bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of fleece wettability in sheep and its relationship to susceptibility to fleece rot and blowfly strike
Authors: Pascoe L
Published: November 2004

Fleece wettability in sheep is a character believed to be related to susceptibility to fleece rot and blowfly strike. The present study was undertaken to investigate that hypothesis and to assess wettability as a possible character for a selection program. Wool samples were taken from two flocks which had been subject to selection for wool quality and resistance to fleece rot and a third flock which was unselected. The wettabilities of about 800 samples were determined. The results were found to be repeatable and the technique was capable of distinguishing between sheep. Some problems of measurement are discussed. In the one flock with a significant incidence of fleece rot, susceptibility to fleece rot was found to be associated with higher wettabilities. The mean wettability and the variance were found to be significantly higher in the unselected flock than in the two selected flocks. The heritability of wettability was estimated in the two selected flocks and was found to be low. It is argued that there is likely to be more additive genetic variance in the unselected flock and that the observed difference in wettability was due to a correlated response to selection for resistance to fleece rot. It is considered that further work on the heritability of wettability and its genetic correlations with other characters of economic importance could be fruitful.
Genetic studies of South Australian Merino sheep. 4. Genetic, phenotypic and environmental correlations between various wool and body traits
Authors: Gregory IP
Published: November 2004

Genetic, phenotypic and environmental correlations were estimated between 23 quantitative and qualitative wool and body traits of South Australian Merino sheep. Clean fleece weight was significantly correlated genetically with greasy fleece weight (0.62), yield (0.47), staple length (0.41), crimps per inch (-0.34), secondary/primary follicle ratio (0.37) and skin thickness (0.39). No significant half-sib genetic correlation was found between clean fleece weight and fibre diameter and the dam-offspring correlation was quite low, although significant (0.16, P < 0.05). This indicates that selection for clean fleece weight should not lead to any great increase in fibre diameter. Skin thickness is discussed as a possible early indicator of clean fleece weight.
Liveweight changes and carcass measurements in buffalo (Bubalis bubalis) and Brahman × Northern Territory Shorthorn (Bos indicu × B. taurus) steers up to 4 years of age grazing on improved pastures
Authors: Robertson JA , Ford BD , Morris CA
Published: November 2004

Ten buffaloes and eight Brahman x Northern Territory Shorthorn steers, originating from a single Northern Territory herd and grazing improved pastures near Darwin, were compared for growth up to 51 months of age and for carcass attributes. After the weaning weight, eight liveweights per animal were strategically chosen at the beginning and end of pasture seasons, the data being adjusted for known fixed effects. The buffaloes were significantly (P < 0.05) heavier at weaning (+ 17% or +23 kg) and at three of the later weights, the average difference at all the eight later weights being + 10% or +24 kg. Difference in empty liveweight and carcass weight was not significant, but the buffaloes had a significantly lower dressing percentage (-3.0%). Condition scores were taken on 24 occasions throughout the growth phase, buffaloes having significantly higher unadjusted scores on 19 occasions. At slaughter the buffaloes had a significantly greater backfat depth at the 12-13th rib (+2.3 mm). The coefficient of variation of liveweight changed little between wet and dry seasons. Older animals were heavier in spite of dry periods when the whole group lost weight. Overall mean growth rates for seven periods ranged from -0.42 to +0.58 kg/day. Variation among animals in liveweight change was important in the dry as well as in the wet seasons, with no evidence of compensatory gain.
Enzymic diagnosis of copper deficiency in subterranean clover. I. Relationship of ascorbate oxidase activity in leaves to plant copper status
Authors: Loneragan JF , Delhaize E , Webb J
Published: November 2004

Ascorbate oxidase activity in leaf blades of various ages was examined in relation to copper supply to subterranean clover cv. Seaton Park grown in the glasshouse on a copper-deficient sand. At each copper level, ascorbate oxidase activity per g fresh weight was highest in the youngest leaf blades and declined steeply with age; activity per leaf remained relatively constant with leaf age. On either basis, and in leaf blades of each age category, ascorbate oxidase activity followed copper level. The activity per young folded leaf (YFL) was chosen as the most suitable criterion for a diagnostic test of copper deficiency. Ascorbate oxidase activity per YFL correlated closely with the response to copper of the dry matter yield of plant tops. Activity per YFL also correlated closely with copper concentrations in the youngest open leaf (YOL). These correlations held for Seaton Park subterranean clover when nitrogen was supplied either as NH4NO3 or by symbiotic fixation. Ascorbate oxidase activity in YFL of Mt Barker subterranean clover grown at varying copper levels in the field also correlated closely with YOL copper concentrations in the same plants. Moreover, subterranean clover plants deficient in any one of six other nutrients (nitrogen, sulfur, phosphorus, potassium, manganese, zinc) all had ascorbate oxidase activities above the suggested critical value for adequate copper supply. It is suggested that ascorbate oxidase activity in YFL can be used as a specific and sensitive test for the copper status of subterranean clover, with activities of = 50 nmol O2/min per leaf indicating deficiency, = 100 indicating sufficiency, and 50-100 indicating a marginal copper supply.
The effects of duration, timing and chemical amelioration of short-term waterlogging during furrow irrigation of cotton in a cracking grey clay
Authors: Hodgson AS
Published: November 2004

The effects of the duration, timing and chemical amelioration of short-term waterlogging during furrow irrigation of cotton in a cracking grey clay soil were investigated at Narrabri, N.S.W. Water was run in furrows for 4, 8, 16, 32 and 64 h at each of the three crop irrigations. In other treatments, watering was extended from 4 to 16 h either at the first, second or third irrigation, to establish at which irrigation waterlogging had the most effect. Soil applications of hydrogen peroxide and foliar sprays of urea were evaluated as chemical ameliorants of short-term waterlogging. Increasing the period of inundation from 4 to 32 h reduced green bolls m-2 by 17.5 %, open bolls m-2 by 20.6 % and final lint yield by 300 kg ha-1 or 18.3 %. No further decreases were observed by increasing the period of inundation to 64 h. Extended waterlogging was equally damaging at each of the three irrigations. The rate of recovery from waterlogging to an air-filled porosity of 0.10 cm3 cm-3 in the top 20 cm of soil was highly correlated with lint yield, and was consistent with results from a previous season. Soil applications of hydrogen peroxide did not ameliorate waterlogging damage, whereas significantly higher lint yields were obtained from foliar sprays of urea applied prior to each irrigation. The results confirmed that cotton should be irrigated and thereafter drained rapidly in this soil to minimize loss of yield. This could be achieved by increasing the rate of application of irrigation water and by using shorter fields and steeper slopes. The use of chemical ameliorants requires further investigation.
Long-term availability of phosphorus from calcined rock phosphate compared with superphosphate
Authors: Bolland MDA , Bowden JW
Published: November 2004

The phosphorus supply from single dressings of three rates of superphosphate and Christmas Island C-grade ore calcined at either (a) 500�C or (b) 900�C were compared in a long-term field trial by measuring (i) bicarbonate-extractable phosphorus and (ii) dry weight of tops of a subterranean clover based pasture in spring each year. For superphosphate, the bicarbonate-extractable phosphorus decreased with time, whereas for the two calcined products, the amount of bicarbonateextractable phosphorous, although initially low, increased slightly with time. As measured by herbage yield, the effectiveness of superphosphate decreased from the first to the second year and thereafter changed little with time. The effectiveness of the two calcined products tended to increase with time. Superphosphate was much more effective than the two calcined products throughout the trial. The effectiveness of both calcined products were similar, despite the fact that the fertilizers differed in their proportions of total phosphorus which was soluble in neutral ammonium citrate. The bicarbonate soil test did not always predict the same future pasture production for the three phosphorus sources, indicating that different soil test calibration curves are needed for each source.
The effect of a common date of either anthesis or planting on the rate of development and grain yield of wheat
Authors: Woodruff DR
Published: November 2004

In field experiments in southern Queensland comparisons were made, for a given wheat genotype, of the influence on grain yield of varying the rate of development while maintaining common dates either of anthesis or of planting. Rates of development were varied by the use of extended photoperiods or of isogenic lines of Triple Dirk varying in developmental rate. Hastened development lowered spikelet numbers and total dry weight at anthesis in all the genotypes tested, under highly stressed dryland and fully irrigated conditions. The saving in water use due to fast development rate, measured as available water at anthesis, was not proportional to the difference in total dry weight. This could be due to additional effective rainfall in the longer growing season wheats, to a high rainfall event just prior to anthesis reducing differences in available soil water, or to the complete use of soil water reserves in all treatments. With a common anthesis date, the saving in water use by the quicker developing crops (i.e. later planted) did not offset their lower dry weights and spikelet numbers at anthesis, so that there was either no yield difference or a yield decline with faster development rates. Where common dates of planting were compared the faster developing treatment (i.e. earlier flowering) still showed a trend to reduction in grain number per unit area, but this was usually offset by higher kernel weights. The yield outcome in this case was dominated by the prevailing environmental conditions at the differing anthesis dates.
Effects of reduced variance due to selection in open nucleus breeding systems
Authors: Mueller JP , James JW
Published: November 2004

In the design of breeding programs the consideration of open nucleus breeding systems may result in a useful alternative. The available theory dealing with these systems assumes constant parameters, but a more exact approach would take into account the possible changes in genetic variance. Numerical evaluation of formulae allowing for loss of genetic variance due to linkage disequilibrium and increase of variance due to mixing groups with different breeding values, suggests that optimum transfer rates, as predicted from the constant parameter theory, are in close agreement with the actual values; however, genetic gain is overestimated by about 20 % in common cattle and sheep nucleus breeding schemes for traits with high heritability, but less for traits with low heritability. The advantage of opening the nucleus is approximated well by constant variance theory.
Effect of salinity level on uptake and distribution of chloride, sodium and potassium ions in citrus plants
Authors: Walker RR , Douglas TJ
Published: November 2004

Seedlings of the Citrus rootstocks Rangpur lime (Citrus reticulata var. austera hybrid?), Kharna khatta (C. karna Raf.) and Etrog citron (C. medica L.), were grown in a porous medium under glasshouse conditions and irrigated with 0, 25, 50 or 100 mM NaCl for 6 weeks. Chloride concentrations in roots of all three rootstocks were increased by salt treatment. Increasing the level of salinity from 25 to 100 mM NaCl did not increase further the chloride concentrations in roots of any rootstock, implying an upper limit to the extent of chloride loading in roots. The upper limit appeared to be similar for all rootstocks. Differences between the rootstocks were found in chloride concentrations in leaves and to a lesser extent in stems, emphasizing pronounced rootstock differences in root to shoot transport of chloride, i.e. in their ability for chloride exclusion. This ability increased in the order: Etrog citron, Kharna khatta, and Rangpur lime. Root, stem and leaf sodium concentrations increased with salt treatment, but a concurrent reduction in potassium concentrations with salt treatment occurred only in roots and stems. Shoot growth of Etrog citron and Kharna khatta plants was reduced significantly by 50 mM NaCl, but growth of Rangpur lime plants showed a marked reduction only at 100 mM NaCl. Shoot-growth and salt-induced changes in the concentrations of chloride, sodium and potassium in leaves and roots of each rootstock were unaffected by sodium to calcium ratios in the range 6.25 : 1 to 25 : 1 for plants treated with 50 mM NaCl, and in the range 12.5 : 1 to 50 : 1 for plants treated with 100 mM NaCl. Shoot growth and ion uptake patterns
A synoptic approach for crop loss assessment used to study wheat. VI. The pathogen data and their relationship to soil and cultural data
Authors: Stynes BA , Veitch LG
Published: November 2004

As a part of a general investigation of factors that affect wheat crops on Yorke Peninsula, S. Aust., pathogens were measured at 3 and 8 weeks after emergence of the crop and at anthesis. A first study for regression work showed that, except on the coronal root system at anthesis, the pathogen data were independent of the soil and cultural practice data. Further, it showed that patterning within the pathogens was quite weak and so the value of alternative representations was marginal in this situation. In a second study, significant relationships were found between logarithmically transformed pathogen data, first within the pathogens between sampling times and root systems, and second between the pathogens and the soil and cultural practice data. The former relationships were mostly of the expected type in that high levels of a particular pathogen tended to persist over sampling times and extend over both root systems. The latter relationships were generally weaker, with the two most marked being (i) a tendency in sandy soils for coronal roots at anthesis to have high levels of Rhizoctonia solani, and (ii) for seminal roots at anthesis to have high levels of Heterodera avenae when plants were grown in shallow soils on calcareous rocks, particularly where the farmers applied high levels of superphosphate.
Environmental effects on seed development and hardseededness in Stylosanthes hamata cv. Verano. III. Storage humidity and seed characteristics
Authors: Argel PJ , Humphreys LR
Published: November 2004

Seed pods (upper articulation) from Stylosanthes hamata cv. Verano plants grown at 27,24 and 21�C from flowering onwards were suspended above saturated salt solutions which provided 77, 32, 15 or 6% relative humidity. The seed moisture content which developed after storage in 77 and 32% relative humidity was negatively related, and the degree of hardseededness positively related, to temperature of seed provenance. Seeds formed under high temperature had more lignin (which was concentrated in the counterpalisade cells) and hemicellulose, less cellulose, and shorter palisade cells than seeds formed under cooler temperature. Cutin content was independent of temperature, but the testa of hard seeds exhibited under the scanning electron microscope a more regular, evenly reticulate surface than that of soft seeds. Seed colour changed from dark to light as temperature of seed formation decreased from 27 to 21�C, but hardseededness within each temperature treatment was not consistently associated with seed colour.
The effect of season and nutrition on the resistance of cattle to the tick Boophilus microplus
Authors: Sutherst RW , Kerr JD , Maywald GF , Stegeman DA
Published: November 2004

The host resistance of Bos tauvus (British) and B. indicus x B. tauvus (Zebu x British) steers and heifers to cattle tick (Boophilus microplus) was measured at about monthly intervals for periods of up to 2: years in south-eastern Queensland. The cattle either grazed native pasture, with or without a supplement of lucerne pellets, or were fed entirely on lucerne pellets in yards. Animals grazing native pastures, with poor quality feed in late-autumn and winter, suffered substantial losses of resistance. Up to five times as many ticks survived on them in autumn-winter as in spring-summer, regardless of breed. A less-marked cycle of resistance was observed on all animals fed on lucerne or lucerne supplement, with 2-3 times as many ticks reaching maturity from a constant infestation of larvae in autumn-winter as in spring-summer. Zebu x British steers yielded the same numbers of ticks as heifers in winter but twice as many as heifers in summer. No difference was observed in the yield of ticks from the heifers and steers of British breed at any time. A hypothesis is proposed that the primary cause of the seasonal loss of resistance is the hosts' physiological response to shortening photoperiod. Recovery of resistance is spontaneous once some adaptation to winter conditions has been completed, usually around the time of the winter solstice. Nutritional stress accentuates the loss of resistance and delays its recovery.
Nitrogen loss from protein meals held in terylene bags in the rumen of cattle and the nutritive value of the residues
Authors: Hennessy DW , Lee GJ , Williamson PJ
Published: November 2004

The 'nylon' bag technique was used to measure in the rumen of cattle the loss of nitrogenous compounds ('proteins') from some protein meals available in Australia. There were apparent differences between animals in the proportion of nitrogen (N) remaining from a pelleted meal held in Terylene bags for 15 h in the rumen. When four steers were paired on the basis of minimized standard errors the estimates (� s.e.) of N remaining (46 � 1.1 and 56 � 1.3%) were different (P < 0.05). Pelleting reduced (P < 0.01) the rate of N loss from one of two insoluble N fractions, but had no significant effect on total N loss from a mix of meals. Feeding more protein to steers on a low quality roughage increased their intake of roughage from 14 to 30 g dry matter (kg liveweight)-0 92 day-1 (P < 0.05), and increased the rate of N loss from bags from 2.3 to 4 3 % h-1; this was associated with an increase of rumen ammonia from 5.6 to 140.3 mg N l-1 (P < 0.05). Fish-meal proteins were the most resistant of those tested to fermentative breakdown in the rumen. The estimated proportion of undegraded N (UDN) was 62-81% of total N. The vegetable protein meals were least resistant to losses of N in the rumen (UDN 48-5570 of total N), and the meat meals were the most variable group (UDN 38-61% of total N). Amino acid proportions in the residue of cottonseed meals were relatively unchanged from the original sample, but the remaining N tended to be resistant to an acid pepsin digestion, 46-56% of the residue N being insoluble. A pellet (Agrafpel 79) was compounded from several meals and contained a large fraction of UDN, which had an increased ratio of essential to non-essential amino acids compared with the ratios in the UDN of the separate meals. In addition, the UDN of the pelleted meal was readily digested in acid pepsin. A high proportion of total N as UDN, together with a ready digestion in acid pepsin, are considered important attributes of protein meals for improving the protein nutrition of young cattle.
Canning peach decline in Western Australia. II. Methods of prevention
Authors: Cripps JEL , Doepel RF , McLean GD
Published: November 2004

Previous observations on commercial plantings of the South African canning peach variety Keimoes have linked decline with the entry of a complex of fungi into uncallused pruning wounds and dead crotch bark compressed between scaffold limbs. In field experiments we confirmed that hard winter pruning and narrow crotch limb angles induced crotch wound and pressure cankers. This canker formation and subsequent tree decline was prevented by summer pruning, training trees with wide crotch angles to prevent the formation of compressed dead bark between scaffold limbs, and by the autumn application of an unneutralized spray of copper, zinc and manganese sulfates which inhibit the growth of the fungal invaders. Irrigation and fertilizer treatments had no significant effect on tree health.
Responses of grain sorghum to varying irrigation frequency in the Ord irrigation area. III. Water relations
Authors: Myers RJK , Foale MA , Done AA
Published: November 2004

The water potential (�l), diffusive conductance (gs) and extension rates of leaves were measured throughout the growth of grain sorghum in the dry season at Kimberley Research Station in northwestern Australia. Four cultivars (Quicksilver, Texas 610SR, E57 and 47844) were compared under three furrow irrigation regimens (irrigation every 7-days, 28-days or once-only-at-sowing). Pre-dawn �l, noon �l, noon gs and daily leaf extension rate, between floral initiation and crop physiological maturity, gradually diverged in response to irrigation regimens. There was little difference between cultivars, with pre-dawn �l departing from near zero only after anthesis. Noon �l and gs values fluctuated erratically from day-to-day, perhaps in response to variation in saturation deficit. The effect of irrigation treatment on noon �l, noon gs and leaf extension rate was not obvious until 40-60 days after sowing. Diurnal trends at four stages of growth were measured for the cultivar Texas 610SR which showed partial midday depression of gs, particularly in the drier treatments. Multiple regression analysis of these data showed that variation in �l could largely be explained in terms of radiation, temperature, evapotranspiration (Et) and soil water potential. The best relationship was provided by radiation, temperature and either soil water potential or actual Et (R2 = 0.833). Similarly, much of the variation in g, was related to radiation, temperature, vapour pressure deficit and E,. Multiple regression models, however, failed to describe low midday values of gS observed in water-stressed plants. Although �l, gs and leaf extension responses may be used to compare treatments, none of these measurements could be used as an aid to irrigation scheduling.
Transformations and losses of urea nitrogen after application to flooded rice
Authors: Simpson JR , Freney JR , Wetselaar R , Muirhead WA , Leuning R , Denmead OT
Published: November 2004

Direct measurements of gaseous loss, 15N labelling and intensive sampling of floodwater and soil columns were used to follow the transformations and movement of fertilizer nitrogen (N) applied as urea (80 kg N ha-1) into the floodwater of a young rice crop. During the first 11 days after urea application, about 46% of the applied N was lost from the water-soil-plant system. Only 11% was volatilized as ammonia, despite very high floodwater pH values (up to pH 10) and some strong winds. Gaseous loss as nitrous oxide and leaching of N beyond a soil depth of 100 mm were both negligible. All the evidence indicates that the other 35% of the applied N was lost as dinitrogen produced by denitrification of nitrite and nitrate after nitrification of ammonium near the soil surface. No further losses from the system were detected after the first 11 days. Final recovery of the fertilizer N by the above-ground crop was only 17%. The results show that the several processes which resulted in gaseous loss of N operated concurrently, commencing almost immediately after fertilizer application. The major microbiological transformations appeared to occur near the soil-water interface (c. 0-20 mm depth).
Sulfur nutrition of temperate pasture species. II. A comparison of subterranean clover cultivars, medics and grasses
Authors: Gilbert MA , Robson AD
Published: November 2004

The external and internal requirements for sulfur of five pasture legumes and three grasses of temperate origin were examined in a pot experiment in which plants were grown with seven levels of sulfur supply for 58 days. Nitrogen supply was non-limiting. There was no distinct difference between legumes and grasses in their external requirement for sulfur (i.e. the amount of sulfur required for 90% of maximum yield) or in their sensitivity to sulfur deficiency (i.e. yield at the lowest sulfur supply expressed as a percentage of maximum yield). The requirement for sulfur (mg/pot) fell in the following order: Hunter River lucerne (24) > Jemalong barrel medic (19) > brome grass and Wimmera ryegrass (18) > barley grass (15) > Clare subterranean clover (13) > Trikkala subterranean clover (11) > Seaton Park subterranean clover (10). The high external requirement for sulfur of Hunter River lucerne appears to be due to its poor ability to distribute sulfur from root to shoot and to its high internal requirement for sulfur. However, for Jemalong barrel medic, the high external requirement was solely due to its high internal requirement for sulfur. The higher external requirement for sulfur of the grasses compared with the subterranean clover cultivars appears to be due to the poorer ability of the grasses to obtain sulfur from the soil used in this experiment, rather than to differences in the transfer of sulfur from root to shoot, or in their internal requirement for sulfur.
The productivity of breeding ewes grazing on lucerne or grass and clover pastures on the tablelands of Southern Australia. III. Lamb mortality and weaning percentage
Authors: Donnelly JR
Published: November 2004

Weaning percentage and perinatal mortality of lambs born in late winter or early spring to Merino and Border Leicester x Merino ewes grazing at several stocking rates on lucerne or phalaris-clover pastures were measured over 2 years. Weaning percentages for mature crossbred ewes declined linearly from 136 lambs per 100 ewes joined when stocked at 9 ha-1 to 100 for those at 18 ha-1. For mature Merino ewes, the values were 109 and 70 respectively. Weaning percentages were similar on lucerne and phalaris pastures, although 8% more lambs were born to ewes grazing on phalaris; higher mortality in lambs born as multiples eliminated the difference. Death from exposure during the first 3 days of life was the most important cause of lamb losses. For lambs born as singles to Merino ewes the probability of death from exposure was up to 0.4, and reached 0.6 for lambs born as multiples. For single and multiple lambs born to crossbred ewes equivalent probabilities were 0.25 and 0.4 respectively. These probabilities were reduced if maternal weight was high at lambing, the reduction being of practical significance in very cold weather, particularly if the proportion of multiple births was high. Under mild conditions, where the probability of death from exposure was low, reductions in mortality from high ewe weight at lambing were of little consequence. Long-term weather records kept at the experimental site near Canberra show that a high risk of death in new-born lambs is likely from early June to mid-September. Throughout this period deaths from exposure could be expected to exceed 30% in lambs born as multiples to Merino ewes.
Effect of copper deficiency in wheat on the infection of roots by Gaeumannomyces graminis var. tritici
Authors: Wood MJ , Robson AD
Published: November 2004

Wheat was grown in a soil at five levels of copper (ranging from levels deficient, to those luxurious, for plant growth), in the presence or absence of introduced take-all inoculum (oat kernels colonized by Gaeumannomyces graminis var. tritica). The incidence and severity of take-all were related to the copper supply and hence the copper status of the wheat. Plants grown without applied copper were more severely infected by take-all than were those grown with an adequate or luxurious supply of copper. The number of lesions per gram fresh weight of roots was reduced from 6.5 to 2.4 by increasing the copper supply from that severely deficient, to that adequate for plant growth. In seminal roots, increasing the copper supply from levels severely deficient to those adequate or luxurious for plant growth, decreased the length of proximal lesions (those closest to the seed). By contrast, in nodal roots, a similar increase in copper supply had no effect on the length of proximal lesions, but increased the length of uninfected root between the crown and proximal lesions. In both seminal and nodal roots, copper supply did not affect the intensity of lesions.
Water use efficiency of wheat in a Mediterranean-type environment. II. some limitations to efficiency
Authors: French RJ , Schultz JE
Published: November 2004

Evidence is presented that water use efficiency and yield of wheat are reduced by insufficient leaf area and by inadequate content of nutrients in the top growth. Yields from field trials are compared with the potential yield, and a review is made of the limitations caused by weeds, the incidence of diseases and the harvest index. The data highlight the need for field experiments to define the evaporation and transpiration components of water use in each environment. They also indicate the need for multi-factorial treatments to overcome all yield limitations and thereby attain the potential yield.
An epidemic of cucumber mosaic virus in South Australian lupins
Authors: Alberts E , Hannay J , Randles JW
Published: November 2004

Many Lupinus angustifolius crops in South Australia showed a high incidence of severe stunting and leaf epinasty during 1983. The epidemic was attributed to infection with cucumber mosaic virus. The virus was also recovered from Trifolium subterraneum cv. Geraldton, Medicago polymorpha, Vicia faba, Erodium sp. and Arctotheca calendula growing in or adjacent to lupin crops. The experimental host range of the virus included T. subterraneum cv. Clare, T. repens, Pisurn sativum, Vicia faba and Cicer arietinum. A seed transmission rate of 12-15% was demonstrated in field-infected lupins, and it is concluded that the epidemic probably arose through primary introduction of virus into crops in seed, followed by secondary spread by aphids. The possible role of alternative host species as a reservoir is discussed.
Growth of wheat after damage by, and effects of ethylene dibromide on, a field population of Heterodera avenae
Authors: Stanton JM , Fisher JM
Published: November 2004

Growth of two wheat cultivars (Cook and Egret) after damage by H. avenae, and the effects of EDB on growth and on the nematode were assessed in a field trial. Most early growth variables of both cultivars were delayed by the nematode and EDB largely removed the effects of the nematode. EDB reduced the population of hatched nematodes and delayed hatching of encysted eggs for about 6 weeks, after which hatching resumed. It did not reduce per cent hatch or infectivity. Cook, a later-maturing cultivar than Egret, had more damage on nodal roots when nematode hatching was delayed following treatment with EDB. Both cultivars were equally susceptible to the nematode, but EDB reduced the multiplication of the nematode.
The effect of foliage pathogens on growth of peanuts (Arachis hypogaea L.) in tropical Northern Australia
Authors: Bell M
Published: November 2004

The effect of foliage pathogens on growth and development and final yield of Virginia Bunch peanuts was assessed under tropical wet season conditions in the Ord River Irrigation Area. Applications of the fungicides chlorothalonil and benomyl were used to manipulate onset and severity of disease during the season. Heavy disease pressure in unprotected plots caused severe defoliation and a 30% reduction in commercial yield. This yield reduction, associated with significantly lower pod numbers, was probably due to defoliation causing reduced interception of incident photosynthetically active radiation (PAR) during pod fill and reduced efficiency of conversion of intercepted PAR to reproductive yield. The latter was due to the effect of foliage pathogens on either photosynthetic capacity of remaining leaves, or patterns of assimilate distribution. Data on PAR interception and remaining leaf area alone did not adequately explain the effects of foliage pathogens on crop yield. Canopies with maximum disease control maintained leaf area indices well in excess of that necessary for full interception of incident radiation until maturity. However, commercial yields of pods and kernels from these plots were significantly lower than for those with intermediate foliage protection. This effect was probably due to altered patterns of assimilate distribution between vegetative and reproductive plant parts. The rate of increase in kernel size in fully protected plots was lower than in those with less effective pathogen management, so that a greater proportion of the total pod yield consisted of small, immature pods which were lost during the commercial threshing process.
A comparative analysis of the growth of sweet and forage sorghum crops. I. Dry matter production, phenology and morphology
Authors: Ferraris R , Charles-Edwards DA
Published: November 2004

A sweet sorghum (cv. Wray) and a forage sorghum (cv. Silk) were grown in south-east Queensland without water deficit at two densities in 0.75 m rows on four occasions between late September and mid January. Tiller and branch numbers, and dry matter production, were recorded at appearance of the third leaf ligule, panicle initiation, anthesis, soft-dough stage, maturity and 3 weeks after maturity. Light interception was measured every 2 weeks. The time between all the studied phenological events up to anthesis was shortened with delay in sowing date except for that between appearance of the third ligule and initiation in cv. Silk. The time between anthesis and maturity lengthened with the delay in sowing date of both cultivars. Rate of development was a function of ambient temperature to the third ligule stage and again during maturation. Tiller and branch production were greatest in cv. Silk, decreased with delay in sowing date for both sorghums and was increased by the high density. The estimated assimilate flux required to sustain basal tillers was substantially lower in cv. Silk than in cv. Wray. This flux increased with temperature. In early sown crops, dry matter yields of cv. Wray were greater than those of cv. Silk. Close spacing increased dry matter yields up to anthesis, but by maturity the effect of spacing had been reduced. Cv. Wray produced a larger leaf canopy more rapidly than cv. Silk, although the partitioning of dry matter to leaf tissue only differed between cultivars after canopy closure. The efficiency with which crops used intercepted light energy to produce new above-ground dry matter changed during their ontogeny. It is suggested that early changes in efficiency were a consequence of altered partitioning to roots. The effect of sowing date and spacing on efficiency of light use was slight until the maturation phase, when efficiency decreased with delay in sowing date and at high density. Water use efficiency differed in a similar way to light use efficiency. The relationships found in this study indicate that sorghum growth models need to recognise differences in the morphological development of sorghum types.
Reactions of cyst(e)ine concentration in plasma of Merino sheep from two genetic groups to fasting and ACTH injection
Authors: Williams AJ , Murison RD , Cross CC
Published: November 2004

Two experiments were conducted with two groups of Merino sheep which, as a result of selective breeding, differed in average wool production and average concentration of cyst(e)ine in plasma. In the first experiment, 10 ewes from each flock were fasted for 49 h. Seven blood samples were collected from each ewe and the plasma assayed for total cyst(e)ine (free plus disulfide bound). After an initial decrease in concentration of 2.65 8mol l-1 between 0 and 4 h, the concentration of cyst(e)ine increased linearly throughout the period of fasting (0.22 8mol l-1 h-1). These responses were similar in sheep from the two flocks so that sheep from the high wool producing flock maintained a lower concentration of cyst(e)ine throughout the period of fasting (50.4 v. 60.9 8mol l-1, P < 0.05). In the second experiment, with sheep from the same two genotypes, both cortisol and cyst(e)ine levels in plasma were monitored for 8 h after an injection of synthetic ACTH: 0, 0.2 or 0.4 i.u. kg-I liveweight. Twelve sheep per flock were studied in each of two replicates. Cortisol levels increased following the ACTH injections with the higher dose level giving higher levels of cortisol and more sustained responses for 7 h. The raised cortisol levels were not associated with any changes in the concentration of cyst(e)ine in plasma, and a 17% lower concentration of cyst(e)ine in the sheep of the high producing flock was maintained throughout the experiment. As the raised cortisol levels did not influence the concentrations of cyst(e)ine in plasma of these laboratory sheep, a shed sampling procedure involving venepuncture should be satisfactory for comparisons of the concentration of cyst(e)ine between groups of animals. If the sampling involves extended periods of fasting, some corrections may be necessary to account for the changes in concentration associated with period of fasting.
Digestion of mature pangola grass (Digitaria decumbens) by Bos taurus and Bos indicus cattle
Authors: Hunter RA , Siebert BD
Published: November 2004

The digestion of mature pangola grass (Digitaria decurnbens) by Hereford (Bos taurus) and Brahman (Bos indicus) steers was studied. There was no significant difference between breeds in the digestion of organic matter (OM) and cell wall constituents (CWC). The OM digestibility in the whole tract was 0.59 with 90% of the digestion occurring in the stomachs. There was a significantly (P < 0.05) greater nonammonia nitrogen flow through the abomasum in Herefords (66 g/day) than Brahmans (59 g/day). Likewise the ratio of crude protein digested in the intestines to digestible OM (DCPi:DOMI) was higher (P < 0.05) in Herefords (0.120) than in Brahmans (0.102). In both breeds 66% of the nitrogen associated with the CWC was digested in the whole tract, essentially all digestion occurring in the stomachs. These results for pangola grass, especially the DCPi:DOMI ratios, are compared with the digestion characteristics of other tropical grasses and are discussed in terms of the capacity of tropical grasses to meet the protein requirements of growing cattle.
Quantifying vernalization and temperature promotion effects on time of flowering of three cultivars of Medicago truncatula Gaertn
Authors: Hochman Z
Published: November 2004

The interaction of vernalization and high temperature promotion on the flowering time of three Medicago truncatula cultivars is examined. A previous model describing these processes is modified to account for the hypothesis that temperature promotion of flowering is subsequent to full vernalization. Both models are calibrated to minimize errors in predicting flowering dates from field observations at Condobolin and Tamworth in New South Wales. The calibrated models are then tested on data from other seasons and locations. The implications of the modified model are discussed with regard to an ideotype and to improved efficiency in agronomic evaluation of genetic material.
Response of wheat to single short-term waterlogging during and after stem elongation
Authors: Meyer WS , Barrs HD
Published: November 2004

Transient waterlogging associated with spring irrigations on slowly draining soils causes yield reduction in irrigated wheat. Physiological responses to short-term flooding are not well understood. The aim of this experiment was to monitor above- and below-ground responses of wheat to single waterlogging events during and after stem elongation and to assess the sensitivity of the crop at these growth stages to flooding. Wheat (cv. Bindawarra) was grown in drainage lysimeters of undisturbed cores of Marah clay loam soil. A control treatment (F0) was well-watered throughout the season without surface flooding, while three others were flooded for 96 h at stem elongation (Fl), flag leaf emergence (F2) and anthesis (F3), respectively. Soil water content, soil O2, root length density, leaf and stem growth, apparent photosynthesis (APS), plant nutrient status and grain yield were measured. Soil water content increased and soil O2 levels decreased following flooding; the rate of soil O2 depletion increasing with crop age and root length. Leaf and stem growth and APS increased immediately following flooding, the magnitude of the increases was in the order F1 >F2>F3. A similar order existed in the effect of flooding which decreased the number of roots. Subsequently, leaf and stem growth decreased below that of F0 plants in F1, and briefly in F2. Decreases in APS of treated plants compared to F0 plants appeared to be due to their greater sensitivity to soil water deficit. There was no effect of flooding on grain yield. It is suggested that, while plant sensitivity to flooding decreased with age, flooding at stem elongation had no lasting detrimental effect on yield when post-flood watering was well controlled.
Phosphorus efficiency in pasture species. III. Correlations of dry matter accumulation with phosphorus pool sizes and their net transfer rate
Authors: Chisholm RH , Blair GJ
Published: November 2004

Results of an experiment over five solution P concentrations ( 1 , 2, 4, 8, 16 8M P) and five harvests were used in a response surface approach to determine the size and incorporation rates of major plant P pools in white clover (Trifolium repens cv. Ladino) and stylo (Stylosanthes hamata cv. Verano).At low P stylo had a greater total flux of P from the soluble P (inorganic P, ester P) pool to supply lipid and residue P (RNA, DNA, phosphoprotein) pools.At high P concentrations large soluble P pools in tops were associated with depressed dry weight accumulation in stylo compared to white clover. Possible reasons for this effect of soluble P, as related to photosynthetic rate, are discussed.Since both pool size and incorporation rate affected the efficiency of phosphorus use, the two measures were combined in a model of plant P use to assist in understanding reaction to high or low P. The model demonstrated the importance of maintenance of P supply to structural P pools, particulary phospholipids, at low P levels.Pool size and incorporation rate were combined as a transfer coefficient of P. RGR was best correlated with the transfer coefficients of structural (lipid, residue) pools in the roots rather than the tops. R2 values as high as 0.99 were obtained for relationships between structural P pools and dry weight. Strong correlations were also found when the data of both species were combined, including that the same factors were associated with RGR in different species. Selection for 'P efficiency' based on biochemical parameters is possible, but must take account of roots rather than simpler tops P concentrations.
Responses of pigs fed wheat naturally infected with Fusarium graminearum and containing the mycotoxins 4-deoxynivalenol and zearalenone
Authors: Williams KC , Blaney BJ , Magee MH
Published: November 2004

Wheat naturally infected with Fusariurn graminearurn on a farm in south-eastern Queensland contained mean concentrations of 23 mg 4-deoxynivalenol (DON) kg-1 and 4 mg zearalenone (ZEA) kg-1. No other mycotoxins were detected. The wheat was incorporated into diets containing DON ranging from 0-14 mg kg-1 and corresponding ZEA concentrations. Diets were fed in two experiments to a total of 66 pigs of an improved synthetic breed (half each sex, initial liveweights about 27 kg). The first experiment lasted 14 days and tested short-term responses, while the second was a growth trial lasting up to 14 weeks. Pigs were fasted for 24 h before the diets were first offered. In the first experiment, the pigs ate readily for 10-15 min and thereafter sparingly or not at all for several hours. Vomiting commenced in pigs consuming the most DON after 10-20 min and continued for the next hour. A similiar pattern was seen in the growth trial. In total, vomiting was observed in 13 pigs on the first day of feeding, but not thereafter. Vomiting was accompanied by signs of abdominal distress and teeth grinding. This was followed by marked feed refusal, the extent being related linearly to increasing DON concentrations, so that pigs offered the most DON lost weight during the growth trial. Voluntary feed intake was depressed by about 6% for each 1 mg kg-1 of dietary DON, although some tolerance developed over time. Slight diarrhoea was noted in some pigs, and a few females showed oestrogenic effects due to the ZEA. The feed refusal was well correlated with that obtained by other workers using purified DON. Feed conversion was not adversely affected until DON concentrations exceeded about 8 mg kg-1.
Corrigendum - Effects of soil nitrogen status and rate of inoculation on the establishment of populations of Bradyrhizobium japonicum and on the nodulation of soybeans
Authors: Brockwell J , Gault RR , Morthorpe LJ , Peoples MB , Turner GL , Bergersen FJ
Published: November 2004

Soybeans (Glycine max [L.] Merrill cv. Forrest) were grown under irrigation on a well-structured grey clay soil, previously free of Bradyrhizobium japonicum and containing relatively high levels of mineral N, at Trangie, N.S.W. There were two soil pretreatments, pre-cropped (which had the effect of reducing the level of mineral nitrogen in the soil) and pre-fallowed, and four rates of inoculation (B. japonicum CB 1809 - nil, 0.01 X, 1.OX [=normal] and 100X).Mineral nitrogen (0-10 cm) initially was higher in pre-fallowed soil than in pre-cropped soil (37.6 v. 18.5 mg N per kg). Depletion of mineral nitrogen occurred more rapidly in pre-fallowed treatments, so that, 7 days after harvest, mineral-N in pre-cropped soil was significantly higher than in pre-fallowed soil (14.4 v. 10.6 mg per kg).With high levels of soil mineral nitrogen, colonization of seedling rhizospheres by rhizobia and plant nodulation were diminished. These effects were ameliorated but not eliminated by increased rates of inoculation. The development of the symbiosis was also impeded by lower rates of inoculation (0.01 X, 1.OX).