bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of a preweaning growth restriction on the subsequent growth andmeat quality of yearling steers and heifers
Authors: Hennessy D. W. , Morris S. G.
Published: August 2003

The eating quality of 3 'cuts' of meat was assessed on carcasses of steers (n = 46) and heifers (n = 33) when slaughtered at 17 months of age, following preweaning growth restriction. Growth restriction (for 115 days to weaning) was imposed on half the group ('low'; n = 39 steers and heifers), followed by 2 periods of high-quality nutrition for all animals on (i) pastures (180 days) and (ii) on a grain diet in a feedlot (85 days). Preweaning growth rates (mean and standard error of difference) of steers and heifers on the 'high' treatment (905 v. 838 ± 35.0 g/day) were effectively halved (498 v. 434 ± 35.0 g/day) in the restricted 'low' group. However, no significant compensatory growth occurred when these weight-restricted weaners grazed high-quality pastures, nor during their period in the feedlot. At slaughter, the predicted liveweight of 'high'-growth steers was higher than that of 'low'-growth steers (477 v. 416 ± 11.5 kg) and they had a heavier carcass weight (251 v. 221 ± 7.2 kg). There was no difference between the meat quality (MQ4) scores of meat samples from 'low' or 'high' carcasses in which cuts of blade (2302 'bolar blade', AUS-MEAT 1998) scored higher than rump (2110 'rostbiff', AUS-MEAT 1998) and striploin (2140 striploin, AUS-MEAT 1998) samples. The study has highlighted the persistent effect of undernutrition in early life on final liveweights of Hereford cattle and the consequent reduction in their carcass weight. However, there was no carryover effect of early nutrition on meat quality.
Sequestration of carbon and changes in soil quality under conservation tillage on light-textured soils in Australia: a review
Authors: Chan K. Y. , Heenan D. P. , So H. B.
Published: August 2003

Light-textured soils (<35% clay) make up more than 80%, by area, of cropping soils in Australia. Many have inherent soil physical problems, e.g. hardsetting, sodicity and low organic carbon levels. Maintenance and improvement of soil organic carbon levels are crucial to preserving the soil structure and physical fertility of these soils.A review of field trials on conservation tillage (3–19 years duration) on these soils in southern Australia revealed that significantly higher soil organic carbon levels compared with conventional tillage were found only in the wetter areas (>500 mm) and the differences were restricted to the top 2.5–10.0 cm. The average magnitude of the difference was lower than that reported in the USA. The lack of a positive response to conservation tillage is probably a reflection of a number of factors, namely low crop yield (due to low rainfall), partial removal of stubble by grazing and the high decomposition rate (due to the high temperature). There is evidence suggesting that under continuous cropping in the drier areas, the soil organic carbon level continues to decline, even under conservation tillage.Better soil structure and soil physical properties, namely macro-porosity, aggregate stability and higher infiltration have been reported under conservation tillage when compared with conventional tillage. However, little information on long-term changes of these properties under conservation tillage is available. As many of these soil qualities are associated directly or indirectly with soil organic carbon levels, the lack of significant increase in the latter suggests that many of these improvements may not be sustainable in the longer term, particularly in the drier areas. Continuous monitoring of long-term changes in the soil organic carbon and soil quality under conservation tillage in different agro-ecological zones is needed.
Melilotus albus (Medik.) is productive and regenerates well on saline soils of neutral to alkaline reaction in the high rainfall zone of south-western Victoria
Authors: Evans P. M. , Kearney G. A.
Published: August 2003

Dryland salinity is a serious problem in Australia. While some introduced perennial grasses such as tall wheat grass (TWG) Thinopyrum ponticum (Podp. Z.W. Liu & R.R.C. Wang) are adapted to saline soils, there are few pasture legumes that are productive and persistent under saline conditions. Melilotus albus (Medik.) has the potential to be 1 such legume in southern Australia. To test the potential of this species, we conducted 2 experiments over a 3-year period on saline soils at Woorndoo and Glenthompson in south-western Victoria. The soil electrical conductivities (1 : 5 water) of the sites, in autumn before sowing, were 1–3 dS/m at Woorndoo and 3–5 dS/m at Glenthompson (0–10 cm depth).At both sites the herbage yields of 2 Melilotus lines were greater than 10 t/ha of dry matter for the whole season between autumn and late summer. The best commercial control species at Woorndoo, white clover cv. Haifa, produced less than 1/6 of the yield of the best Melilotus line during the summer months. At Glenthompson, during the whole second season the herbage yield of the best Melilotus was 40% greater than that of the best commercial control, Persian clover cv. Nitro plus. In the second season, regeneration of Melilotus at both sites was excellent, averaging 3500 seedlings/m2 at Woorndoo, and 1100 and 3400 seedlings/m2 in mixtures with TWG and in monoculture, respectively at Glenthompson. In the third season, however, regeneration averaged only 400 plants/m2 at Woorndoo and 640 plants/m2 at Glenthompson, both with and without grass. It appears that, when there is limited competition, Melilotus albus dominates in the first 2 years. However, as fertility and water use increase, other pasture species, which initially have a low rate of survival and are unproductive, begin to increase their presence in the sward at the expense of M. albus. These annual species germinate after the autumn rains dilute the salt on the surface of the soil and senesce in early summer as soil water deficits and/or evaporation increase the electrical conductivity again. We suggest that Melilotus albus is an excellent pasture legume to revegetate saline soils in southern Australia and represents an opportunity to obtain high levels of out-of-season pasture production from areas that are currently unproductive.
Performance of some perennial grasses on severely salinised sites on the inland slopes of New South Wales
Authors: Semple W. S. , Cole I. A. , Koen T. B.
Published: August 2003

Thirty perennial grass accessions were evaluated for emergence, growth and persistence at 6 severely salinised seepage scalds on the western slopes of New South Wales. Warm-season accessions were sown or planted in spring 1996 and 1997, and cool-season types in autumn 1996 and 1997. Control species, tall wheat grass (Thinopyrum ponticum) and puccinellia (Puccinellia ciliata) were sown in spring and autumn. Plants were monitored over 2 growing seasons. None of the accessions, including the controls, performed well at all sites. Of the accessions established from seed, tall wheat grass was the most reliable in terms of the number of successful establishments but its growth potential was only achieved at a few sites. Some warm-season species (Panicum coloratum, Chloris gayana and Cynodon dactylon) approached their growth potential at some sites but overall rates of establishment were very low. The performance of puccinellia appeared to be adversely affected by low pH. It was concluded that on severely scalded sites, vegetative propagation of stoloniferous–rhizomatous plants, e.g. Pennisetum clandestinum, Paspalum vaginatum and C. gayana, may be the best option.
Effect of grain and straw supplementation on marginal milk-production responses and rumen fermentation of cows grazing highly digestible subterranean clover pasture
Authors: Wales W. J. , Doyle P. T.
Published: August 2003

The marginal milk-production response to cereal grain supplementation of dairy cows grazing irrigated subterranean clover (Trifolium subterraneum L.) pasture in spring was investigated. We also determined whether the addition of a perennial ryegrass (Lolium perenne L.) straw supplement would improve that response. There were 8�replicated treatments in a factorial design with 2 amounts of cereal grain pellet [0 and 5.0 kg dry matter (DM)/cow.day] and 4 amounts of straw (0, 0.5, 1.0 and 2.0 kg DM/cow.day), 48 cows in total. Cows in all treatments grazed subterranean clover at an allowance (measured to ground level) of 19 kg DM/day. The barley and wheat pellet and straw had a neutral detergent fibre (NDF) concentration of 164 g/kg DM and 704 g/kg DM, respectively. Cows from all treatments consumed pasture with an in vitro DM digestibility of 743�g/kg DM and NDF concentration of 313 g/kg DM, compared with the pregrazed pasture on offer of 707 and 360, respectively. Pasture DM intake was not affected (P>0.05) by supplementation with either grain or straw, and averaged 12.7�kg�DM/cow.day. Cows supplemented with grain achieved a marginal milk-production response of 1.0�kg�fat-corrected milk (FCM)/kg DM grain. However, with increasing amounts of straw, responses of 0.0, 0.9 and 0.5 kg FCM/kg DM grain were observed. Fat-corrected milk yields were not different (P>0.05) between straw treatments and averaged 25.8 kg FCM/cow.day. Grain feeding significantly (P<0.05) reduced milk fat concentration and increased (P<0.05) milk protein concentration, although offering increasing amounts of straw had no significant (P>0.05) effect on either milk fat or milk protein concentration. Average ruminal fluid pH was significantly (P<0.05) lower when cows consumed cereal grain pellets than with those treatments without cereal grain (5.82 v. 6.09). There were no differences (P>0.05) in ruminal fluid pH among cows that consumed different amounts of straw. When cows were managed to limit intake of subterranean clover by restricting pasture allowance, supplementation with cereal grain resulted in acceptable marginal milk-production responses of 1.0 kg FCM/kg DM cereal grain. Under these circumstances, providing additional NDF as straw did not improve the milk-production response to cereal grain, with NDF ranging from 290 to 337 g/kg DM when 0–1.7 kg DM straw was consumed.
Secretion of milk and milk components in sheep
Authors: Bencini R. , Knight T. W. , Hartmann P. E.
Published: August 2003

The effect of milking intervals of 4–20 h and of milking frequencies of 1–6 times a day on the rate of secretion of milk and milk components was determined in 2 breeds of sheep unselected for dairy production, the Australian Merino and the New Zealand Poll Dorset. The rate of milk secretion was greater after short intervals and after increased milking frequencies, indicating that in sheep the rate of milk secretion in the short term is regulated by a local feedback mechanism. After short intervals between milkings, the fat concentration in the milk was higher (99.5 ± 6.21 g/kg) and the protein concentration was lower (about 65 ± 2.89 g/kg) than after long intervals between milkings. This was not due to the presence of residual milk left in the mammary glands as subsequent experiments gave similar results when the residual milk was removed with the aid of oxytocin. We obtained similar responses if ewes were exposed to a series of 4 consecutive milkings to remove possible carry-over effects of the previous interval and achieve a constant volume of residual milk. We concluded that in sheep the rate of secretion of fat decreases while that of protein increases with time after milking and that the synthesis of fat and protein are controlled by at least 2 different mechanisms. This might be due to the fact that, unlike dairy cows and goats, sheep have not been subjected to selective pressure for dairy production.
Effects of nitrogen fertiliser on potato (Solanum tuberosum L., cv. Russet Burbank) in Tasmania. 1. Yield and quality
Authors: Sparrow L. A. , Chapman K. S. R.
Published: August 2003

Thirteen field trials were conducted on ferrosols and tenosols in Tasmania to assess the response of potatoes (Solanum tuberosum L., cv. Russet Burbank) to basal (up to 250 kg/ha) and topdressed (up to 100 kg/ha) nitrogen fertiliser. Economic yield responses to basal nitrogen were obtained at 9 sites. Topdressing did not increase yield compared with equivalent rates of basal nitrogen, and often failed to compensate for a lack of nitrogen applied at planting. This lack of response may reflect the inability of the potato crop to make use of nitrogen applied during tuber bulking. Nitrogen fertiliser decreased tuber specific gravity at several sites. The effects of nitrogen on misshapen tubers, bruising susceptibility, crisp colour and hollow heart were inconsistent and often of no practical importance. However, at 2 sites, nitrogen fertiliser increased yields of misshapen tubers at the expense of processing tuber yields. At 1 of these sites, nitrogen topdressing decreased the yield of misshapen tubers. Otherwise, topdressing had similar effects on tuber quality to those of basal nitrogen. Growers should fertilise with nitrogen to optimise their yields. Optimum rates were greater in paddocks that had been continuously cropped for more than 10 years (average rate 193 kg/ha), than in those that had been in pasture (average rate 48 kg/ha).
Effects of nitrogen fertiliser on potato (Solanum tuberosum L., cv. Russet Burbank) in Tasmania. 2. Petiole and soil analysis
Authors: Sparrow L. A. , Chapman K. S. R.
Published: August 2003

Thirteen field trials were conducted on ferrosols and tenosols in Tasmania to assess the response of potatoes (Solanum tuberosum L., cv. Russet Burbank) to basal and topdressed nitrogen fertiliser. The objectives of this study were to assess whether petiole nitrate concentrations could be used to indicate potato nitrogen status and crop response to nitrogen topdressing, and whether various soil nitrogen measures could be used to determine the responsiveness of potatoes to nitrogen fertilisation. Petiole nitrate-nitrogen concentrations in the youngest fully expanded leaves were found to be an indicator of nitrogen status. Critical nitrate concentrations varied in a linear fashion from about 25 000 mg/kg at tuber initiation to less than 5000 mg/kg when tubers were 100 mm long (about 100 days after planting). These concentrations are consistent with those determined for Russet Burbank in other studies. In contrast to petiole measures, various pre-plant and early season soil nitrogen measures (mineral, mineralisable and total nitrogen) did not adequately (adjusted R2<0.25) explain variation in crop nitrogen responsiveness and could not be recommended as diagnostic or predictive tests. Soil nitrogen mineralisation rates in spring varied from 0.4 to 5 kg N/ha.day and were higher at sites previously in pasture than at continuously cropped sites. Although petiole nitrate concentrations responded to nitrogen topdressing, most nitrogen-deficient crops in this study did not show yield responses to topdressed nitrogen. This limited the usefulness of petiole nitrate-nitrogen tests.
Foam stability and buffering capacity in cultivars of lucerne (alfalfa)
Authors: Gregory N. G. , Auricht G. C.
Published: August 2003

When lucerne is used for making silage it is prone to developing inferior quality because of a high pH. When lucerne is directly grazed by livestock it is prone to causing bloat, which can be lethal for individual animals. This project examined whether there are cultivar differences in buffering capacity and hence silage-making quality, and in foam stability in leaf extracts and hence the likely persistence of foam in the digesta of the animal. If differences exist, it should be possible either to choose cultivars that are less prone to these problems or to genetically select for superior silage-making and low bloat potential properties using the superior cultivars. Leaf extracts from 12 lucerne cultivars were screened for foam stability, and 32 cultivars were screened for buffering capacity. There were significant differences between 3 cultivars (Sceptre, Aurora and Cimarron) for foam stability, and between 4 cultivars (PL 55, SARDI 66, Trifecta and Oro) for buffering capacity. There was sufficient variation in both characteristics to warrant testing the inclusion of these traits in a lucerne breeding program. All the cultivars tested for silage pH had an unacceptably high pH, even those with lower buffering capacities. This indicated that it would be inappropriate to promote the existing low buffering capacity cultivars as suitable for silage, and that further selection for lower buffering capacity is needed.
Distribution and density of the root system of macadamia on krasnozem soil and some effects of legume groundcovers on fibrous root density
Authors: Firth D. J. , Whalley R. D. B. , Johns G. G.
Published: August 2003

Whole-tree excavations, root-core and minirhizotron studies indicate that the grafted macadamia tree root system is relatively shallow and spreading, with a short taproot and most of the fibrous root system near the soil surface, while ungrafted trees have a longer taproot. The length of fibrous roots diminished with depth and distance from the trunk. This pattern is consistent with other fruit trees, in that the highest density is generally within 1 m of the trunk. Values obtained in core samples in this study were 4.97 (± 0.43) cm/cm3 and 1.67 (± 0.45) cm/cm3 for 0–10 cm and 10–20 cm at 0.5 m from the trunk, and 2.34 and 1.08 cm/cm3, respectively, at 1 m from the trunk at Clunes. These values were similar to those obtained in separate studies in 1991–93, involving assessments at 5�cm depth increments down to 15 cm, where mean root length densities were 2.0–3.5 cm/cm3 and 1.3–1.9 cm/cm3 at 0–5 cm and 5–15 cm depth, respectively, 1.4 m from the trunk. Root length under old trees in bare soil at Dorroughby and Clunes, using minirhizotrons (0.25–0.40 cm/cm2) and soil cores (1.14 and 3.50 cm/cm3, respectively), was similar to that found at other sites in the study area (minirhizotrons 0.28–0.33 cm/cm2; soil cores 1.25–2.80 cm/cm3). There is an apparent lower rate of decrease in root length density with increasing distance from the trunk at 10–20 cm compared with 0–10 cm. New root growth occurred predominantly in autumn, but some new fibrous roots were produced in early winter and spring. Proteoid roots were found in abundance in soil cores and adjacent to minirhizotron tubes and there were more of them in the root systems of younger trees at Clunes than with older trees at Dorroughby. Proteoid roots were found at a greater depth than previously recorded for other Proteaceae species, and appeared to retain their function in relatively dry conditions for more than a year. Non-proteoid fibrous roots at the minirhizotron surface appeared to be functional for about 1.5 years in relatively dry conditions, before decay after the onset of wet soil conditions.The effects of 2 newly established perennial legume groundcovers on the root systems of younger and older macadamia trees were studied over 2.5 years. In general, the presence of groundcover either had no effect on the growth of the macadamia roots or increased the root length density at some sampling dates and some depths. At Clunes, where the proteoid root length density was higher than at Dorroughby, the presence of groundcover was associated with higher proteoid root length density than that with bare ground. Arachis pintoi cv. Amarillo generally had a lower root length density than Lotus pedunculatus.
Calcium treatment of harvested Geraldton waxflower does not enhance postharvest quality
Authors: Taylor M. N. , Joyce D. C. , Wearing A. H. , Simons D. H.
Published: August 2003

Postharvest flower abscission from cut Geraldton waxflower (Chamelaucium uncinatum) is mostly caused by fungal invasion. Elevated plant tissue calcium concentrations through postharvest application reduces fungal disease severity in various crops. Such results may be explained by strengthening of plant cell walls by calcium. Strengthening provides a structural barrier to fungal hyphae, thereby restricting invasion of plant cells. Postharvest pulsing with calcium solution substantially increased calcium concentrations in waxflower tissues. 45Ca�tracer revealed calcium distribution throughout flowering sprigs, including infection sites such as stylar tissue. However, pulsing waxflower sprigs with calcium did not suppress either disease or flower abscission, nor did it enhance vase life.
Effects of continuous and seasonal grazing strategies on the herbage mass, persistence, animal productivity and soil water content of a Sirosa phalaris - subterranean clover pasture, North-West Slopes, New South Wales
Authors: Lodge G. M. , Murphy S. R. , Harden S.
Published: August 2003

An experimental site was established in 1997 on the North-West Slopes of New South Wales to further investigate the use of strategic grazing management to improve the persistence of phalaris (Phalaris aquatica cv.�Sirosa) and subsequent effects on animal production and soil water content. The pasture was sown in 1992 to Sirosa phalaris, subterranean clover (Trifolium subterraneum var. subterraneum cv. Seaton Park) and lucerne (Medicago sativa cv. Aurora). Four grazing treatments were applied in a randomised 3-replicate design. Treatments consisted of continuous grazing at 12.3 sheep/ha (C12 or control); continuous grazing at 6 sheep/ha (C6), and 2� spring and autumn strategies of either resting from grazing for 6 weeks in each season (SAR0), or reducing stocking rate from 12.3 to 4.0 sheep/ha (SAR4). Despite annual applications of fertiliser and high clover content, Sirosa phalaris herbage mass in plots continuously grazed at 12.3 sheep/ha declined from a mean of 3300 kg DM/ha in spring 1997 to < 700 kg DM/ha by May 1998. At the end of the study (February 2001), Sirosa mean herbage mass in these plots was 670 kg DM/ha and lower (P < 0.05) than for the other treatments (mean value 5400 kg DM/ha). These marked changes in herbage mass, and the degradation of the Sirosa-based pasture to an annual pasture by continuous grazing at 12.3 sheep/ha, were not generally reflected in either short-term animal production or substantial differences in soil water content. Wool production (kg/head) was not significantly different among treatments each year. Compared with continuous grazing at 12.3 sheep/ha, sheep liveweights were higher (P < 0.05) in plots continuously grazed at 6.1 sheep/ha from November 1997 to February 1999. However, from February 1999 to 2001, sheep liveweights in the 2 treatments with the highest Sirosa phalaris content were lower (P < 0.05) than those continuously grazed at 12.3 sheep/ha. Only the soil water content for the C6 and SAR4 treatments at 0–30�cm was significantly different to the control treatment, but the differences were predicted to be < 2.5 mm/year. In the root zone (0–90 cm), mean soil water content ranged from 159 to 309 mm (mean 220 mm), while plant available water (soil water content – soil water content at –1500 kPa) was a mean of 79 mm, ranging from 11 to 168 mm.
The effect of ReTain plant growth regulator [aminoethoxyvinylglycine (AVG)] on the postharvest storage life of 'Tegan Blue' plums
Authors: Jobling J. , Pradhan R. , Morris S. C. , Mitchell L. , Rath A. C.
Published: August 2003

ReTain plant growth regulator is a commercial formulation of aminoethoxyvinylglycine (AVG). This compound is known to competitively inhibit the activity of the enzyme ACC (1-aminocyclopropanecarboxylate) synthase which is the rate limiting enzyme in the ethylene biosynthesis pathway. By inhibiting the activity of ACC synthase, ethylene-mediated ripening processes can be delayed.'Tegan Blue' plums have low ethylene production, which indicates that it is a suppressed climacteric variety. There was a significant difference between the ReTain treated and untreated fruit for the second harvest, this difference was greater later in storage than early in storage. The results indicate that there is a postharvest benefit achieved after applying AVG to 'Tegan Blue' plums. The main advantage is in the maintenance of firmness for late-harvested fruit. Other benefits are the suppression of ethylene production and the development of a more intense colour.
Relating cultivar Pachymetra root rot resistance to sugarcane yield using breeding selection trial analyses
Authors: Magarey R. C. , Bull J. I.
Published: August 2003

Plant breeders conduct a range of yield trials each year to estimate the yielding potential of sugarcane clones progressing through the breeding program. Only the highest-yielding clones are selected for further testing with very small numbers being released as commercial cultivars. Disease susceptibility varies greatly amongst the tested clones and a number of diseases influence the yield of clones in various stages of the selection process. Disease resistance testing is an important routine aspect of the breeding program. All clones for northern Queensland are screened for disease resistance, while selected clones from other areas are tested for resistance to Pachymetra root rot. Two new terms are introduced: resistance index (RI) and the yield loss resistance index (YLRI). Analyses were conducted relating yielding ability of clones in stage 3 trials to Pachymetra resistance. Pachymetra root rot on average reduced tonnes cane per hectare by 15.8% and tonnes sugar per hectare by 10.2%. There was a slight positive effect on commercial cane sugar. YLRI5 for tonnes cane was 3.5 and for tonnes sugar 5.7. With a RI of 3.7, the current breeding strategy for northern Queensland appears appropriate. The data reported here will be valuable for refining selection strategies to improve breeding efficiencies. These analyses could be undertaken each year using data from all breeding trials throughout Queensland, not only with Pachymetra root rot, but also with other diseases normally endemic in cane fields. The advantage of this technique is that with a minimum of further expenditure, ongoing estimates of disease-induced yield losses can be obtained with the information guiding the selection program.
Total and phytate-phosphorus contents and phytase activity ofAustralian-sourced feed ingredients for pigs and poultry
Authors: Selle P. H. , Walker A. R. , Bryden W. L.
Published: August 2003

A total of 160 samples of 20 Australian-sourced feed ingredients of plant origin for pigs and poultry was analysed for total phosphorus and phytate-phosphorus contents and endogenous phytase activity. The majority of total P was present as phytate-phosphorus, and these concentrations were significantly correlated in 9 feed ingredients. The endogenous phytase activity in tested feed ingredients was negligible other than for wheat, its by-products and barley. Phytate-phosphorus was determined by a standard 'ferric chloride precipitation' method, which was satisfactory for individual feed ingredients, with the exception of lupins and faba beans. It appears that phytate is more difficult to extract from these two feedstuffs, possibly because of the affinity of phytate for protein. Ferric chloride precipitation methods are not suitable for phytate-phosphorus determinations of complete feed samples containing other sources of phosphorus, which is a distinct limitation. A lesser limitation is that these methods cannot distinguish between the various esters of myo-inositol phosphate present. Given the variation of phytate contents within ingredients, particularly wheat, the desirability of determining dietary substrate levels is emphasised to take full advantage of including exogenous phytases in pig and poultry diets to reduce phosphorus excretion and abate phosphorus pollution.
The potential of Brassica green manure crops for controlling root-knot nematode (Meloidogyne javanica) on horticultural crops in a subtropical environment
Authors: Stirling G. R. , Stirling A. M.
Published: August 2003

In glasshouse experiments, Meloidogyne javanica reproduced on Brassica juncea, B. napus and BQMulch, a commercial biofumigant crop consisting of both B. napus and B. campestris. Although nematode multiplication rates were only 3–23% of the rate on a highly susceptible crop (tomato), they were high enough to suggest that Brassica rotation crops will increase root-knot nematode populations to potentially damaging levels in situations where temperatures do not limit nematode reproduction. A field study showed that this problem could be prevented in subtropical climates by restricting the growth of Brassica crops to June, July and August, when low temperatures limit nematode development and eggs are not produced until about 10 weeks after planting. Field and pot experiments in which M. javanica was introduced into soil following incorporation of Brassica residues failed to demonstrate a 'biofumigation' effect, possibly because the soil was too dry or the degree of tissue disruption was insufficient to maximise isothiocyanate release. Numbers of root-knot nematodes were reduced when Brassica roots, leaves and stems were incorporated into soil at 17 t DM/ha, but it is unlikely that this was due to the production of nematoxic chemicals, as large numbers of free-living nematodes multiplied during the decomposition process. From a practical perspective, these results suggest that green-manured Brassica rotation crops are unlikely to be useful for controlling root-knot nematodes on some subtropical horticultural crops that are currently fumigated for nematode control. The susceptibility of brassicas to M. javanica and the need to grow them during winter limits their potential in the vegetable industry, while difficulties in obtaining a biofumigation effect in dry soil will reduce effectiveness in non-irrigated pineapple soils. Brassicas are likely to be most useful in the ginger industry, as they can be grown during the winter break between ginger crops and fields can be irrigated before the Brassica crop is incorporated into soil.
A simple method to improve field-level rice identification: toward operational monitoring with satellite remote sensing
Authors: Niel T. G. Van , McVicar T. R.
Published: August 2003

Discriminating crops by remote sensing remains reasonably complex and expensive for many agricultural land managers. The current study was conducted to facilitate the operational use of remote sensing for field-level rice monitoring in Australia by determining (i) whether existing methods relating to simple moisture-based rice classification could be further simplified, and (ii) whether the high accuracies resulting from that moisture-based methodology could be further increased. First, the impact of removing the most complicated processing step, atmospheric correction, on rice classification accuracies was assessed for the 2000–01 summer growing season at the Coleambally Irrigation Area, New South Wales. The primary error sources of rice classification were then identified and simple rules developed in an attempt to reduce errors associated with confusion between unharvested winter cereals and flooded rice paddies early in the summer growing season. These newly defined rules were then used on imagery acquired in the subsequent summer growing season (2001–02) in order to assess their repeatability. The assessment of atmospheric correction showed that during the critical time frame associated with high rice identification (October–November), using non-atmospherically corrected data increased overall accuracy, although the improvement was small (about 1%). Overall accuracy also increased for every case tested for both growing seasons as a result of the rule-based classification (ranging from about 1 to 14%), revealing that the methods were sufficiently repeatable. This study moves per-field rice monitoring at the Coleambally Irrigation Area closer to an operational application and shows that simple rule-based remote sensing classifications can be very effective when site practices are known.
Understanding plant responses to drought — from genes to the whole plant
Authors: Chaves Manuela M. , Maroco João P. , Pereira João S.
Published: August 2003

In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought — such as phenology, root size and depth, hydraulic conductivity and the storage of reserves — are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype–phenotype gap to be bridged, which is essential for faster progress in stress biology research.
Peroxidase: a multifunctional enzyme in grapevines
Authors: Barceló Alfonso Ros , Pomar Federico , López-Serrano Matías , Pedreño Maria Angeles
Published: August 2003

Peroxidases are heme-containing enzymes that catalyse the one-electron oxidation of several substrates at the expense of H2O2. They are probably encoded by a large multigene family in grapevines, and therefore show a high degree of polymorphism. Grapevine peroxidases are glycoproteins of high thermal stability, whose molecular weight usually ranges from 35 to 45 kDa. Their visible spectrum shows absorption bands characteristic of high-spin class III peroxidases. Grapevine peroxidases are capable of accepting a wide range of natural compounds as substrates, such as the cell wall protein extensin, plant growth regulators such as IAA, and phenolics such as benzoic acids, stilbenes, flavonols, cinnamyl alcohols and anthocyanins. They are located in cell walls and vacuoles. These locations are in accordance with their key role in determining the final cell wall architecture, especially regarding lignin deposition and extensin insolubilization, and the turnover of vacuolar phenolic metabolites, a task that also forms part of the molecular program of disease resistance. Although peroxidase is a constitutive enzyme in grapevines, its levels are strongly modulated during plant cell development and in response to both biotic and abiotic environmental factors. To gain an insight into the metabolic regulation of peroxidase, several authors have studied how grapevine peroxidase and H2O2 levels change in response to a changing environment. Nevertheless, the results obtained are not always easy to interpret. Despite such difficulties, the response of the peroxidase–H2O2 system to both UV-C radiation and Trichoderma viride elicitors is worthy of study. Both UV-C and T. viride elicitors induce specific changes in peroxidase isoenzyme / H2O2 levels, which result in specific changes in grapevine physiology and metabolism. In the case of T. viride-elicited grapevine cells, they show a particular mechanism for H2O2 production, in which NADPH oxidase-like activities are apparently not involved. However, they offer a unique system whereby the metabolic regulation of peroxidase by H2O2, with all its cross-talks and downstream signals, may be elegantly dissected.
Cytokinin metabolism in Narcissus bulbs: chilling promotes acetylation of zeatin riboside
Authors: Letham David S. , Smith Noel G. , Willcocks David A.
Published: August 2003

The levels of the cytokinins zeatin, dihydrozeatin and N6-(isopent-2-enyl)adenine and the corresponding 9-ribosides were determined in whole Narcissus pseudonarcissus L. bulbs after onset of summer dormancy, and after storage of the dormant bulbs at 4 or 15°C under moist conditions. The cytokinin level was increased at both temperatures; the dominant cytokinin at 15°C was zeatin riboside but at 4°C the free base, zeatin, was the principal cytokinin. The metabolism of 3H-labelled zeatin, zeatin riboside and 6-benzylaminopurine was studied in scales and base plates excised from bulbs previously held at 4 or 15°C. The chilling treatment promoted conversion of [3H]zeatin riboside to O-acetylzeatin riboside (an unusual cytokinin metabolite) in the excised base plate and inhibited 9-riboside formation from 6-benzylaminopurine. Chilling also promoted formation of O-acetylzeatin riboside from [3H]zeatin in excised scale tissue. Endogenous O-acetylzeatin and O-acetylzeatin riboside were concentrated in the base plate. Relative to zeatin riboside, O-acetylzeatin riboside was degraded to adenosine and related compounds less rapidly in the leaf cluster. Since acetylation of the zeatin side chain enhances activity in cytokinin bioassays, O-acetylzeatin riboside may play a role in leaf development following chilling of Narcissus bulbs.
A ten-year study on the physiology of two Spanish grapevine cultivars under field conditions: effects of water availability from leaf photosynthesis to grape yield and quality
Authors: Medrano Hipólito , Escalona José M. , Cifre Josep , Bota Josefina , Flexas Jaume
Published: August 2003

The effects of moderate irrigation, compared with non-irrigation, on leaf photosynthesis and transpiration, grape yield, and quality parameters, were studied over ten years in two Spanish cultivars (Tempranillo and Manto Negro) of field-grown grapevines (Vitis vinifera L.). The aim was to increase our knowledge of the relationships between water availability, canopy water losses, photosynthesis, and fruit yield and quality. A second aim was to analyse some of the mechanisms of photosynthetic down-regulation under drought, such as the capacity for RuBP regeneration and Rubisco activity.Moderate irrigation improved plant water status, leaf photosynthesis and transpiration. Considering the results over ten years, soil water availability (estimated as pre-dawn leaf water potential, ΨPD) largely determined leaf photosynthesis and leaf transpiration. Decreased photosynthesis was due to both stomatal and non-stomatal factors. The latter were related to decayed electron transport rate and reduced RuBP regeneration capacity, but not to decreased Rubisco activity.Moderate irrigation also improved grape yield, although this effect was much larger in Tempranillo than in Manto Negro. Moreover, the correlation between photosynthesis and grape yield was significant in Tempranillo, but not in Manto Negro. In contrast, the correlation between ΨPD and several parameters reflecting fruit quality (such as soluble solids and total polyphenol content) was significant only in Manto Negro. These results suggest that there is a close link between water availability and grape yield, mostly through water stress effects on photosynthesis. Drought effects on grape quality are linked to water availability but not to photosynthesis or yield.
Describing and modelling ozone-dependent variation in flavonoid content of bean (Phaseolus vulgaris cv. Bergamo) leaves: a particular dose - response relationship analysis
Authors: Kanoun Myriam , Goulas Philippe , Biolley Jean-Philippe
Published: August 2003

We investigated the ozone-dependent variation in the amount of a flavonoid accumulated by bean leaves (Phaseolus vulgaris L. cv. Bergamo). The phenolic response was modelled with special regard to different ozone exposure indexes. Using open-top chamber technology, six atmospheres of increasing ozone concentration were tested. Four successive harvests were carried out during a 33-d experiment. Primary and first trifoliate leaves were collected. Visible foliar injuries were recorded and the quantification of an ozone-responsive flavonoid was achieved by HPLC. Ozone significantly increased the amount of kaempferol glucuronide, which normally decreased with leaf ageing. Depending on the leaf type, this increase occurred either before or after the appearance of visible foliar damage. A linear regression could account for the ozone dose–phenolic response relationship. However, with respect to leaf type, the agreement between the model and observed values was influenced by the way in which ozone dose was calculated. Among the ozone exposure indexes tested, only the index with the highest threshold (AOT60) was appropriate to make the phenolic response linear in the case of primary leaves while in the case of first trifoliate leaves, this index always displayed the poorest adjustment compared with SUM00, SUM60, and AOT40 indexes. The study of the relationship suggests that sensitivity to ozone could be dependent on leaf type.
New insights into grapevine flowering
Authors: Boss Paul K. , Buckeridge Elise J. , Poole Andrew , Thomas Mark R.
Published: August 2003

The study of grapevine (Vitis spp.) flowering has unique challenges owing to the unique shoot architecture of the plant and the arrest of the flowering process during winter. The grapevine flowering process: inflorescence number per vine, flower number per inflorescence, fruit set and growth has a major impact on fruitfulness (berries per hectare) and hence yield. This review brings together past research into the biology and physiology of grapevine flowering with recent investigations of genes involved in flowering. Genes involved in floral induction and inhibition by gibberellins (GA insensitive), meristem identity (LEAFY, TERMINAL FLOWER1) and organ identity (MADS-box genes) are discussed. An understanding of the function of key genes controlling the development of uncommitted primordia, floral induction and development, and fruit set in grapevine will provide new opportunities for improving vineyard fruitfulness. Understanding the grapevine floral genetic network will also offer insight into the different evolutionary strategies employed by plants to ensure reproduction.
Assessment of photoprotection mechanisms of grapevines at low temperature
Authors: Hendrickson Luke , Ball Marilyn C. , Osmond C. Barry , Furbank Robert T. , Chow Wah Soon
Published: August 2003

The photosynthetic response of grapevine leaves (Vitis vinifera L. cv. Riesling) to low temperature was studied in the field and laboratory. Light-saturated rates of photosynthetic electron transport were lower and non-photochemical energy dissipation was higher when leaves were subject to low morning temperatures than to high afternoon temperatures under field conditions. These responses to low temperatures occurred without sustained reduction of quantum efficiency of PSII as measured by the variable to maximum chlorophyll fluorescence yield ratio, Fv/Fm, after dark adaptation. The temperature dependence of light-saturated apparent electron transport rate, gas exchange and non-photochemical quenching (NPQ) was also examined in laboratory experiments with glasshouse-grown material. NPQ reached saturation at lower light intensity with decreasing temperature. The relationship between the quantum efficiency of PSII and CO2 fixation at 25°C (2–21% O2) and 10°C (2–21% O2) indicated a decreased dependence of electron transport on both photorespiration and the Mehler reaction at the lower temperature. The calculated percentage of electron flow to the Mehler reaction declined faster than photorespiration at low temperature. Warm- and cold-treated leaf discs under saturating light showed very little photoinhibition as measured by sustained reduction in Fv/Fm, which was linearly related to the percentage of functional PSII reaction centres. However, the addition of dithiothreitol greatly enhanced the rate of photoinhibition, indicating a potentially strong dependence on xanthophyll de-epoxidation for photoprotection at low temperature.
Partial rootzone drying: regulation of stomatal aperture and carbon assimilation in field-grown grapevines (Vitis vinifera cv. Moscatel)
Authors: Souza Claudia R. de , Maroco João P. , Santos Tiago P. dos , Rodrigues M. Lucília , Lopes Carlos M. , Pereira João S. , Chaves M. Manuela
Published: August 2003

The effects of 'partial rootzone drying' (PRD) irrigation compared with other irrigation systems, namely non-irrigated (NI), full irrigation (FI) and deficit irrigation (DI), on stomatal conductance and carbon assimilation were evaluated in field-grown grapevines (Vitis vinifera L. cv. Moscatel). At the end of the growing season, pre-dawn leaf water potential was highest in FI (–0.18 ± 0.01 MPa; mean ± s.e.), intermediate in PRD (–0.30�± 0.01 MPa) and DI (–0.36 ± 0.02 MPa), and lowest in NI vines (–0.64 ± 0.03 MPa). Stomatal conductance measured under controlled conditions of light and temperature was reduced in NI (ca 60%) and PRD (ca 30%) vines compared with DI and FI vines. Under ambient conditions, NI vines had lower rates of stomatal conductance (ca��26%), net CO2 assimilation (ca 28%) and light-adapted PSII quantum yields (ca 47%) than PRD, DI and FI vines. No significant differences were found among the three irrigated treatments. Both maximum electron transport rate (Jmax; ca 30%) and triose-phosphate utilization rates (TPU; ca 20%) were significantly lower in NI and PRD vines than in DI and FI vines. Carbon isotope composition (δ13C) of grape berries was highest in NI vines (–24.3), followed by PRD (–25.4) and DI (–25.8) and lowest in FI (–26.4) vines, suggesting a long-term increase in the efficiency of leaf gas exchange in NI compared with PRD, DI and FI vines. Sap-flow data and estimates of relative stomatal limitation are in accordance with the observed stomatal closure in PRD vines. In this study, we show that PRD irrigation was able to maintain a vine water status closed to FI, but with double water use efficiency, which was due to a reduction of stomatal conductance with no significant decrease in carbon assimilation.
Cloning and expression of two plasma membrane aquaporins expressed during the ripening of grape berry
Authors: Picaud Sarah , Becq Frédéric , Dédaldéchamp Fabienne , Ageorges Agnès , Delrot Serge
Published: August 2003

The ripening of grape (Vitis vinifera L.) berry is accompanied by dramatic accumulation of sugars and water. Two full-length clones and several partial clones encoding plasma membrane aquaporins (PIP) were cloned from grape berries collected at the beginning of ripening. Based on their sequences, on a phylogenetic analysis and on functional properties, both clones, called VvPIP1a and VvPIP1b were assigned to the PIP1 subfamily. RNA gel blot studies with berries at various stages of development indicated that VvPIP expression was highest at stages following veraison. Injection of Xenopus oocytes with VvPIP1a cRNA induced a moderate increase of water permeability and a large increase in glycerol permeability, whereas injection with VvPIP1b cRNA did not affect these permeabilities. Injection of VvPIP1a cRNA, but not VvPIP1b cRNA, inhibited urea uptake by the oocyte, and this inhibition was sensitive to HgCl2. The data are discussed in relation with the potential role of aquaporins in fruit physiology.