ample opportunity to use selective breeding to improve upon current strawberry clover cultivars. .... It was concluded that while lucerne was relatively well-adapted to survival in southern Australian farming systems due to its quickly established deep root system, strawberry clover was likely to be less well-adapted but useful in niche areas. The remaining two species of perennial Trifolium were probably not adequately deep-rooted to survive summer drought. Strawberry clover has previously been under-resourced for breeding and development activities. With its tolerance to waterlogging and mildly saline soils, improved cultivars of strawberry clover could prove to be a very useful plant in areas affected by these factors. This thesis has shown there is ample genetic variation in strawberry clover populations to improve agronomic performance as well as salinity and waterlogging tolerance, and its broad adaptability to southern Australian farming systems.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2008|