bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity analysis of optimal irrigation scheduling using a dynamic programming model
Authors: Tilahun Ketema , Raes D.
Published: September 2002

The problem of designing farm irrigation systems is complicated by the fact
that the return from a project is a function not only of the design variables,
but also of the operation schedules. These operation decisions are not
independent, as irrigation applications at any given time period affect the
entire set of applications to be made in the future. An optimisation dynamic
programming model, CSUDP, was used to analyse the effects of irrigation
levels, yield response factors, and initial soil moisture on irrigation
scheduling. The CSUDP model requires the following as input data: crop
evapotranspiration, rainfall, soil moisture holding capacity, and length of
crop sensitivity stages with corresponding yield response factors. Weekly
irrigation scheduling, which maximises crop yield, was obtained for a given
amount of irrigation water. It has been observed that irrigation scheduling
that takes into account crop sensitivity stages reduces irrigation amounts by
optimally distributing the irrigation water over the growing season. For some
crops, simulation results show that water saving of about 50% resulted
in yield reduction of only 25%. By varying yield response factors
around the values given in literature, it was observed that increasing the
yield response factor of a sensitivity stage decreases relative yield for a
given amount of irrigation water. Though residual soil moisture contributed to
the crop production under limited irrigation water availability, its effect on
irrigation scheduling was found to be limited only to the first 2 sensitivity
stages. This information can be of great importance in optimal irrigation
water management under limited water conditions.
Early growth and development of wild radish (Raphanus raphanistrum L.) in relation to wheat
Authors: Cousens R. D. , Warringa J. W. , Cameron J. E. , Hoy V.
Published: September 2002

Raphanus raphanistrum was grown in monoculture and as a
range of cohorts of emergence in mixture with wheat. Growth and development
were recorded at frequent intervals up to anthesis of the
wheat.R. raphanistrum remained shorter than wheat, only
over-topping the crop prior to anthesis for 2 of 7 sowing dates. When
expressed in terms of photothermal time, growth in monocultures was similar
for all sowing dates except those for wheat in mid-summer. Even a short delay
in R. raphanistrumemergence in mixture decreased its
growth considerably; R. raphanistrum emerging more than
4 weeks after the crop had no detectable effect on the wheat. However, even
R. raphanistrum plants emerging 10 weeks after the crop
produced some seeds. In mixture, R. raphanistrum had a
higher specific leaf area (SLA), reduced leaf partitioning, and taller stems
than in monoculture. A physiological growth model based on parameters from
monocultures was unable to predict growth in mixtures; inclusion of changes in
SLA and height in mixture improved predictions in some cases. It is concluded
that competition models based on monoculture parameters, although previously
successful for species with similar height and phasic development, are
unlikely to work for species that differ in these attributes. Further work is
required on the physiology of plants within mixtures.
Intellectual property, biological diversity, and agricultural research in Australia
Authors: Blakeney Michael
Published: September 2002

This paper examines the impact of national and international intellectual
property and biodiversity laws upon the conduct of agricultural research in
Australia, by both public and private agricultural research institutes. The
paper concludes that implications of these legal developments, for both plant
breeding and plant patenting, counsels the establishment of a coordination
officer responsible for the legal obligations of agricultural research
institutes.
Direct and maternal genetic (co)variances for hogget liveweight and fleece traits in Western Australian Merino sheep
Authors: Cloete S. W. P. , Greeff J. C. , Lewer R. P.
Published: September 2002

(Co)variance estimates for hogget liveweight, greasy fleece weight, clean
fleece weight, clean yield, fibre diameter, and the coefficient of variation
of fibre diameter were obtained for a Western Australian Merino resource
flock. The flock encompassed 16 medium wool bloodlines and data were available
for the period 1982–93. Direct additive genetic variances
(h2) — expressed as a ratio of the total phenotypic
variance within bloodlines — were estimated at 0.52 for hogget liveweight,
0.44 for greasy fleece weight, 0.42 for clean fleece weight, 0.63 for clean
yield, 0.71 for fibre diameter, and 0.62 for coefficient of variation of fibre
diameter. Maternal genetic variance estimates were significant
(P < 0.05) only in hogget liveweight and fibre
diameter, but components within bloodlines were low (0.05 for liveweight and
0.02 for fibre diameter). Direct within-bloodline genetic correlations of
hogget liveweight as well as greasy and clean fleece weight with fibre
diameter were positive (0.17, 0.31, and 0.31, respectively), suggesting that
selection for bigger and heavier cutting sheep would generally lead to a
broader fibre diameter. Liveweight was unrelated to clean yield and negatively
related to coefficient of variation of fibre diameter (–0.17). Greasy
fleece weight was negatively related to clean yield (–0.20). The genetic
correlation of clean fleece weight with clean yield was positive (0.37). Wool
quantity was, in general, positively related to coefficient of variation of
fibre diameter, although the estimated genetic correlations were low (0.12 for
greasy fleece weight and 0.07 for clean fleece weight). The genetic
correlation between fibre diameter and coefficient of variation of fibre
diameter was negative, and fairly low (–0.10). These results are
discussed with reference to sheep breeding.
Fababean (Vicia faba) in Australia's northern grains belt: canopy development, biomass, and nitrogen accumulation and partitioning
Authors: Turpin J. E. , Robertson M. J. , Hillcoat N. S. , Herridge D. F.
Published: September 2002

The growth and yield of fababean (Vicia faba) in
temperate environments has been well described; however, information is
lacking on the response of the crop to the higher temperature and radiation
conditions of subtropical regions. Our aim in this study was to quantify
fababean canopy development, radiation interception, radiation use efficiency,
biomass partitioning, and nitrogen (N) accumulation and partitioning in a
subtropical winter environment and to investigate if parameters describing
these processes were consistent between temperate and subtropical regions. Two
of the most important factors effecting growth patterns and yield in the field
are crop density and water supply. Thus, 2 field experiments were conducted at
Lawes, south-eastern Queensland, over 2 seasons, the first concentrating on
the effect of plant density and the second on varying water deficit, both
using the widely adapted cv. Fiord.
Main-stem nodes appeared at the rate of one node every 54 degree-days (base
temperature 0˚C), with no effect of plant density. With the addition of
each main-stem node, plants produced a constant 5.22 leaves per node until the
start of grain-filling, at which time assimilate became limiting. High plant
density decreased both the number of leaves produced and the size of
individual leaves on later formed branches. Radiation use efficiency values of
1.03–1.29 g/MJ were determined for plants grown under well-watered
conditions, with a lower value (0.83 g/MJ) for a partly irrigated crop.
The measured radiation extinction coefficient was 0.73 for leaf area index
values ranging from 0.4 to 7.5, pooled across experiments and treatments. Leaf
and stem were partitioned in equal proportions until pod set, and the root :
shoot ratio was c. 0.8 at the beginning of pod set. The rate of increase in
harvest index (HI) during pod filling was 0.012/day, except under fully
irrigated conditions in 1999, when HI was much reduced, possibly due to pod
shedding.
Parameters such as the extinction coefficient, partitioning between leaf and
stem, and rate of main-stem node appearance appeared to be quite conservative
in response to density and water deficit, and were within the range of
published values from temperate and Mediterranean environments. This is an
encouraging outcome and suggests that it should be possible to simulate growth
and yield of fababean across the diverse climate zones in which the crop is
grown in Australia by using a single simulation model.
Comparative performance of carbon isotope discrimination and canopy temperature depression as predictors of genotype differences in durum wheat yield in Spain
Authors: Royo C. , Villegas D. , del Moral L. F. García , Elhani S. , Aparicio N. , Rharrabti Y. , Araus J. L.
Published: September 2002

The relationships between carbon isotope discrimination (Δ) in mature
kernels, canopy temperature depression (CTD) during anthesis and grain
filling, 1000-kernel weight (TKW), total carbon content of mature kernels, and
yield were studied in durum wheat (Triticum turgidum L.
var. durum) grown in Spain (western Mediterranean
basin). Twenty-five durum wheat genotypes were grown in 2 regions (NE and SE
Spain) and under 2 water regimes (rainfed v. support
irrigation) from 1997 to 1999 (i.e. a total of 12 trials). Principal component
analysis placed yield and Δ on the same axis. Pearson’s
correlation and stepwise analysis confirmed that Δ was the trait that
best assessed genotype differences in yield within trials, and was followed,
at a considerable distance, by TKW. Our results also demonstrated the
extremely poor performance of CTD throughout the wide range of growing
conditions in this study.
Effects of water deficit on Mediterranean and temperate cultivars of tall fescue
Authors: Assuero S. G. , Matthew C. , Kemp P. , Barker D. J. , Mazzanti the late A.
Published: September 2002

Two glasshouse experiments were carried out to evaluate the morphological and physiological responses to water deficit of Mediterranean and temperate tall fescue (Festuca arundinacea Schreb.) cultivars. In Expt 1, 3 cultivars were studied: 2 temperate cultivars, Grasslands Advance (GA) and El Palenque (EP); and a Mediterranean cultivar, Maris Kasba (MK). Water deficit was induced in containers of 4 plants of a single cultivar by withholding water. In Expt 2, plants of EP and MK were grown together in the same container and received water daily with gradation in intensity of water deficit achieved by varying the daily water ration per container. All cultivars in each experiment exhibited commonly reported responses to water deficit, characterised by diminished evaporative surface area and increased root : shoot ratio. The response of MK was primarily morphological and MK plants had smaller plant size, higher root : shoot ratio, and a lower growth rate compared with temperate cultivars. By contrast, response of temperate cultivars was primarily physiological; stomatal conductance of temperate cultivars was lower and these cultivars had a greater tendency for leaf lamina osmotic adjustment than MK under the most stressful water deficit conditions studied. The morphological adaptations of MK were very effective in delaying the onset of water deficit in Expt 1 when plants were grown with others of the same cultivar, but rendered MK plants uncompetitive and more susceptible to water deficit in Expt 2 where plants of MK where interspersed with plants of a temperate cultivar.
Validation of molecular markers for wheat breeding
Authors: Sharp P. J. , Johnston S. , Brown G. , McIntosh R. A. , Pallotta M. , Carter M. , Bariana H. S. , Khatkar S. , Lagudah E. S. , Singh R. P. , Khairallah M. , Potter R. , Jones M. G. K.
Published: September 2002

Five sets of markers were assessed for their usefulness in breeding, two
linked to wheat stem rust gene Sr2, several markers
linked to a chromosome segment conferring
Yr17/Lr37/Sr38 resistance, two reported markers
for the linked genes Lr35 andSr39,
one for Lr28, and one linked to flour colour. The gene
for Sr2 confers adult plant resistance to stem rust
(Puccinia graminis f.sp. tritici)
and was originally transferred to bread wheat from the tetraploid emmer
(‘Yaroslav’) to the cultivars Hope and H-44. The gene is located
on the short arm of chromosome 3B and confers a durable adult plant resistance
to stem rust usually expressed only in the field. The chromosome segment
carrying the Lr37, Sr38,
Yr17 resistance genes is located on 2AS and was
originally introduced into wheat through an
Aegilops ventricosa
Triticum persicum cross, followed by a cross to the
cultivar Marne (VPM1). The flour colour quantitative trait locus was
originally described in a Yarralinka Schomburg cross and is located on
chromosome 7A. The primers as originally developed required optimisation for
more routine use in a breeding program.
The statistical analysis of quality traits in plant improvement programs with application to the mapping of milling yield in wheat
Authors: Smith A. B. , Cullis B. R. , Appels R. , Campbell A. W. , Cornish G. B. , Martin D. , Allen H. M.
Published: September 2002

It is well known that the response to selection for grain yield is improved
with the use of appropriate experimental designs and statistical analyses. The
issues are more complex for quality traits since the data are obtained from a
2-phase process in which samples are collected from the field then processed
in the laboratory. This paper presents a method of analysis for quality trait
data that allows for variation arising from both the field and laboratory
phases. Initially, an analysis suitable for standard varietal selection is
presented. This is extended to include molecular genetic marker information
for the purpose of detecting quantitative trait loci. The technique is
illustrated using two doubled haploid wheat (Triticum aestivum L.) populations
in which the trait of interest is milling yield.
Using crop simulation to generate genotype by environment interaction effects for sorghum in water-limited environments
Authors: Chapman Scott C. , Cooper Mark , Hammer Graeme L.
Published: September 2002

Multi-environment trials (METs) used to evaluate breeding lines vary in the
number of years that they sample. We used a cropping systems model to simulate
the target population of environments (TPE) for 6 locations over 108 years for
54 ‘near-isolines’ of sorghum in north-eastern Australia. For a
single reference genotype, each of 547 trials was clustered into 1 of 3
‘drought environment types’ (DETs) based on a seasonal water
stress index. Within sequential METs of 2 years duration, the frequencies of
these drought patterns often differed substantially from those derived for the
entire TPE. This was reflected in variation in the mean yield of the reference
genotype. For the TPE and for 2-year METs, restricted maximum likelihood
methods were used to estimate components of genotypic and genotype by
environment variance. These also varied substantially, although not in direct
correlation with frequency of occurrence of different DETs over a 2-year
period. Combined analysis over different numbers of seasons demonstrated the
expected improvement in the correlation between MET estimates of genotype
performance and the overall genotype averages as the number of seasons in the
MET was increased.
Estimation and utilisation of glutenin gene effects from the analysis of unbalanced data from wheat breeding programs
Authors: Eagles H. A. , Hollamby G. J. , Gororo N. N. , Eastwood R. F.
Published: September 2002

Glutenins are a major determinant of dough characteristics in wheat. These
proteins are determined by genes at 6 loci (Glu genes),
with multiple alleles present in most breeding programs. This study was
conducted to determine whether estimates of allele effects for the important
dough rheological characters, maximum dough resistance (Rmax) and dough
extensibility, could be determined from aggregated data from southern
Australian wheat breeding programs using statistical techniques appropriate
for unbalanced data.
From a 2-stage analysis of 3226 samples of 1926 cultivars and breeding lines,
estimates of Rmax and extensibility effects were obtained, first for the
lines, and then for 31 glutenin alleles. Glutenin genes did not determine
flour protein concentration, and this character was used as a covariate.
Rankings of the estimates of Rmax for the alleles were similar to the relative
scores for dough strength reported from previous studies, providing strong
evidence that the analysis of a large, unbalanced data set from applied wheat
breeding programs can provide reliable estimates.
All 2-way interactions between loci were present for 18 of the alleles.
Analyses including interactions showed that epistasis was important for both
Rmax and extensibility, especially between the Glu-B1
locus coding for high molecular weight glutenins and the
Glu-A3 and Glu-B3 loci coding for
low molecular weight glutenins. Because of the complexity of these
interactions, similar values of Rmax and extensibility were predicted for
diverse combinations of alleles. This implied that the practical application
of glutenin genes in applied wheat breeding would be greatly enhanced by
computer software which can predict dough rheology characteristics from
glutenin allele classifications.
Use of tree and shrub belts to control leakage in three dryland cropping environments
Authors: Knight A. , Blott K. , Portelli M. , Hignett C.
Published: September 2002

The water extraction of deep-rooted perennial trees and shrub belts integrated
with annual cropping/grazing systems was studied at 3 sites in the
300–450 mm rainfall zone of the Murray–Darling Basin of
south-eastern Australia. Within 4 years of planting alley farming systems on
cropland, the soil directly below and near the belts had dried the deep
profile. Between 82 and 261 mm of extra soil water storage capacity was
created in the 2.5 to 5.5–6 m profile. At Palamana (the only site
monitored to greater depth), living roots were found 16 m below the surface.
The cumulative water content of the soil to 12 m under the belts was 600 mm
less than of soil cores extracted from nearby cropland. This water storage
difference created under the belts is greater than the largest episodic event
likely in this region and it is therefore unlikely that leakage will occur
directly under or within a few metres of the belts.
The early growth of the belts was rapid and the leaf area of the belts far
exceeded that of remnant mallee eucalypt vegetation. The belts used water that
had accumulated deep in the profile below the annual cropping systems they
replaced. However, the belts only used water from below or within a few metres
from the edge with the adjacent cropland. As suggested by RJ Harper
et al. (2000), a much greater amount of potential
recharge could be controlled if deep-rooted perennials were planted more
closely across the landscape (compared with widely spaced belts). However,
although the belts may be beneficial for the catchment water balance, they
would be commercially unacceptable to farmers. In practice, farmers put the
belts usually no less than 50–70 m apart so that less cropland is
displaced and there is less belt/crop competition. In such cases alley
farming only controls a small percentage of the total leakage, similar to the
amount of crop yield lost by displacement and competition. It would be better
to use a full coverage of perennials on soils where annual systems are the
leakiest, rather than belts across all of the landscape, some of which may not
be very leaky and could be highly profitable for annual cropping.
Leakage could be controlled under cropland in a few years by growing easy to
establish perennial species to retrieve moisture deep in the profile. At
Pallamana the belts utilised 600 mm of accumulated leakage from deep in the
profile in less than 4 years. Based on the average annual recharge rates under
annual cropping (11–35 mm) the land could be cropped again for between
17 and 55 years before that leakage accumulated again.
Adoption pattern of fertiliser technology among farmers in the ecological zones of south-western Nigeria: a Tobit analysis
Authors: Bamire A. S. , Fabiyi Y. L. , Manyong V. M.
Published: September 2002

Using data from a survey of farm operators in two major ecological zones of Osun State in south-western Nigeria, this paper empirically evaluates the determinants of farmers' fertiliser adoption decisions and the intensity of use of the technology using a Tobit regression model. With a multi-stage sampling technique, data were collected with the aid of a structured questionnaire drawn on
180 respondents in the agroecological zones of the State. This was complemented with focus group discussions in
each of the zones. Data were analysed using descriptive statistics and Tobit regression techniques.
A majority of the respondents in the study area are young and energetic but with low literacy level. Mixed
cropping practice was dominant and farming was at a small scale. Large proportions of respondents had extension
contact and were members of associations.
Tobit estimates show that farmers' fertiliser adoption decisions vary with agroecological location, and a
decomposition of the elasticities calculated at the means of the variables revealed that farmers' probability of adoption
and non-adoption accounted for more of fertiliser technology response than did the use intensity, given adoption.
Thus, a policy that increases the quantity of fertiliser made available to farmers in the right form and time will
encourage the adoption and use of the technology in improving the land resource potential.
Improving soil physical fertility and crop yield on a clay soil in Western Australia
Authors: Hamza M. A. , Anderson W. K.
Published: September 2002

In the low rainfall area of Western Australia, clay soils with massive soil
structure form a major part of the area sown to wheat. Yield increases on such
soils have been poor in the last decade compared with those on other soil
types. An experiment was conducted over 4 years (1997–2000) using a
factorial combination of soil ripping to 0.4 m, application of commercial
grade gypsum at 2.5 t/ha, and addition of complete nutrients based on soil
test each year. All crop residues were retained after harvest and returned to
the soil. The experiment was conducted in a wheat–field pea rotation at
Merredin, WA. Soil water infiltration rate, soil strength, bulk density,
water-stable aggregates, cation exchange capacity, and wheat yields were
measured.
Grain yields of wheat and field peas were increased by deep ripping, the
addition of gypsum, or the addition of complete nutrients in some years. The
main treatment effects on yield were additive, as significant interactions
between the treatments on yield were seldom found.
However, all the main treatments also significantly improved many of the soil
physical properties related to crop growth. In 2000, 4 years after the
treatments were applied, soil water infiltration rate was increased by more
than 200%, strength of the topsoil decreased by around 1600 kPa, and
soil bulk density decreased by 20%. Gypsum application increased
water-stable aggregates, but soil mixing caused by deep ripping reduced them.
The combination of soil ripping and gypsum application in the presence of
complete nutrients and annual return of crop residues to the soil is suggested
to improve crop grain yield and soil physical fertility on a range of Western
Australian soils.
Cultivar identification in upland cotton using RAPD markers
Authors: Linos A. A. , Bebeli P. J. , Kaltsikes P. J.
Published: September 2002

Using the random amplified polymorphic DNA (RAPD) method, the identification and the genetic description of 28 upland cotton (Gossypium hirsutum L.) cultivars currently cultivated in Greece was attempted. Based on the results of a preliminary experiment using 50 ten-base arbitrary primers, 24 were selected for the main experiment. DNA bands totaling 181 were observed, 118 (65.2%) of which were polymorphic. On the average, 7.5 DNA bands were amplified per primer, 4.9 of which were polymorphic. The unique identification of all cultivars studied was made possible using 27 specific polymorphic bands (markers) corresponding to 16 primers and a specially constructed key. The genetic similarity of the cultivars was estimated using Jaccard's similarity coefficient, which ranged from 0.614 to 0.922, indicating a relatively narrow genetic base. Cluster analysis by the Unweighted Pair Group Method of Arithmetic means (UPGMA) showed that 21 of the cultivars could be placed into 3 major groups. A similar clustering of the cultivars was obtained using principal coordinate analysis.
Maternal constraint and the birthweight response to mid-pregnancy shearing
Authors: Kenyon P. R. , Morris S. T. , Revell D. K. , McCutcheon S. N.
Published: September 2002

Pregnancy shearing has been shown to increase lamb birthweights. However,
results have been variable between studies. It has been suggested that the
birthweight response to pregnancy shearing is greatest in conditions in which
the unshorn dam gives birth to lambs of low birthweight. This study was
designed to examine the birthweight response under 2 differing maternal
treatments (one designed to restrict fetal growth and the other designed not
to limit fetal growth), with the aim of explaining the variation observed in
pregnancy shearing studies. Mixed aged Romney cross ewes were either shorn
during mid pregnancy (n = 55) or left unshorn
(n = 50). At shearing, ewes were split into
either a ‘maintenance’ group (64 kg at shearing and fed to permit
total ewe liveweight gain equivalent to expected conceptus growth during mid-
to late-pregnancy) (n = 52) or a
‘low’ group (54 kg at shearing and fed to permit total ewe
liveweight to increase at half the expected conceptus growth during mid- to
late-pregnancy) (n = 53), respectively.
Mid-pregnancy shearing was found to increase the birthweights of singletons
(5.6 v. 4.9 kg, P < 0.05) but
not twins, and of lambs born to maintenance group ewes (by 0.6 kg,
P < 0.05), but not low group ewes. Additionally,
mid-pregnancy shearing had no effect on the thermoregulatory capacity of
twin-born lambs.
When the results of this study are considered with those of previous New
Zealand pregnancy shearing studies, they suggest that there are 2 criteria
(and not one, as previously suggested) that must be met to achieve a response
to pregnancy shearing. Firstly, the dam must have the potential to respond
[i.e. have been destined to give birth to an otherwise lightweight
lamb(s)], and secondly, the ewe must have the means to respond (i.e. an
adequate level of maternal reserves and/or level of nutrition to partition
towards additional fetal growth).
On-farm assessment of environmental and management constraints to wheat yield and efficiency in the use of rainfall in the Mallee
Authors: Sadras Víctor , Roget David , O'Leary Garry
Published: September 2002

The responses of wheat grain yield to soil properties, weather, root diseases,
and management practices were investigated in 75 grower-managed crops in the
Mallee region of South Australia, Victoria, and New South Wales during 3
growing seasons. Fourteen cultivars were represented in the sampled crops,
with Frame being the most common (56%). The most widespread crop
sequence was wheat after pasture (43% of wheat crops), followed by
wheat after fallow or cereal (both about 20%); 12% of the wheat
was sown after legumes. Wheat after cereal was more common in drier sites, and
wheat after fallow in wetter sites.
Wheat yield was proportional to Fischer’s photothermal coefficient
around flowering, and ranged from nil to 4.7 t/ha. On average, wheat crops
sown after cereals yielded 0.4 t/ha less than their counterparts sown
after fallow, and 0.7 t/ha less than those after legumes. Sowing date
ranged from 24 April to 21 July; yield declined with delayed sowing at an
average rate of 17 kg/ha.day. Growing season rainfall
(April–October) ranged from 111 to 266 mm, and accounted for 27%
of the variation in grain yield. Soil water content at sowing (0–1 m)
ranged from 32 to 330 mm; yield increased with initial soil water at an
average rate of 6 kg/ha.mm. Grain yield per unit growing season rainfall
was generally low, with 75% of crops producing <12 kg
grain/ha.mm; the maximum ratio was 21 kg/ha.mm. Soil constraints,
including sodicity, alkalinity, salinity, and boron toxicity, reduced yield in
part by reducing availability of stored soil water. Owing to severity of
chemical constraints increasing with soil depth, grain yield and yield per
unit growing season rainfall were both inversely related to the proportion of
water stored deeper in the soil (0.5–1 m). Yield was unrelated to
nitrogen, both initial and applied. Larger amounts of nitrogen accumulated in
soils with more severe constraints partially accounted for the lack of
association between yield and nitrogen.
Environmental and genotypic control of time to flowering in canola and Indian mustard
Authors: Robertson M. J. , Asseng S. , Kirkegaard J. A. , Wratten N. , Holland J. F. , Watkinson A. R. , Potter T. D. , Burton W. , Walton G. H. , Moot D. J. , Farre I.
Published: September 2002

The timing of flowering in canola (Brassica napus) is an important determinant of adaptation to its environment. Cultivars of canola varying in maturity are grown over a wide range of photoperiod and temperature conditions in Australia. A quantitative understanding of the genotypic and environmental control of time to flowering can be used to improve breeding programs and crop management strategies. Controlled environment and field studies were used to determine the responses of 21 cultivars of canola and breeding lines of Indian mustard to vernalisation, temperature, and photoperiod. The number of days to flowering in all genotypes was reduced in response to vernalisation and long days, due to a reduced duration between sowing and buds visible. The vernalisation response was saturated with c. 25 days at 3°C. Base and optimum temperatures for development were confirmed at 0 and 20°C, respectively. The photoperiod response occurred between 10.8 and 16.3 h, and plants responded to photoperiod from emergence. A simulation model incorporating these effects was developed, which predicted days to flowering with a mean deviation of c. 5 days. Later flowering genotypes had model parameters that indicated greater responses to vernalisation and photoperiod than early-flowering genotypes.
Analysis of line x environment interactions for yield in navy beans. 1. Components of variance
Authors: Butler D. G. , Redden R. J. , DeLacy I. H. , Usher T.
Published: September 2002

Multi-environment yield trials of navy bean
(Phaseolus vulgaris L.) lines were grown over a diverse
range of locations for the years 1983–1989 in Queensland, in an
unbalanced set of line × location × year combinations. This is the
first in a series of 3 papers reporting different perspectives on the genotype
× environment (G×E) interactions in this series of experiments. In
this paper, restricted maximum likelihood (REML) estimates of G×E
components of variation were derived using trial means in both standard and
extended models where concomitant genotype and location factors such as
maturity, disease resistance, and experimental management regimes were
investigated. Prior to estimating the variance components the heterogeneity of
trial error variances was modelled. Several alternative trialing systems were
compared using acceptance probabilities derived from the variance components.
The interaction of genotype maturity with location considerably reduced the
line × location × year variance component and further examination
of the maturity × environment interaction suggested an advantage in
stratifying the breeding program on maturity. There is no redundancy in the
current trialing system and an increase in sampling locations can be
justified.
Effects of Neotyphodium lolii infection and sowing rate of perennial ryegrass (Lolium perenne) on the dynamics of ryegrass/subterranean clover (Trifolium subterraneum) swards
Authors: Quigley P. E.
Published: September 2002

There is no clear rationale for use of endophyte-infected or endophyte-free
seed of perennial ryegrass when sowing pasture in Australia. This research was
undertaken to clarify the importance of ryegrass endophyte in temperate
pasture systems. A field experiment was conducted to study the dynamics of
perennial ryegrass/subterranean clover swards in response to
(a) endophyte infection in perennial ryegrass seed,
(b) the sowing rate of this seed, and
(c) the cultivar of subterranean clover. A higher
density of perennial ryegrass seedlings established from seed infected with
the endophyte Neotyphodium lolii (E+) than with
endophyte-free (E−) seed and there was a significant interaction with
the sowing rate. At the highest sowing rate of 16 kg/ha, about 25%
more seedlings emerged in the E+ than the E− treatment. The size of
individual ryegrass plants at establishment was reduced as sowing rate
increased, but endophyte had no effect on their size. The slopes of the curves
describing ryegrass tiller density relationships with sowing rate were similar
for both endophyte treatments in the first 2 years but were different in the
third year. Between the first and third years, tiller density in the E+
plots sown at the lowest rate increased by up to
1000/m2, whereas in E− plots the corresponding
increase was only 250/m2. Such changes have not
previously been demonstrated. This difference is believed to be due to the
superior ability of E+ plants to recover after extended dry periods. At
higher sowing rates, neither endophyte treatment led to increased tiller
densities between the first and third years. The presence of
N. lolii had no effect on plant density of subterranean
clover during the 3 years of the experiment. In the second year, the 3 clover
cultivars tested had similar patterns of reductions in plant density in
response to increased sowing rate of the ryegrass in the previous year, but
these patterns did not persist into the third year. Although dry matter (DM)
yield of herbage in the third year was not responsive to initial sowing rate,
the E+ treatment was still significantly higher than the E−. The
cultivar of subterranean clover had little effect on companion ryegrass, and
total DM production was insensitive to cultivar of clover. The use of
endophyte-infected seed is desirable in order to maintain long-term density of
perennial ryegrass in sheep-production systems in Australia.
Laboratory screening for allelopathic potential of wheat (Triticum aestivum) accessions against annual ryegrass (Lolium rigidum)
Authors: Wu H. , Pratley J. , Lemerle D. , Haig T.
Published: September 2002

A new screening bioassay, the ‘equal-compartment-agar-method
(ECAM)’, was developed and employed to evaluate 92 wheat cultivars for
their allelopathic activity on the inhibition of root growth of annual
ryegrass (L. rigidum). Results showed that the
allelopathic activity of wheat was associated with the sowing time of ryegrass
seeds, the number of wheat seedlings, agar quantities, and agar
concentrations. The addition of activated charcoal into the agar medium
significantly alleviated wheat allelopathic inhibition on the root growth of
ryegrass, indicating that wheat allelopathic activity is chemically driven.
There were significant differences between wheat cultivars in their
allelopathic potential at the seedling stage on the inhibition of root
elongation of annual ryegrass, varying from 23.98% to 90.91%.
Re-screening of 22 selected wheat accessions showed that the allelopathic
potential of wheat cultivars is consistent between different years under the
same experimental conditions. This newly developed screening bioassay
successfully separated the allelopathic effect from the competitive effect
between wheat and ryegrass plants, and enabled the constant release and
accumulation of allelochemicals from living wheat seedlings into the growth
medium to affect the growth of ryegrass. The influence of microorganisms was
also avoided because of the sterile conditions. The present study describes
this new bioassay suitable for the efficient screening of a large number of
wheat cultivars under laboratory conditions.
The vulnerability of Australian horticulture to the Queensland fruit fly, Bactrocera (Dacus) tryoni, under climate change
Authors: Sutherst Robert W. , Collyer Ben S. , Yonow Tania
Published: September 2002

The vulnerability of horticultural industries in Australia to the Queensland
fruit fly Bactrocera (Dacus)
tryoni under climate change is examined. Vulnerability
is defined in terms of sensitivity and adaptation options. Regional estimates
of fruit fly density are fed into an economic model that takes account of
costs of damage, management, regulation and research. Sensitivity analyses are
used to estimate potential future costs under climate change by recalculating
costs with increases in temperature of 0.5˚C, 1.0˚C and 2˚C. It
is assumed that irrigation will automatically compensate for any changes in
rainfall.
The current national, annual cost of Queensland fruit fly is estimated to be
$AU28.5 million/year ($25.7–49.9 million), with
60% of the cost borne by commercial growers. Climatic warming threatens
the sustainability of area freedom in the Fruit Fly Exclusion Zone (FFEZ) and
is likely to increase damage and control costs to commercial growers in
endemic areas, except in northern Australia. Costs to mainland apple, orange,
and pear growers are estimated to increase by $3.1, $4.7, and
$12.0 million with increases of 0.5˚C, 1.0˚C, and 2˚C,
respectively. These represent increases of 25%, 38%, and
95%, respectively, but do not reflect the greatly increased risks of
failure to maintain area freedom in the FFEZ. Growers in endemic Queensland
fruit fly areas can expect their costs to increase 42–82%,
compared with 24–83% in the FFEZ. Increased damage to backyard
growers is likely, especially in South Australia and Victoria. Thus the fly
poses a real threat to southern States under modest projected increases in
temperatures. The extent of the likely cost increases raises questions about
the industries’ ability to pay and remain competitive.
The current analysis illustrates the potential benefits of taking a national
and strategic approach to the management of insect pests in Australia. A
combination of CLIMEX modelling, sensitivity analysis and mapping provided
valuable insights into both industry and regional vulnerabilities. Adaptation
options require further quantification, but that awaits a credible population
model of Queensland fruit fly. Costs need to be discounted, depending on the
expected timing of the temperature increases.
Factors influencing dystocia and prediction of dystocia in Angus heifers selected for yearling growth rate
Authors: Arthur P. F. , Archer J. A. , Melville G. J.
Published: September 2002

Data on 914 Angus heifers and their calves that had been selected for yearling
growth rate (from birth to 1 year of age) were used to
(i) evaluate the effect of dystocia on subsequent cow
and calf performance, (ii) identify factors influencing
dystocia, and (iii) develop and validate equations for
predicting dystocia. Records on heifers born in the high, control, and low
growth selection lines from 1975 to 1990 and their calves were used. Calving
was classified as normal (no assistance), with a code of 0, or difficult
(requiring assistance), with a code of 1. The incidence of dystocia was
4.5%, 9.7%, and 6.2% in the high, control, and low lines,
respectively, with the difference between the high and control lines being
significant (P < 0.05). Dystocia resulted in a
significant reduction in calf survival to weaning (97% for normal
v. 85% for difficult calvings). Of all the
calving and pre-calving traits studied, the ratio of calf birth weight to
heifer weight accounted for the highest variation in dystocia in the control
(19.6%), low (15.2%), and high (5.4%) lines. The total
variation explained by models generated by stepwise regression and
discriminant analyses ranged from 5.4% to 36.8%. Prediction
equations developed by discriminant analysis using traits measured prior to
calving had high accuracy of predicting normal calvings
(72.6%–90.3%), when tested on independent data sets.
However, the sensitivity (ability to identify those heifers having difficult
birth) of the equations was low (0%–40%). These results
imply that the approach to be used to reduce dystocia and minimise its effects
is to develop an overall management strategy involving both planning of mate
selection at joining and supervision at calving.
Yellow lupin (Lupinus luteus) tolerates waterlogging better than narrow-leafed lupin (L. angustifolius) I. Shoot and root growth in a controlled environment
Authors: Davies C. L. , Turner D. W. , Dracup M.
Published: September 2002

We studied the adaptation of narrow-leafed lupin
(Lupinus angustifolius) and yellow lupin
(L. luteus) to waterlogging because yellow lupin may
have potential as a new legume crop for coarse-textured, acidic,
waterlogging-prone areas in Western Australia. In a controlled environment,
plants were waterlogged for 14 days at 28 or 56 days after sowing (DAS).
Plants were more sensitive when waterlogged from 56 to 70 DAS than from 28 to
42 DAS, root growth was more sensitive than shoot growth, and leaf expansion
was more sensitive than leaf dry weight accumulation. Waterlogging reduced the
growth of narrow-leafed lupin (60–81%) more than that of yellow
lupin (25–56%) and the response was more pronounced 2 weeks after
waterlogging ceased than at the end of waterlogging. Waterlogging arrested net
root growth in narrow-leafed lupin but not in yellow lupin, so that after 2
weeks of recovery the root dry weight of yellow lupin was the same as that of
the control plants but in narrow-leafed lupin it was 62% less than the
corresponding control plants. Both species produced equal amounts of hypocotyl
root when waterlogged from 28 to 42 DAS but yellow lupin produced much greater
amounts than narrow-leafed lupin when waterlogged from 56 to 70 DAS.
The fate of residual nitrogen fertiliser applied to a ryegrass (Lolium perenne L.) seed crop
Authors: Cookson W. R. , Rowarth J. S. , Cameron K. C.
Published: September 2002

Large amounts of the nitrogen (N) fertiliser applied to ryegrass seed crops
remain within the soil at seed harvest and can potentially affect subsequent
pasture production and environmental contamination. The fate of residual
urea-15N-labelled fertiliser and the effect of previous
fertiliser application on subsequent leaching losses and pasture production
was assessed during a 9-month period after seed harvest using monolith
lysimeters (diameter, 180 mm; length, 300 mm) in Canterbury, New Zealand.
Results indicated that leaching losses and pasture uptake of residual
15N-labelled fertiliser were largely restricted by the
immobilisation of 15N-labelled fertiliser into soil
organic pools and the expanding root mass. Most of the
15N-labelled fertiliser remaining in the soil 9 months
after the seed harvest was present within the humified organic matter
(50%) and microbial biomass (40%) pools; the majority
(62%) was anaerobically mineralisable. The
15N-labelled fertiliser that became available was
largely recovered in rapidly expanding ryegrass roots, which increased
3–4-fold between seed harvest (December 1997) and pasture harvest
(September 1998). Root mass, soil mineral N, and soil microbial biomass N were
significantly (P < 0.05) greater in fertilised
treatments than in controls at pasture harvest; clay-fixed N, anaerobically
mineralisable N, and total N were not affected. The results indicated that, in
the short term, N mineralisation rates were increased by previous fertiliser
application but there was little evidence of a longer term effect on N
mineralisation rates.
Effect of grazing intensity and cultivar on morphology, phenology, and nutritive value of subterranean clover II. Nutritive value during the growing season
Authors: Ru Y. J. , Fortune J. A.
Published: September 2002

With the decline in pasture quality in southern Australia, the development of
management strategies to improve nutrient supply for grazing animals is
essential and requires a clear understanding of the interaction between
animals and plants. The impact of grazing intensity on the morphology of
subterranean clover was previously examined. This paper reports the effect of
grazing intensity on the nutritive value of subterranean clover, and the
variation in quality of cultivars during the growing season.
Grazing intensity influenced nutritive value and interacted with cultivar
maturity. Heavy grazing depressed dry matter digestibility (DMD) by 5
percentage units in October for early maturity cultivars but increased DMD by
3 percentage units in September for mid maturity cultivars. The influence of
grazing intensity on nitrogen content was small. Heavy grazing did not affect
acid detergent fibre for the early maturity group, but depressed it for the
mid maturity group throughout the season. Acid detergent lignin remained
comparable for all cultivars during the season. Mineral content of
subterranean clover showed variable response to grazing treatments.
Nutritive value varied among cultivars within each maturity group. DMD ranged
over 53–64%, 44–62%, and 45–53% for
early, mid, and late maturity groups, respectively, at the end of the growing
season. The cultivar rank in all nutritional parameters changed with the
progress of the season. The large ranges in the decline rate of DMD within
each maturity group during the last 8 weeks of growth gave an indication of
the potential quality of the cultivars during late spring and early summer.
Despite the variation in mineral content there were no cultivars in which the
concentration of minerals was below the minimum requirements of sheep. These
results indicate that there is a potential for the selection of high quality
cultivars within a breeding program, and that indicative targets of grazing
intensity need to be further developed with a focus on pasture quality.