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Type: Thesis
Title: The physiological and genetic basis of yield improvement in an elite barley line adapted to Australian conditions
Author: Porker, Kenton Dean
Issue Date: 2018
School/Discipline: School of Agriculture, Food and Wine
Abstract: Genetic improvement in yield potential is a primary objective of barley breeding programs. The variety ‘Compass’ represents a step change in yield potential, showing a consistent yield improvement over the malting benchmark variety Commander across different environments. The objective of this study was to identify the physiological and genetic bases of improved yield and adaptation of Compass. Crop development is considered the most important factor affecting grain yield and adaptation in dry land Mediterranean cropping systems. It was hypothesised that the improved yield of Compass was due to differences in the pattern of crop development despite Compass being genetically similar to and derived from Commander. Using partial least regression (PLS) the environmental modulation of flowering time in three elite barley cultivars, Compass, Commander, and Fathom, was described across 35 environments at a range of sowing times commonly used by growers in southern Australia encompassing a wide range of temperature and photoperiod regimes. This analysis gave insight into the subtle responses to changes in temperatures that are not adequately accounted for in current crop simulation models. The results suggested that under short photoperiods, varietal responses to temperature might be equally as important as photoperiod in determining time to flower. Based on field trial observations it was concluded that through selective breeding, breeders have shortened the time to anthesis and the duration of the pre-anthesis phases without compromising yield potential in the variety Compass. Compass had a faster development rate and its improved yield was associated with modest improvements in grain number with heavier grain weight. The development of the Commander x Compass bi-parental mapping population allowed genetic analysis of the quantitative trait loci (QTL) controlling developmental and yield traits. The QTL for developmental traits were predominantly located near the candidate photoperiod response gene (Ppd-H1) on chromosome 2H. The faster development of Compass at May-June sowing dates was due to reduced responsiveness to photoperiod. Although there were QTLs of smaller effect that were independent of photoperiod. Current breeding programs have historically focussed on developing photoperiod-responsive varieties, but the reduced photoperiod sensitivity of Compass suggests an alternative means of improving yield potential. Two QTL identified on 4H and 6H were associated with larger grain weight and it was possible to improve grain weight in cultivars of similar heading time and in contrasting photoperiod sensitivity groups. These results present new findings relevant to improving the yield of barley in southern Australia through understanding of the crop’s photoperiod and temperature responses. The results of this study highlight that breeders should consider selecting for a diverse range of phenology genes and it is possible to improve yield and kernel weight within a narrow flowering range. The results from this study reflect the most up-to-date information on the importance of phenology to yield adaptation in southern Australian environments. This information will assist in developing more accurate flowering models and facilitate further fine-tuning of crop development and yield improvement under the short photoperiods associated with autumn planting dates in southern Australian environments.
Advisor: McDonald, Glenn
Eglinton, Jason
Coventry, Stewart
Fettell, Neil
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2018
Keywords: Crop physiology
crop development
grain yield
yield components
flowering time
yield improvement
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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