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Abstract

Seed tuber physiological age is known to influence a range of important growth
processes in potato including early vigour of the plant, stem number per plant, hence
tuber size distribution, time to emergence and the rate and duration of canopy cover rate
of the plant. There is also an indication in published evidence to suggest that the
expression of the seed tuber physiological age effects is modified by planting
environment and varies with genotype. Furthermore, current process-based potato
models do not capture the effect of the seed tuber physiological age and the interaction
with planting environment. This reflects the lack of understanding and quantification of
the effect of physiological age on potato growth. This thesis reports on physiology
studies to investigate the effect of seed tuber physiological age and planting environment
on stem number and component processes of pre-emergent growth and canopy
development for important commercial cultivars of potato. The resultant findings are
incorporated into a process-based potato model.
Investigation of a production dataset collected from commercial potato paddocks in
northern Tasmania showed that tuber size distribution was correlated with stem number
per plant. The investigation also showed that planting environment (i.e. location, sowing
date and soil type) varied with stem number. A follow-up controlled-environment trial
provided further confirmation of the interaction between seed tuber physiological age
and planting environment and that the response varies with genotype.
Currently, the lack of any reliable measure of physiological seed age makes it difficult to
develop response functions that can be incorporated into process-based models. With
this in mind, a study was conducted to explore the possibility of using mitotic index as
an indicator for tuber sprouting pattern as affected by seed tuber physiological age.
Physiologically older tubers were found to have a higher mitotic index than younger
tubers. However, mitotic index of the eye bud cannot be used to explain the sprouting
pattern of the seed tuber having different physiological ages. Sprouting pattern was
controlled by a correlative inhibition and availability of soil water.
Pre-emergent growth of sprouts after planting was characterised by an initial period of
slow growth (lag phase) followed by rapid linear growth. The duration of the lag phase
was strongly influenced by temperature. Linear growth of the longest sprout was
significantly affected by the interaction between temperature and water potential and
varied significantly between cultivars.
Physiological age of the seed tubers was found to have a significant influence on the
canopy development of potato. Plants grown from physiologically older tubers were
characterized by more branching on the main stem nodes and smaller individual leaf size.
Leaf appearance rate was affected significantly by seed physiological age with the
response varying with cultivar. In Russet Burbank, leaves generated from
physiologically older seed appeared at a faster rate (39.5 °Cd per leaf or 0.025 leaves per
day degree) than leaves from physiologically younger seed tubers (51.2 °Cd per leaf or
0.02 leaves per day degree). No significant difference was found between treatments for
Atlantic although the first leaf in plants from older seed reached full size earlier ( 46.9
°Cd) than plants from younger seed tuber (75.9 °Cd). Seed tuber physiological age did
not significantly affect the leaf senescence rate. However, senescence commenced
earlier in plants derived from older seed tubers.
The results from the physiology studies were incorporated into a new process-based
growth and development model for potato for use within the APSIM modeling
framework. A conceptual model was developed for the relationship between seed
physiological age, soil moisture and temperature conditions at sowing and stem number.
The complete potato model (APSIM Potato) was calibrated for leaf and stem biomass,
tuber yield and phenology against a dataset collected from commercial paddocks in
northern Tasmania and then validated against a larger independent dataset (48 paddocks)
covering a wide range of growing environments. The model was found to adequately
predict tuber yield (R2 = 80% for 48 observed vs predicted plot).

Item Type:	Thesis - PhD
Authors/Creators:	Ridwan Saleh, I
Keywords:	Potatoes, Seed potatoes
Copyright Holders:	The Author
Copyright Information:	Copyright 2009 the author
Additional Information:	Thesis (PhD)--University of Tasmania, 2009. Includes bibliographical references
Item Statistics:	View statistics for this item

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