bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal variation of carbon assimilation in mango (cv. Kensington Pride): effect of flowering treatments
Authors: González Alonso , Blaikie S. J.
Published: August 2003

In the tropics of northern Australia the mango cultivar Kensington Pride exhibits erratic flowering and fruiting and low productivity. Two treatments to manipulate flowering were applied. The first, mango flowering treatment (MFT), involved cutting a cincture through the bark around the circumference of the tree trunk and tying into the cincture a length of twine soaked in a solution of morphactin, CF125. The second involved applying paclobutrazol (PBZ) as a soil drench around the trunk of the tree. Phenology, leaf gas exchange, and fruit yield were assessed over 2 seasons in 3 separate groups of trees in commercial orchards near Darwin.Both MFT and PBZ supported earlier and/or more intense flowering in the season of application than did control trees. The PBZ was re-applied annually and the beneficial effect on flowering occurred in successive years. The MFT was applied once only at the start of the experiment and the effect of MFT was not evident in the second season.The effect of MFT on gas exchange was characterised by a severe reduction in net carbon assimilation (Amax), stomatal conductance (gs), and transpiration (E) for up to 4 months following treatment. Trees receiving PBZ generally had higher rates of leaf gas exchange than MFT trees but similar to control trees. During the dry season, leaves of MFT, control, and PBZ trees had similar rates of Amax. In the year of application, chlorophyll content of MFT trees was lower than that of the other treatments, but in the second year it was very similar to control trees. PBZ trees had the highest chlorophyll content during the study. Commercial fruit yield of PBZ-treated trees was 2–3 times higher than that of control or MFT trees. Independent of the flowering treatments, Amax followed a seasonal trend with an average rate of 9.05 μmol/m2.s (min. 4.42, max. 13.2) during the wet season (January–April), and 4.2 μmol/m2.s (min. 1.11, max. 8.7) during the dry season (May–October). Regression analysis demonstrated that 82% of the variation in gs and 76% of the variation in Amax could be explained by the effect of vapour pressure deficit of the leaf (VPDL) in field-grown mango trees.
Variation among Australian accessions of Vigna vexillata for traits of agronomic, adaptive, or taxonomic interest
Authors: Grant T. , Lawn R. J. , Bielig L. M.
Published: August 2003

Variation among 79 accessions of Vigna vexillata was evaluated for a range of traits of potential agronomic, taxonomic, or adaptive significance, using potted plants grown in the glasshouse over summer. There was significant variation among accessions for all of the traits evaluated except for tuber morphology. The nature and extent of variation are likely to be of agronomic interest in a plant improvement context. Variation among accessions for quantitatively inherited traits relating to phenology, biomass accumulation (vegetative growth, seeds, and tubers), and pod and seed traits was, in most instances, normally distributed, with no evidence of large discontinuities in response. There was evidence of photoperiodic adaptation among accessions from different latitudes and some interrelations between quantitative traits, for which there were usually plausible physiological explanations. Among the several qualitative traits evaluated, there was evidence of minor linkages between some alleles. There was no evidence of major discontinuities in the observed variation, and no evidence of aggregations of traits into distinctive or geographically discrete morphotypes. It is concluded that V. vexillata is relatively homogeneous across the wide geographical range over which it occurs within Australia.
Impact of legume 'break' crops on the residual amount and distribution of soil mineral nitrogen
Authors: Evans J. , Scott G. , Lemerle D. , Kaiser A. , Orchard B. , Murray G. M. , Armstrong E. L.
Published: August 2003

Important factors in the successful uptake of grain legumes by cereal growers have been their capacity to increase soil N and control cereal disease, as these have underpinned high yields in following wheat crops. However, alternative 1-year legume crops are required to introduce additional biodiversity and management flexibility for cereal growers. The effects on soil mineral N and potential contribution to soil total N of other legume enterprises were studied. These included vetch (Vicia bengalhensis) or clovers (mix of Trifolium alexandrinum, T.�versiculosum, T. resupinatum) managed for green manure; pea (Pisum sativum), vetch, or clovers managed for silage; and clovers managed for hay. These were compared with pea and lupin (Lupinus angustifolius) managed for grain production. Wheat was also included as a control. The legumes were grown in acidic Red Kandasol soil at Wagga Wagga in southern New South Wales, in 1996, 1997, and 1998. Mineral N was measured in the autumn or winter of seasons 1997 and 1998 respectively. Amounts of stubble residue N were measured in all seasons. The green manure crops, particularly vetch, produced more mineral N than both grain legumes. The forage conservation crops (silage or hay) produced similar amounts of mineral N to grain pea and more than grain lupin. For the grain and green manure legume crops, variation in amounts of mineral N was explained by the total N content of legume stubble residue, but for the forage conservation crops, more mineral N was measured than was predictable from stubble N. The amounts of mineral N at different soil depths differed between legume treatments and experiments (sites and years). Based only on above-ground plant N, the green manure crops contributed more to increasing total soil N than grain legumes; in turn, the grain legumes contributed more than the forage conservation crops. It was concluded that alternative annual legume enterprises to grain legumes may provide at least similar enrichment of soil mineral N early in the following season, and that all annual legume enterprises may accumulate nitrate deep in the soil profile in some seasons.
Gene action for leaf conductance in three wheat crosses
Authors: Rebetzke G. J. , Condon A. G. , Richards R. A. , Farquhar G. D.
Published: August 2003

Selection for altered stomatal conductance has potential to improve wheat grain yields in dry and well- watered environments. Yet the slow speed with which conductance is typically measured has limited studies reporting genetic parameters for leaf conductance. A viscous air-flow porometer that measures resistance to mass flow through a leaf was used to provide rapid estimates of leaf conductance. These estimates were obtained prior to anthesis on irrigated plants representing different generations of crosses between the low conductance parent, Quarrion, and 3 high conductance varieties, Hartog, Genaro 81, and Matong. Sampling for leaf conductance was done between 08 00 and 12 00 hours under cloud-free conditions. Significant (P < 0.01) genetic differences were observed between generation means for conductance measured in different crosses and on different days. Gene action was complex with both additive and non-additive (dominance and additive-based epistasis) genetic effects important for expression of leaf conductance. There was a greater reduction in leaf conductance for Quarrion and backcross-Quarrion progeny with sampling later into the day. In turn, genetic variances for leaf conductance increased with later sampling. Family-mean heritabilities varied in size (0.06–0.70), depending on cross and time of sampling. It is suggested that breeders selecting for altered leaf conductance maximise genetic gain by delaying screening of populations until later in the day, and repeat measurements across a minimum of 2 days. Large populations of inbred families should be evaluated in order to minimise confounding through dominance and increase the probability of recovering families containing desirable non-allelic gene combinations.
Tests of transmission of cynodon white leaf phytoplasma to sugarcane and maize in northern Australia
Authors: Blanche K. R. , Tran-Nguyen L. , Gibb K. S.
Published: August 2003

Cynodon white leaf disease is associated with cynodon white leaf phytoplasma in Cynodon dactylon growing in Darwin, Northern Territory. In order to effectively assess and manage the risk to agricultural crops posed by this phytoplasma, it is necessary to establish whether there is an insect species capable of transmitting it from C.�dactylon to grasses like Saccharum spp. hybrids and Zea mays. We used field and cage trials to investigate transmission of cynodon white leaf phytoplasma in these grasses. No transmission of the phytoplasma occurred in any of the trials, even to C. dactylon, the known host, and the phytoplasma did not persist in the potential leafhopper vector, Chiasmus varicolor. These results suggest that C. varicolor is not a vector of cynodon white leaf phytoplasma and that some requirement for successful transmission was not met in our field trials. We do not have sufficient information to determine whether transmission to Saccharum spp. hybrids or Z. mays is possible. Our study demonstrates the techniques that can be applied to this problem and provides a starting point for further investigation using different transmission conditions and insect species.
Age, sex, and weight at weaning influence organ weight and gastrointestinal development of weanling pigs
Authors: Pluske J. R. , Kerton D. K. , Cranwell P. D. , Campbell R. G. , Mullan B. P. , King R. H. , Power G. N. , Pierzynowski S. G. , Westrom B. , Rippe C. , Peulen O. , Dunshea F. R.
Published: August 2003

The present study was designed to determine the interrelationships between sex, weaning age, and weaning weight on aspects of physiological and gastrointestinal development in pigs. Forty-eight Large White × Landrace pigs were used in a factorial arrangement with the respective factors being: age at weaning (14 or 28 days), weight at weaning (heavy or light), sex (boar or gilt), and time after weaning (1, 7, and 14 days). At weaning, 48 pigs were removed from the sow: 16 pigs were then fasted for 24 h before euthanasia for determination of organ weights, gut histology, and enzymology, and 32 pigs were offered a high quality pelleted weaner diet ad libitum for subsequent assessment of organ weights, histology, and enzymology at 7 and 14 d after weaning. On Day 6 and 13 after weaning, 2 pigs from each group had their feed removed, and 24 h later were euthanased and similar measurements were taken. In general, the data highlighted the overall gastrointestinal underdevelopment of pigs weaned at 2 weeks of age and of pigs weaned light-for-age at either 2 or 4 weeks. Heavier body organs, gastrointestinal organs, and accessory digestive organs observed after weaning, except for the spleen, presumably reflected the increase in substrates available for cellular growth as feed intake increased after weaning, and the development of organs required to process this feed. Interestingly, the relative weights (% of liveweight) of the stomach and small intestine and, to a lesser extent, the caecum and colon, were greater in the light, 14-day-old weaned pigs, but these differences diminished with increasing time after weaning. Consistent effects due to age, weight, and sex were not observed for villous height and crypt depth, or for the specific activities of the brush-border and pancreatic enzymes measured. However, increases (P < 0.001) in the activities of maltase (P�<�0.001), glucoamylase (P < 0.001), and sucrase (P = 0.020) (all expressed per gram of mucosa), and that of trypsin (per gram of pancreas), occurred by 14 days after weaning. This most likely reflected the inducible nature of these enzymes in response to the increasing intake of substrates provided in the diet. In contrast, the specific activity of lactase declined (P = 0.012) in the first 14 days after weaning. These data suggest that pigs weaned at 2 weeks of age and pigs weaned light-for-age at either 2 or 4 weeks have a less developed gastrointestinal tract, and that its development after weaning might proceed differently to that of pigs weaned older and heavier.
Utilisation of wild Cicer in chickpea improvement — progress, constraints, and prospects
Authors: Croser J. S. , Ahmad F. , Clarke H. J. , Siddique K. H. M.
Published: August 2003

Efforts to improve the yield and quality of cultivated chickpea (Cicer arietinum L.) are constrained by a low level of intraspecific genetic diversity. Increased genetic diversity can be achieved via the hybridisation of the cultivated species with the unimproved 'wild' relatives from within the 43 species of the Cicer genus. To date, the 8 species sharing an annual growth habit and chromosome number with C. arietinum have been the primary focus of screening and introgression efforts. Screening of these species has uncovered morphological characteristics and resistance to a number of abiotic and biotic stresses that are of potential value to chickpea improvement programs. Detailed analysis of protein and DNA, karyotyping, and crossability studies have begun to elucidate the relationships between the annual Cicer species. In comparison, perennial species have received little attention due to difficulties in collection, propagation, and evaluation. This review discusses the progress towards an understanding of genetic relationships between the Cicer species, and the introgression of genes from the wild Cicer species into the cultivated species.
Genetic shifts in Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) over a year in the Dawson/Callide Valleys
Authors: Scott K. D. , Wilkinson K. S. , Merritt M. A. , Scott L. J. , Lange C. L. , Schutze M. K. , Kent J. K. , Merritt D. J. , Grundy P. R. , Graham G. C.
Published: August 2003

Microsatellites were used to analyse 68 collections of Helicoverpa armigera in the Dawson/Callide Valleys in central Queensland. The study aimed to evaluate the genetic structure in this region over a 12-month period (September 2000–August 2001). The results detected genetic shifts in H. armigera collections, with genetic changes occurring month by month. Collections in any month were genetically distant from the preceding month's collections. There was no observed difference between collections of H. armigera from the Biloela region and those found in the Theodore region of central Queensland. The data support the current area-wide management strategies for H. armigera by reinforcing the importance and contribution of local management practices. The study also indicates a need for the continuation of regional or Australia-wide approaches to management of the low levels of immigration that are occurring, and for future high pest pressure years.
Mating trials and genetic study of virulence in Ascochyta lentis to the lentil cultivar 'Northfield'
Authors: Skiba Beata , Pang Edwin C. K.
Published: August 2003

Ten isolates of Ascochyta lentis derived from a single conidiospore were crossed with each other in order to induce the teleomorph Didymella lentis. Mature pseudothecia and viable ascospores were produced from crosses between compatible mating types. Isolates AL27 and AL36 were determined to be MAT1-1, and isolates AL4, AL41, and USA4 to be MAT1-2. This study identified isolate RB6 to be MAT1-1, not MAT1-2 as previously reported. The inheritance of virulence in A. lentis to the lentil cultivar Northfield was studied by crossing a Northfield-attacking isolate (AL4) with an avirulent isolate (AL36). The F1 progeny segregated in a 3:1 ratio for high virulence/low virulence, suggesting that virulence of A. lentis to Northfield may be controlled by 2 independently segregating genes, operating in mutual epistasis.
Evaluating physicochemical constraints of Calcarosols on wheat yield in the Victorian southern Mallee
Authors: Nuttall J. G. , Armstrong R. D. , Connor D. J.
Published: August 2003

Soil salinity, sodicity, and high extractable boron (B) are thought to reduce wheat yields on alkaline soils of south-eastern Australia; however, little quantitative information on yield penalties to edaphic constraints is available. The relationships between wheat yield of a B-tolerant cultivar and soil physicochemical conditions in the Victorian Mallee were explored using ridge regression analysis, using natural variation in the field. Wheat yields in the survey ranged from 1.3 to 6.1 Mg/ha, with low yields attributed to inadequate soil water supply during pre-anthesis growth. Crop sequences, fallow–wheat, and pulse–wheat left greatest soil water prior to sowing of the wheat crop, and lucerne–wheat the least. A descriptive model explained 54% of variation in wheat yield, with rainfall around anthesis, available soil water in the 0.10–0.40 m layer, nitrate in the 0–0.10 m layer at sowing and salinity, and sodicity in the 0.60–1.00 m layers being important factors. Subsoil salinity (ECe) and sodicity (ESP) appear to be effective surrogates for estimating the likelihood of water extraction in the deep subsoil. The analyses suggest that subsoils need to have an ECe <8 dS/m and ESP < 19% for crops to make use of water deep in the profile. Although soluble B ranged from 2 to 52 mg/kg in the 0.60–1.00 m layer of the alkaline soils considered, B appeared to have little correlation with root growth, water extraction, or yield of wheat, which has been attributed to B-tolerance of the cultivar tested and/or the overbearing effect of high Na+ in these soils.
Lifetime and post-weaning determinants of performance indices of pigs
Authors: Dunshea F. R. , Kerton D. K. , Cranwell P. D. , Campbell R. G. , Mullan B. P. , King R. H. , Power G. N. , Pluske J. R.
Published: August 2003

The present study was designed to determine the interrelationships between sex, weaning age, and weaning weight on subsequent growth performance. Ninety-six Large White × Landrace pigs were used in a 2 × 2 × 2 factorial experiment with the respective factors being: age at weaning (14 or 28 days), weight at weaning (heavy or light), and sex (boar or gilt). Eighty pigs were offered a high quality pelleted weaner diet ad libitum while the remaining 16 pigs (2 pigs from each treatment group) were removed from the sow and fasted for 24 h before being euthanased for determination of gut histology and enzymology. The remaining pigs were weaned into individual pens and given an ad libitum diet containing 15.5 MJ DE/kg and 0.95 g available lysine/MJ DE. On Day 6 and 13 after weaning, 2 pigs from each group at each time had their feed removed and, 24 h later, were euthanased. From 3 weeks post-weaning, the remaining pigs were group-penned with contemporary pigs and fed commercial rations until slaughter at 23 weeks of age. In the first week after weaning, the heavy pigs and those weaned at 28 days ate more feed and grew faster, and gilts ate more and grew faster than boars over the same time. Pigs that were heavier at weaning were also heavier at every subsequent age. At slaughter, heavy boars weighed more than heavy gilts (110.5 v. 103.7 kg, P = 0.027), whereas this was not the case for light boars and gilts (94.1 v. 94.4 kg, P = 0.96). Whereas there were no effects of sex or weight at weaning on P2 backfat depth, pigs weaned at 14 days had more backfat at 23 weeks than pigs weaned at 28 days (13.1 v. 10.9 mm, P = 0.009). In conclusion, these data clearly indicate that the greatest determinants of immediate post-weaning performance under the present conditions were the age and weight of the pigs at weaning. However, the key determinant of lifetime growth rate appeared to be weight of pigs at weaning or, by inference, birth. Although age at weaning had no effect on lifetime growth rate, early-weaned pigs were fatter at slaughter.
The growth performance and carcass attributes of Merino and Poll Dorset × Merino lambs fed rumen-protected methionine (Smartamine™-M)
Authors: Wiese S. C. , White C. L. , Masters D. G. , Milton J. T. B. , Davidson R. H.
Published: August 2003

This study investigated the effect of 5 levels of rumen-protected methionine (0, 1, 2, 3, or 5 g/head.day) on growth rate, feed conversion efficiency, carcass composition, and wool growth in lambs fed a production diet ad libitum. Merino and Poll Dorset × Merino (crossbred) wether lambs (120 of each genotype) were housed in group pens each of 6 sheep. After a 1-week adjustment period, all lambs were fed a pelleted diet of lupins, cereal grain, and hay ad libitum. Rumen-protected methionine was added to the diets in the form of Smartamine™-M. The crossbred lambs were slaughtered after 28 days on the treatment diet and the Merino lambs after 42 days.Increasing the level of methionine supplementation did not lead to an increase in growth rate, daily feed intake, feed conversion efficiency, wool growth, skin thickness, or final liveweight and condition score. The Merino lambs had a lower growth rate, thinner skin, faster rate of wool growth, and were less efficient at converting feed into liveweight gain than the crossbred lambs (P < 0.05). There was no interaction between breed and methionine treatment.Increasing the level of methionine treatment also did not improve hot carcass weight, dressing percentage, tissue depth over the rib, longissimus dorsi (LD) cross-sectional area, meat pH, or meat colour. The only beneficial effect of methionine supplementation on carcass attributes was a decline in fat depth over the deepest part of the LD as methionine level increased (P < 0.05).There were no differences in tenderness, juiciness, or flavour intensity between the breeds or as a main effect with methionine supplementation. However, there was an interaction between breed and methionine for flavour intensity, such that methionine supplementation reduced the flavour intensity of Merino meat but not that of the crossbred meat (P < 0.05).This work suggests that there are unlikely to be production gains in terms of liveweight gain, feed conversion efficiency, or wool growth in supplementing lambs with protected methionine if they are being fed a high performance diet ad libitum. However, there were 2 benefits that may have scope for further investigation. The first was a reduction in fat cover over the loin as the level of methionine supplementation increased. The second was a reduction in the intensity of flavour found in Merino lamb when the lambs were supplemented with methionine. The study also provided some useful guidelines for the differences in growth and carcass characteristics between Merino and crossbred lambs when they are finished under identical conditions to an even fat cover, and demonstrated that Merino lambs can produce carcasses of very acceptable eating quality when well finished.
Plant reserves of perennial grasses subjected to drought and defoliation stresses on the Northern Tablelands of New South Wales, Australia
Authors: Boschma S. P. , Scott J. M. , Hill M. J. , King J. R. , Lutton J. J.
Published: August 2003

The effects of defoliation intensity and drought severity on levels of water-soluble carbohydrate (WSC), fructan, and etiolated regrowth of 6 important perennial grasses were investigated. The experiment was conducted under a rain-out shelter at Armidale, NSW, Australia, using 6 perennial grass species (Phalaris aquatica cv. Sirosa, Festuca arundinacea cv. Demeter, Dactylis glomerata cv. Porto, Lolium perenne cv. Victorian, Microlaena stipoides cv. Shannon, and Austrodanthonia richardsonii cv. Taranna) subjected to 3 moisture regimes (non-stress moisture, and moderate and severe drought) and 2 defoliation intensities (moderate and severe) over 2 seasonal sequences (spring–summer and summer–autumn).The range in WSC, fructan, and etiolated regrowth of the species varied, with Festuca and Lolium having the highest WSC and fructan concentrations. Austrodanthonia had the lowest WSC concentration of the species. Unlike the introduced species, the natives did not store fructans. The species varied in their response to the treatments imposed. Festuca and Phalaris had the highest etiolated regrowth and showed the greatest effect of defoliation intensity. Etiolated regrowth appeared to be a sensitive measure of plant status, showing the fragile nature of some of the species.The effect of defoliation intensity and drought varied with season. Defoliation intensity had little effect on carbohydrate reserves of all species, except Festuca, during summer of the spring–summer experimental season. During the summer–autumn experimental season, severe defoliation reduced the rate of accumulation during the period December–April. Drought affected carbohydrate accumulation and utilisation. Carbohydrates that had been accumulated at the end of spring of the spring–summer experimental season in plants affected by drought were utilised during summer. However, if drought commenced in summer, carbohydrate accumulation continued for 120 days in all species studied, and 180 days in Lolium and Phalaris.Autumn appeared to be a period when plant reserves were particularly susceptible to stress. The importance of WSC, fructans, and etiolated regrowth as measures of plant reserves, and their role in persistence were discussed.
Long-term effects of multiple applications of nitrogen fertiliser on grazed dryland perennial ryegrass/white clover dairy pastures in south-west Victoria. 1. Nitrogen fixation by white clover
Authors: McKenzie F. R. , Jacobs J. L. , Riffkin P. , Kearney G. , McCaskill M.
Published: August 2003

A 3-year experiment determined the impact of multiple applications of different rates of nitrogen (N) fertiliser, applied over autumn and winter in 1997, 1998, and 1999, on N2 fixation in grazed dryland perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) dairy pastures. Four treatments replicated 3 times in a randomised block design comprised: 0 N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D). Urea (46% N) was the N source and applications were from autumn to late winter. 15N abundance methods, based on herbage samples, were used to estimate N2 fixation. Percentage N derived from the atmosphere (%Ndfa) through white clover N2 fixation decreased as the rate of N fertiliser application increased during 1997, but remained unaffected by treatment during 1998 and 1999. Slight decreases in %Ndfa, associated with an increase in soil nitrate, were offset by the positive association between clover dry matter (DM) and soil ammonium. The amount of N2 fixed by white clover decreased from 43 kg N/ha.year (A) to 23 kg N/ha.year (C) during 1997. The amount of N2 fixed by white clover during 1998 and 1999, however, was unaffected by increasing rates of N fertiliser application and averaged 17 and 12 kg N/ha.year in 1998 and 1999, respectively. White clover sward composition (percentage of DM) was unaffected by the rate of N fertiliser application. The average white clover composition across treatments declined from 23% DM in 1997 to 12% DM in 1999. It is concluded that the DM yield production of dryland perennial ryegrass/white clover dairy pastures is likely to be restricted by available soil N, as the amount of N2 fixed annually by clover is low (approx. 20 kg N/ha.year). There is, therefore, scope to supplement pasture N nutritional requirements with fertiliser N. Further, application of N fertiliser may restrict the ability of white clover to fix N2; however, under the grazing management adopted, N fertiliser had no effect on the percentage of white clover.
Long-term effects of multiple applications of nitrogen fertiliser on grazed dryland perennial ryegrass/white clover dairy pastures in south-west Victoria. 2. Growth rates, dry matter consumed, and nitrogen response efficiencies
Authors: McKenzie F. R. , Jacobs J. L. , Kearney G.
Published: August 2003

A 3-year grazing experiment undertaken on a commercial dairy farm in south-west Victoria ascertained the effects of multiple applications of different rates of nitrogen (N) fertiliser over autumn and winter on pasture growth rates, dry matter (DM) consumed, and N fertiliser response efficiencies. Four treatments, replicated 3 times in a randomised block design, comprised: zero N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D), with N applied as urea (46% N).Treatments B, C, and D increased pasture growth rates relative to Treatment A, with Treatments C and D having the greatest affect. Treatments B, C, and D also increased pasture DM yield, with Treatment D having the greatest effect. Total pasture DM consumed in 1997 was 7.1, 7.9, 8.2, and 8.9 t DM/ha for A, B, C, and D, respectively. For 1998, the values were 5.4, 6.5, 7.2, and 8.7; and in 1999 5.7, 6.6, 6.9, and 7.7 t DM/ha. During 1997, N response efficiencies were 11, 7, and 8 kg DM/kg N for treatments B, C, and D, respectively. Based on a cost of AU$400/t urea (including freight, handling, and spreading), Treatment B was the most economical, costing 8 cents/kg additional pasture DM produced. Nitrogen application resulted in response efficiencies of 14, 12, and 15 kg DM/kgN in 1998 and 13, 8, and 9 kg DM/kg N in 1999 for Treatments B, C, and D, respectively. In 1998 the most economical application was Treatment D, costing 6 cents/kg additional pasture DM produced, whilst in 1999 Treatment B was most economical costing 7 cents/kg DM for additional pasture. The apparent recovery of applied N fertiliser by the pasture was calculated and found to fall within the range reported in the literature. Apparent recoveries estimated during 1997, 1998, and 1999, respectively, were Treatment B: 62, 78, and 70%; Treatment C: 50, 69, and 45%; and for Treatment D: 45, 82, and 51%.It is concluded that, for the range of N fertiliser rates tested, N fertiliser is a cost-effective option for the production of extra pasture DM during autumn and winter on grazed perennial ryegrass dairy pastures in south-west Victoria.
Long-term effects of multiple applications of nitrogen fertiliser on grazed dryland perennial ryegrass/white clover dairy pastures in south-west Victoria. 3. Botanical composition, nutritive characteristics, mineral content, and nutrient selection
Authors: McKenzie F. R. , Jacobs J. L. , Kearney G.
Published: August 2003

A grazing experiment was undertaken on a commercial dairy farm in south-west Victoria over a 3-year period to study the effects of multiple applications of different rates of nitrogen (N) fertiliser over autumn and winter on dairy pasture species composition, nutrient characteristics, mineral content, and nutrient selection. Four treatments, replicated 3 times in a randomised block design, comprised: zero N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D).Increasing rates of N fertiliser generally elevated whole sward metabolisable energy (ME) content. The effect of N fertiliser on whole sward ME content was evident through to the end of sampling each year (2–3 months after the last N application). Increasing rates of N fertiliser consistently elevated whole sward crude protein (CP) content. The effect of N fertiliser on whole sward CP content was evident through to the end of sampling each year (2–3 months after the last N application). For each year there was a slight decrease in CP, with Treatments C and D decreasing at a greater rate than treatments A and B. Increasing rates of N fertiliser generally depressed whole sward neutral detergent fibre (NDF) content. The effect of N fertiliser on whole sward NDF content was evident through to the end of sampling each year (2–3 months after the last N application). For each year there was a slight increase in NDF, with Treatments C and D having a lower increase in NDF over time than Treatment A. Nitrogen fertiliser had no effect on whole sward water soluble carbohydrate content.There was no consistent effect of N fertiliser on whole sward pasture mineral content during the growth season (June–December), with mean annual levels of P, K, S, Na, Ca, and Mg satisfying the nutritional requirements of high producing dairy cows and the growth requirements of both perennial ryegrass and white clover.Although N fertiliser had no influence on the concentration of nutrients consumed by grazing dairy cows, the mean annual range in selection differentials for the 3 years for ME (1.06–1.11) and CP (1.18–1.32) concentrations consumed was higher and the NDF (0.85–0.91) lower than those of the pasture.Each year there was an increase in perennial ryegrass, with Treatments B and C having a higher overall ryegrass presence compared with Treatment A. Nitrogen fertiliser had no effect on white clover, other grasses, weeds, or dead fractions.
Agronomic potential of genetically diverse narrow-leafed lupins (Lupinus angustifolius L.) with restricted branching
Authors: Galwey N. W. , Adhikari K. , Dracup M. , Thomson R.
Published: August 2003

The indeterminate growth habit of narrow-leafed lupin appears to cause a suboptimal pattern of grain filling in the Mediterranean-type environment of south-western Australia. Development of cultivars with genetically restricted branching (RB) has been proposed to overcome the problem. However, restriction of branching causes profound phenological and architectural changes, and it may be necessary to compensate for these by incorporating RB into a genetic background that confers high shoot mass. In order to make a robust assessment of the value of RB in a range of backgrounds, the trait was incorporated from 5 donor parents into the genetic background of 10 recurrent parents by 2 rounds of back-crossing followed by self-fertilisation of the progeny for 4 generations to produce BC2S4 lines. Thirty-two of these lines were obtained with highly RB or mildly RB, a range of flowering times from 68 to 118 days after sowing, and 16–34 leaf nodes on the main stem. They were tested with their parents in replicated field trials at 3 sites in Western Australia at latitudes from 28°S to 33°S. The RB genotypes generally gave higher grain yield than the normal-branching genotypes at the high-latitude, high-rainfall, long growing season, high shoot mass producing site of Esperance, and the 2 types gave approximately equal yield in the low-latitude, low-rainfall, short-season, low shoot mass site of Mullewa. Only at the intermediate site of Wongan Hills did the normal-branching genotypes have a clear advantage. RB genotypes had higher harvest index than corresponding normal-branching genotypes, particularly at Esperance, and tended to produce more pods but slightly fewer seeds per pod and lighter seeds. There was no consistent difference in performance between highly and mildly RB genotypes, contrary to an expectation that the highly RB type would produce insufficient shoot mass. There was a tentative indication that, within RB lines, a large number of leaf nodes on the main stem conferred more reliably high grain yield in the environments of Esperance and Wongan Hills. Overall, these results provide ample justification for the development and further evaluation of RB cultivars. However, this conclusion comes with 2�caveats: that a different background development pattern should be adopted to that used in normal branching lupins, and that RB cultivars should be evaluated in the target environments where the character confers an advantage.
Validation of the n-alkane technique to estimate intake, digestibility, and diet composition in sheep consuming mixed grain:roughage diets
Authors: Valiente O. L. , Delgado P. , Vega A. de , Guada J. A.
Published: August 2003

The usefulness of the n-alkane technique to estimate intake, digestibility, and diet composition in sheep fed mixed diets was tested in an experiment with 16 ewes consuming 4 different proportions of barley grain and straw ranging from 15:85 to 60:40. Two cases were considered: (1) straw as one component or (2) straw separated into leaves and stems. The relationship between estimated (Y) and observed (X) proportion of grain in the diet was highly significant (1: Y = 0.2355 + 0.9945X, r2 = 0.9999; 2: Y = –2.472 + 1.0063X, r2 = 0.9999). Actual intake was overestimated in (1) by 3.43–12.40%, the largest discrepancies corresponding to the lowest proportions of grain. In (2) actual intake was either overestimated (2.69%) or underestimated (5.38–6.85%), without a clear effect of the diet. A similar pattern was observed for digestibility, which was overestimated in (1) by 1.65–9.59% and overestimated, (by 2.07%) or underestimated (by 3.80–4.62%) in (2). Due to the small discrepancies between observed and estimated values, it may be concluded that the n-alkane technique might be a valid method for estimating intake, digestibility, and diet composition in sheep consuming mixed diets, for the two latter provided that faecal recovery of individual n-alkanes is calculated with enough accuracy.
Impact of legume 'break' crops on the yield and grain quality of wheat and relationship with soil mineral N and crop N content
Authors: Evans J. , Scott G. , Lemerle D. , Kaiser A. , Orchard B. , Murray G. M. , Armstrong E. L.
Published: August 2003

The effect of annual 'break' crops on the yield and protein content of wheat was investigated over 3 seasons on a Red Kandasol on the south-western slopes of New South Wales. The 'break' crops included lupin and pea grown for grain, pea and vetch managed for silage, clovers managed for silage or hay, and vetch and clovers managed for green manuring. Wheat was sown for 2 years following the legume year, or canola and wheat followed the legumes. Averaged over 3 experiments the yields of first crop wheat following pea or vetch silage crops were comparable with those after grain pea. Yields following clover forage conservation crops or green manures exceeded those after grain pea by at least 0.41 t/ha; average yield increase after clover green manure was 0.93 t/ha. In one experiment, yields of second crop wheat were greater, by up to 0.37 t/ha, after forage conservation or green manure legume 'breaks' than after grain legumes. In 2 experiments, second crop wheat yields were greater after a first crop of canola than a first crop of wheat. Compared with continuous wheat yield, aggregate mean wheat yield increases were 3.5–4 t/ha following grain legumes, pea, and vetch silage crops, but 5.3–6.3 t/ha following clover forage conservation and green manure crops. However, the relative effects of legume treatments on wheat yield were significantly seasonally dependent. Yield and grain protein variation in wheat after legumes was significantly correlated with variation in mineral N at wheat establishment. However, in one experiment, yield was correlated only with variation in mineral N below the 20-cm soil depth, whereas protein was correlated only with variation in mineral N above the 20 cm soil depth. Yield increases in first crop wheat did not occur at the expense of grain protein.
Mapping of a QTL contributing to cereal cyst nematode tolerance and resistance in wheat
Authors: Williams K. J. , Lewis J. G. , Bogacki P. , Pallotta M. A. , Willsmore K. L. , Kuchel H. , Wallwork H.
Published: August 2003

Cereal cyst nematode (CCN; Heterodera avenae Woll.) is a root pathogen of cereals that can cause severe yield losses in intolerant wheat cultivars. Tolerance to CCN, measured as early vigour in CCN-infested plots, was mapped in a Trident/Molineux doubled-haploid (DH) population. A locus accounting for a significant proportion of the tolerance to CCN was mapped to chromosome 6B of Molineux by association with RFLP loci Xcdo347-6B and Xbcd1 and also by nullisomic/tetrasomic substitution line analysis, and has been designated Cre8. The linkage of CCN tolerance with Xcdo347-6B was validated using a Barunga/Suneca DH population. The Cre8 locus also contributed to CCN resistance in the Trident/Molineux population. The RFLP locus Xbcd175, which is diagnostic for the Aegilops ventricosa segment VPM1 of Trident, explained up to 18% of the variation for early vigour in CCN-infested soils in the Trident/Molineux population. However, the Trident/Molineux population also segregated for early vigour in the absence of CCN, with Xbcd175 explaining up to 7% of the variation for this trait. The VPM1 segment of Trident therefore provides early vigour that may contribute to CCN tolerance in this cultivar.
Influence of sire by year interactions on the direct-maternal genetic correlation for weaning weight of Western Australian Merino sheep
Authors: Konstantinov K. V. , Brien F. D.
Published: August 2003

The relationship between the direct-maternal genetic (co)variance σam and sire by year (SY) interactions for weaning weight in Merino sheep was examined through simulation and real data analyses. Weaning weight was simulated using models containing interaction and σam = 0 (S1), interaction and σam < 0 (S2), interaction and σam >�0 (S3), and without interaction and σam < 0 (S4). When S1 data were analysed ignoring interaction, a negative (co)variance was observed and direct and maternal variances were inflated. Analysis of S2 data ignoring σam resulted in deflated direct and maternal variances, inflated residual and interaction variances, and no change for the permanent environmental component. Ignoring the interaction effect in S3 data resulted again in a negative (co)variance component and highly biased genetic parameters. On application to weaning weight of Merino sheep, the model ignoring SY resulted in a direct-maternal genetic correlation of –0.43. The model using both (co)variance and interaction effects fit the data better (P < 0.001). The interaction variance represented 9.2% of the phenotypic variance but explained 86% of the (co)variance between direct and maternal genetic effects estimated ignoring SY.�A small (–0.096) but still negative estimate of the genetic correlation was obtained. The implication of these findings in the context of Central Test Sire Evaluation and Maternal Sire Central Progeny Test Schemes is discussed.
Supplementation of a tropical grass diet with forage legumes and Sapindus saponaria fruits: effects on in vitro ruminal nitrogen turnover and methanogenesis
Authors: Hess H. D. , Monsalve L. M. , Lascano C. E. , Carulla J. E. , Díaz T. E. , Kreuzer M.
Published: August 2003

In two in vitro experiments with the RUSITEC-apparatus, Brachiaria dictyoneura was tested alone and with legumes at dietary proportions of 1/3, 2/3, or 3/3 of Arachis pintoi (Expt 1) and 1/3 of Arachis pintoi, Cratylia argentea, or Calliandra calothyrsus (Expt 2). In Expt 2, all diets were evaluated with and without 80 mg/g diet of Sapindus saponaria fruits. In Expt 1, the stepwise replacement of the grass by A. pintoi curvi-linearly increased rumen fluid concentrations of ammonia, volatile fatty acids, bacteria, and protozoa. Methane release rates were 1.7, 7.3, 8.8, and 9.0�mmol/day. With increasing legume proportion, more organic matter and protein were degraded, the latter being only partially recovered as ammonia. In Expt 2, 1/3 of A. pintoi basically had the same effects as in Expt 1. Cratylia argentea was less effective in modifying the fermentation pattern. In association with a higher nutrient degradation and rumen ammonia concentration, C. argentea and A. pintoi increased methane release to about 3- and 4-fold levels. Calliandra calothyrsus reduced nutrient degradation and methane release per gram of organic matter degraded. Tannins, predominant in C. calothyrsus, might have affected methanogenesis. Sapindus saponaria reduced methanogenesis by 11% on average in grass-alone and legume-supplemented diets.
Nutritional manipulation increases intramuscular fat levels in the Longissimus muscle of female finisher pigs
Authors: D'Souza D. N. , Pethick D. W. , Dunshea F. R. , Pluske J. R. , Mullan B. P.
Published: August 2003

Fifty crossbred (Large White × Landrace × Duroc) female finisher pigs were used to determine the effect of nutritional manipulations on intramuscular fat deposition. The main nutritional treatments were (i) Control (pigs fed a commercial grower diet), (ii) –15% P : DE (pigs fed a 15% reduced protein : digestible energy diet during the grower phase), (iii) –30% P : DE (pigs fed a 30% reduced P : DE diet during the grower phase), (iv) +6% Fat (pigs fed diet supplemented with 6% additional fat during the grower phase), and (v) –Vit A (pigs fed a control diet with no supplemented Vit A in the mineral vitamin premix during the grower and finisher phase). Pigs fed the 30% reduced P : DE diet had an inferior feed to liveweight gain (feed conversion ratio, FCR) for the combined grower and finisher growth period (P = 0.036) compared with the other dietary treatments. There were no significant differences in average daily gain (ADG) or voluntary feed intake (VFI) for the grower, finisher, and the combined grower and finisher phases, or liveweight at slaughter between the dietary treatments. Pigs fed the 15% (1.9%) and 30% (2.7%) reduced P : DE diet, and the Vit A-restricted diet (2.0%), had significantly higher intramuscular fat (IMF) levels compared with pigs fed the other diets. Pigs fed the control diet had higher (P = 0.002) carcass dressing percentage compared with pigs fed the other diets. There were no significant dietary effects on total fat tissue (P�=�0.661), total lean muscle tissue (P = 0.637), and total bone mineral (P = 0.367) content. In conclusion, these data indicate that feeding pigs grower diets with 15% and 30% reduced P : DE, and grower and finisher diets restricted in Vit A, improved the IMF levels in the Longissimus muscle. The increase in IMF levels in pigs fed the 15% reduced P : DE diet, and grower and finisher diets restricted in Vit A, improved the IMF levels without having a detrimental effect on growth performance and carcass quality.
Genetics of starch granule size distribution in tetraploid and hexaploid wheats
Authors: Stoddard F. L.
Published: August 2003

Wheat endosperm starch is deposited in large, A-type granules and smaller B-type and C-type granules. The quantitative genetics of starch granule size distribution was investigated in 2 ways. Complete diallel crosses, with 5 parents each, were prepared in tetraploid wheat, Triticum turgidum, and hexaploid wheat, Triticum aestivum. Parent and F1 plants were grown in controlled environment growth chambers with 18�C days and 13�C nights to provide parent and F2 grains from uniform conditions. In the same conditions, the basic generations of parent, F1, F2, and backcross of 6 other individual crosses were grown and F1 and backcross grains were freshly generated on these plants. Starch granule size distribution was determined in parent and F2 grains in the diallels and all possible generations in the other crosses. Granules of <10 μm diameter were considered 'B granules' (thus including C granules), and B-granule content was expressed as a percentage of total starch volume. The modal A-granule diameter was also determined.B-granule content varied widely in both species, whereas modal A-granule diameter was much more variable in tetraploids than in hexaploids. Additive gene action was more important than dominance in determining B-granule content in both species and A-granule diameter in tetraploids, whereas dominance was more important for A-granule diameter in hexaploids. Dominance acted to increase or to decrease B-granule content, depending on the cross. According to variance–covariance analysis, the line with the most dominant alleles in the hexaploids was the one lowest in B granules, but in the tetraploids it was the one highest in B granules. Digenic interactions affected B-granule content and A-granule diameter in all of the analyses of the basic generations, and nucleocytoplasmic interactions affected these traits in most of the crosses. Diallel analyses of the F2 generations, in contrast, showed a limited importance of epistasis. Cytoplasmic effects made small but significant contributions to the variation in B-granule content in some of the crosses. Variation in B-granule content and A-granule diameter appeared to be affected by different gene actions and were therefore likely to be susceptible to independent manipulations in a breeding program.