Showing papers in "Crop & Pasture Science in 1984"
TL;DR: The relations between wheat yield and water use were determined from field measurements in South Australia by fitting the de Wit formula Y = m W/Ep, but the m factor varied with the proportion of water use that was lost by direct evaporation.
Abstract: The relations between wheat yield and water use were determined from field measurements in South Australia. Highest production of dry matter was 37 kg ha-1 per mm of water use and of grain was 12.7 kg ha-1 per mm. More than 70% of the total water use occurred by anthesis. Time of sowing and soil water content at sowing had a big influence on yield. The loss of water by direct evaporation was estimated to be 110 mm, equal to about one-third of the water use. The maximum efficiency of water transpired was 55 kg ha-1 mm-1 for dry matter and 20 kg ha-1 mm-1 for grain. The efficiencies of most of the crops were below this level. Yield (Y), water use (W) and evaporation (Ep) could be fitted to the de Wit formula Y = m W/Ep, but the m factor varied with the proportion of water use that was lost by direct evaporation.
638 citations
TL;DR: When two pastures with different sward characteristics were offered together, sheep generally preferred the one they could eat faster, and intake rate was several-fold greater when sheep grazed tall, sparse pastures than short, dense pastures.
Abstract: Boards of artificial pasture were prepared by threading the top two leaves of tillers from either ryegrass or kikuyu grass, in their vegetative stage of growth, through 5-mm-diameter holes in pressed hardwood sheets. The holes were spaced in rows from 10 to 50 mm apart, and, with one, two or three tillers per hole, tiller density ranged from 346 to 25 980/m2. Sward height was varied by pulling tillers different distances through the holes before they were fastened to the underside of the boards, and the mass of herbage dry matter ranged from 0.04 to 7.61 t/ha. In series I experiments, the effects of sward characteristics on ingestive behaviour of two sheep were examined, whereas, in series I1 experiments, pastures that were consumed at different rates were offered in pairs and the preference of one sheep observed. The rate of pasture intake was related to sward height only when tiller density was constant and to herbage mass per unit volume (bulk density) only at similar sward heights. Intake rate was better described by herbage mass per unit area but, at herbage availabilities of less than 1 t/ha, intake rate was several-fold greater when sheep grazed tall, sparse pastures than short, dense pastures. The best predictor of pasture intake rate was herbage mass per area effectively covered by one bite. Intake per prehending bite declined with a reduction in both sward height and density, and was also best described by herbage mass per area effectively covered by one bite. Prehending bite rate doubled as intake per bite declined from 200 to 10 mg dry matter. The rate of jaw movements during grazing was virtually unaffected by sward characteristics; prehending bites accounted for 20% of jaw movements when intake per bite was 200 mg dry matter and 80% of jaw movements with short, widely spaced swards. When two pastures with different sward characteristics were offered together, sheep generally preferred the one they could eat faster.
298 citations
TL;DR: 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, and the need for multi-factorial treatments to overcome all yield limitations and thereby attain the potential yield.
Abstract: 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.
226 citations
TL;DR: While both sodium and chloride concentrations of the shoot were lower in the tolerant than in less tolerant plants, chloride was more closely associated with salt tolerance than sodium.
Abstract: Variation existed between plants of the lucerne (Medicago sativa L.) cultivar CUF 101 for dry matter production, shoot number and length, and leaf damage when grown for 70 days under 250 mM NaCl (15 h photoperiod, 20¦C day, 10¦C night). Salt tolerance evaluation using the criteria percentage leaf damage (percentage of total number of leaves with complete or partial necrosis) and length of the main shoot, isolated plants which showed salt tolerance of reasonably high heritability (h2=0.41). Two generations of recurrent selection for tolerance significantly increased the mean population tolerance without decreasing production under non-saline conditions. While both sodium and chloride concentrations of the shoot were lower in the tolerant than in less tolerant plants, chloride was more closely associated with salt tolerance than sodium. Sodium and chloride concentrations in the roots did not vary with the level of salt tolerance. No association of shoot and root potassium concentration with tolerance was evident. Selection for salt tolerance in lucerne plants using percentage leaf damage of less than 10% as the main criterion should give a rapid response to selection. The efficiency of selection may be increased if selection is based on the efficiency of chloride exclusion from the shoots and/or the level of chloride tolerated by the shoots prior to leaf damage becoming evident.
149 citations
TL;DR: Equations developed to predict the preference for one forage over another on the basis of their relative intake rates, showed fair agreement with observations from experiment 1, particularly when the effects of acceptability factors such as taste, odour or feel were translated into differences in potential intake rate.
Abstract: In experiment 1, potential intake rates of several dried forages, varying widely in nutritive value, were measured by offering each alone to six hungry sheep for eight, separate 1-min periods. Intake rates ranged from 5.5 to 26.1 g/min, but, within each forage, it varied little between sheep (c.v. 13%) or between measurements with the same sheep (c.v. 8%). The forages were then offered in pairs in separate containers and preference for one forage was defined as the percentage of total intake derived from that forage. With the exception of a dried clover pasture, preference for a forage was strongly related to the rate at which it could be eaten. Reducing the length of wheaten straw particles from 30 to 10 mm increased intake rate from 5.5 to 12.4 g/min and resulted in an absolute preference for the short material. The mean preference for a forage over all comparisons was more strongly correlated with intake rate of the forage (r2 = 0.87) than with in vitro digestibility of organic matter (r2 = 0.30). In experiment 2, two wheaten straws and two wheaten hays were each chopped to two lengths and, within each forage, mixed (w/w) in the short : long ratios of 0 : 1, 1 : 2, 2 : 1 and 1 : 0. Mean intake rates were 7.3 and 12.5 g/min for the two straws and 15.7 and 23.2 g/min for the two hays. Within each forage, all mixtures were offered in pairs to establish preference. The slopes of regression equations relating preference (%) to intake rate (g/min) were 21.4, 17.0, 5.9 and 2.7 (%.min/g) for the four forages as mean intake rate increased from 7.3 to 23 2 g/min, which indicates that discrimination between forages with the same difference in intake rate was greater when mean intake rate was low. In experiment 3, finely ground clover pasture, lucerne hay, wheaten hay or wheaten straw were added to a base diet of either chopped lucerne or wheaten straw in the ratio 1 : 10. Although the additive had little effect on intake rate, sheep preferred lucerne to clover pasture and wheaten hay to wheaten straw. Equations developed from the results of experiment 2 to predict the preference for one forage over another on the basis of their relative intake rates, showed fair agreement with observations from experiment 1, particularly when the effects of acceptability factors such as taste, odour or feel were translated into differences in potential intake rate.
122 citations
TL;DR: Temperament scores were taken on 8-month-old calves from five calf drops and over three sections of a large crossbreeding trial on the North Coast of New South Wales and there were significant differences in temperament among calves sire breeds.
Abstract: Temperament scores were taken on 8-month-old calves from five calf drops (1976-80) and over three sections of a large crossbreeding trial on the North Coast of New South Wales. A 0-5 scale was used, with lower values for quieter cattle. The heritability ¦s.e. of temperament score of Bos taurus calves (sired by Hereford, Simmental and Friesian bulls) was 0.03¦0.28, and for B. indicus-sired calves (Brahman, Braford and Africander bulls) 0.46¦0.37, and for all data combined 0.44¦0.25. There was a significant difference (P < 0.01) between the mean score of Brahman-sired halfbred calves (1.96) and B. taurus-sired calves (1.05). The difference was halved to 0.45 points for quarterbred Brahman calves versus B. taurus calves, i.e. as expected for an additive trait. There were significant differences in temperament among calves sired by B. indicus bulls, but there were no significant differences amongst the B. taurus sire breeds. The repeatability (mean ¦ s.e.) of operators' score of 701 weaner calves was 0.67¦0.08. From temperament scores of 315 cows at weaning in 1981, an operator repeatability of 0.82¦0.08 was obtained. Correlations of cow and calf score were not consistent, but averaged 0.18¦0.04 from 547 records. The repeatability of scores taken at two separate times on 132 calves, was 0.43¦0.09. The group given a medium level of nutrition had significantly higher temperament scores than those given high or low levels. Sex effects were not significant on scores at weaning. A log transformation of the data equalized the variance of scores of different breeds, but did not affect the conclusions.
116 citations
TL;DR: The symbiosis of the root-nodules of Bragg soybean and the relative dependence of the plants on symbiotic and soil sources of N were evaluated, indicating that soybeans compensated for symbiotic deficiencies by more efficient exploitation of soil N and/or by moreefficient redistribution of vegetative N into grain N, and that nodulation and soil NO-3 were interactive and complementary in meeting the N requirements of the crop.
Abstract: The symbiosis of the root-nodules of Bragg soybean [Glycine max (L.) Merrill] and the relative dependence of the plants on symbiotic and soil sources of N were evaluated in an experiment conducted on a vertisol which was high in organic- and mineral-N, free of Rhizobium japonicum, and where poor nodulation was characteristic of inoculated, new sowings. Effective inoculant containing R. japonicum strain CB 1809 was sprayed into the seed bed at three rates of application (10-fold intervals). Increasing rates of inoculant led to greater numbers of rhizobia in the rhizosphere and in the soil, and to improved nodulation. Uninoculated plants did not nodulate. High soil NO-3 (30 ¦g N/g, top 30 cm) did not prevent prompt, abundant colonization of rhizospheres by the bacteria from the inoculant, but nodule initiation was delayed and nodule development was retarded until 42 days after sowing. There was an acceleration in nodule formation and development between 42 and 62 days which coincided with a depletion of NO-3 from the top 60 cm of the soil profile. Nodulated and unnodulated soybeans took up NO-3 at similar times and rates to a soil depth of 90 cm; only unnodulated plants utilized soil NO-3 below 90 cm. Vacuum-extracted stem (xylem) exudate was sampled from plants throughout growth and analysed for nitrogenous solutes. The proportion of ureide-N relative to total-solutes-N in xylem sap was used as an index of symbiotic N2-fixation. The initial increase in concentrations of ureides coincided with the period of accelerated nodule formation and development between 42 and 62 days. Thereafter, there was a progressive increase in ureide concentrations in nodulated plants, and the levels were related to rate of inoculation, extent of nodulation, and to the decline in concentrations of soil NO-3. Ureide concentrations in unnodulated plants remained low throughout. The quantities of NO-3-N and s-NH2- N in xylem sap were not related to nodulation. The differences between treatments in terms of whole-plant N and grain N were less than predicted from the symbiotic parameters. This indicated that soybeans compensated for symbiotic deficiencies by more efficient exploitation of soil N and/or by more efficient redistribution of vegetative N into grain N, and that nodulation and soil NO-3 were interactive and complementary in meeting the N requirements of the crop.
92 citations
TL;DR: The results show that the several processes which resulted in gaseous loss of N operated concurrently, commencing almost immediately after fertilizer application, with major microbiological transformations appeared to occur near the soil-water interface.
Abstract: 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).
92 citations
TL;DR: Water uptake by mature (post-dormancy) wheat grain was studied and grain germination after 30 h exposure to moisture was significantly correlated with its water uptake after 2 h of imbibition, usefully characterize in-ear sprouting.
Abstract: Water uptake by mature (post-dormancy) wheat grain was studied for a group of 50 wheat varieties of mostly Australian origin and in lines near-isogenic for grain coat colour (red v. white) and for hard v. soft grain. Cultivars differed widely (up to two-fold) in grain water uptake. Apparently these differences related to physico-chemical aspects of water imbibition by the grain. However, neither grain coat colour, pericarp or testa thickness, grain hardness nor grain protein content was correlated with grain water uptake. The degree of seed coat cracking was minimal as grain was dissected by hand from the ears. Grain germination after 30 h exposure to moisture was significantly correlated with its water uptake after 2 h of imbibition (r = 0.61). These findings, when combined with other information from this laboratory on varietal differences in ear water uptake, usefully characterize in-ear sprouting. Of the varietal differences in sprouting, 18% can be accounted for by differences in ear and grain water uptake. Differences in grain dormancy were deliberately avoided in these studies, but were evaluated separately at harvest ripeness in this same experiment. On the basis of varietal differences in grain dormancy and water uptake some breeding options are highlighted.
88 citations
TL;DR: Temperature had a marked effect on the disease severity and its effect varied with individual fungi and their combinations, in particular, combinations involving P. irregulare (severest root rot at 10 and 15¦C) and the most severe root rotting, compared with the control, occurred at 65% WHC.
Abstract: The effects of soil temperature (10, 15, 20 and 25¦C) and moisture (45% water holding capacity (WHC), 65% WHC, and flooding) on the pathogenicity of five fungi, both alone and in combinations, were investigated to determine the involvement of these fungi in a severe root rot disorder of subterranean clover in Western Australia. Fusarium avenaceum, Pythium irregulare, and Rhizoctonia solani were highly pathogenic while Fusarium oxysporum and Phoma medicaginis, particularly when used singly, were only weakly pathogenic. Compared with individual fungi, fungal combinations increased the severity of root disease and decreased plant survival and plant fresh weight. While the fungi investigated caused root rot over the range of soil temperatures and moisture conditions of this investigation, the most severe root rot occurred at 10¦C, with less at 15 and 25¦C, and least at 20¦C. Temperature had a marked effect on the disease severity and its effect varied with individual fungi and their combinations, in particular, combinations involving P. irregulare (severest root rot at 10 and 15¦C). The most severe root rotting, compared with the control, occurred at 65% WHC, with less at 45% WHC, and least under flooding conditions. There was often a significant interaction between temperature and moisture for the various fungi and fungal combinations tested.
81 citations
TL;DR: A species-area curve was constructed for buried viable weed seeds in a 5-year-old subterranean clover-annual ryegrass pasture in south-eastern Australia, suggesting that a sample whose size is sufficient for determination of species diversity of buried seeds is equally adequate for measuring buried seed density.
Abstract: A species-area curve was constructed for buried viable weed seeds in a 5-year-old subterranean clover-annual ryegrass pasture in south-eastern Australia A soil surface area of about 200 cm2 (to a depth of 10 cm) was required to obtain a representative individual sample (ie a replicate) of the number of taxa in the soil seed bank, whereas a combined area of about 1000 cm2 was required for adequacy within any treatment The total number of buried viable seeds of all species combined was distributed spatially in a more-or-less uniform manner This suggests that a sample whose size is sufficient for determination of species diversity of buried seeds is equally adequate for measuring buried seed density
TL;DR: 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, and deaths from exposure could be expected to exceed 30% in lambs born as multiples to Merino ewes.
Abstract: 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.
TL;DR: It is concluded that diets containing less than 1 % mimosine on a DM basis have little adverse effect on thyroid function or feed intake, whereas above this level hypothyroidism and low feed intakes may occur.
Abstract: Steers were fed in pens on diets containing 0, 10, 20, 40, 67 and 100% Leucaena for 112 days. The remainder of the diet was a good quality sorghum hay. Liveweight change, feed intake, mimosine intake, urinary output of 3-hydroxy-4(1H)-pyridone (DHP), serum thyroxine (T,), serum triiodothyronine (T3) and effective thyroxine ratio (ETR) were measured. Steers on the 67 and 100% Leucaena diets had low feed intakes (40-50 g (kg LW)-a 75), lost weight and were severely hypothyroid. Steers on the 0, 10 and 20% Leucaena had intakes of 80-90 g (kg LW)-a 75, gained liveweight at 0.3-0.5 kg day-' and showed normal thyroid function. Steers on the 40% Leucaena diet had high feed intakes and grew well initially, but subsequently their feed intakes and rates of liveweighr gain declined. Reduced feed intake was associated with serum T, levels below 1.0 nmol 1-I. DHP excretion in the urine was linearly related to Leucaena and mimosine intake (P < 0.01). Recoveries of mimosine eaten, as DHP in the urine, varied from 33% with the 10% Leucaena diet to 55% with full Leucaena feeding. Feed intake declined as the proportion of Leucaena in the diet increased, but recovery of appetite was rapid when steers were transferred to an all sorghum hay ration. It is concluded that diets containing less than 1 % mimosine on a DM basis have little adverse effect on thyroid function or feed intake, whereas above this level hypothyroidism and low feed intakes may occur. Under Australian conditions Leucaena can only safely be used as a supplement (<30%) to roughage diets, rather than as a major dietary component, until some solution to the toxicity problem is found.
TL;DR: Analysis of simple geometric models of wheat grains suggests that selection for optimal shape is likely to result in a correlated reduction in seed size thereby offsetting any gains achieved by changing seed shape.
Abstract: Simple geometric models of wheat grains have been analysed to determine the effects of changes In shape and size on volume per unit surface area and hence potential milling yield. These analyses suggest that substantial changes In grain volume would have a greater effect on milling yield than would changes in grain shape. The shape and size of kernels of current Australian cultivars differ markedly from the optimum required to maximize volume per unit surface area (1 e. a spherical gram) Available data on genetic variability for grain size indicates that it should be possible to increase the gram size of Australian wheats by 50-100% and improve potential milling yields by 2-3%. However, while considerable genetic variation for grain shape also exists, the evidence available suggests that selection for optimal shape is likely to result in a correlated reduction in seed size thereby offsetting any gains achieved by changing seed shape.
TL;DR: It appears that, when this soil type is not cultivated, drying will reduce P uptake mainly because mechanical resistance reduced root extension, and root extension ceased well within the available water range in intact soil cores.
Abstract: The effects of soil bulk density (±) and water content on root extension, phosphorus (P) uptake and plant growth were studied with ryegrass in pot experiments with a sandy loam soil. Uptake was considered in terms of a root cylinder model with parameters of root length and uptake per unit length. Increasing ± (from 1.0 to 1.54 g cm-3 ) slightly increased root diameter and reduced root hair length, but the main effect on uptake per unit length of root was related to the increased mass of soil and hence the increased mass of P within the root hair cylinder. The effect of ± on diffusion to the surface of the cylinder appeared to be small. Increasing ± also increased soil strength, causing a reduction in root length which was linearly related to P uptake. Thus the effect of ± on total P uptake was a product of the opposing effects on uptake per unit length and root length. The importance of these two effects was confirmed by calculating potential P uptake using a simple root cylinder model in which ± was a variable. Predicted and observed values were highly correlated (r2 = 0.94). Drying the soil reduced P uptake per unit length of root, but, in compacted soil, this effect was small compared with the effect of drying on root extension. It appears that, when this soil type is not cultivated, drying will reduce P uptake mainly because mechanical resistance reduced root extension, and root extension ceased well within the available water range in intact soil cores.
TL;DR: A survey for mycotoxins and fungal damage in maize (Zea mays L.) grown during 1982 in Far North Queensland is reported in this paper, where 293 samples examined came from 11 1 farms in eight maize-growing districts.
Abstract: A survey for mycotoxins and fungal damage in maize (Zea mays L.) grown during 1982 in Far North Queensland is reported. This season had a rainfall distribution which was typical for the reglon. The 293 samples examined came from 11 1 farms in eight maize-growing districts. The samples were first subjected to rapid screening tests for fungal damage. Aflatoxins B1, B2, G1, G2 ochratoxin A, T-2 toxin, and sterigmatocystin were not detected, but zearalenone was found in 85% of the samples.
The concentrations of zearalenone were correlated with the extent of Gibberella zeae cob rot as indicated by the proportion (up to 2%) of kernels in each sample having a reddish-purple discoloration. In four samples the zearalenone concentration exceeded 1 mg kg-1, but the mean ¦ s.d. (n = 293) concentration in all samples was 0.17 ¦ 0.225 mg kg-1. Concentrations were highest in districts with the highest rainfall during the period of maize growth.
TL;DR: It is suggested that the intake rate of dried forages may be a useful predictor of the preference for dry matter with forages containing any proportion of moisture, but further research is needed.
Abstract: The effects of dry matter content and particle length of forage on potential intake rate and preference by sheep were investigated using six animals held in metabolism cages. In experiment 1, freshly harvested kikuyu grass (Pennisetum clandestinum) in its vegetative state was mixed in different proportions with similar material that had been oven-dried to form 15 diets ranging in dry matter content from 15 to 94%. Intake rate of wet matter decreased from 60 to 14 g/min as dry matter content increased, whereas the intake rate of dry matter increased from 9 to 14 g/min as the dry matter content of forage rose to about 40% but remained relatively constant thereafter. In experiment 2, undried kikuyu grass was eaten faster and formed a greater proportion of total intake than did dried kikuyu when expressed on a wet matter basis, but the amount of dry matter consumed from each forage was similar when they were offered together in separate containers. Kikuyu chopped to 10-mm length was eaten faster and was also preferred over kikuyu cut to 40 mm, irrespective of its dry matter content. Factors other than intake rate such as taste, odour or feel did not contribute markedly to the preference for either undried or dried kikuyu. Equations developed previously using results from dried forages predicted preference from intake rate quite well for dried forage but not for undried forage. It is suggested that the intake rate of dried forages may be a useful predictor of the preference for dry matter with forages containing any proportion of moisture, but further research is needed.
TL;DR: The physical disintegration of five mature, chaffed roughages in chewing during eating was examined using four oesophageal-fistulated steers and some interactions occurred between the different roughages and individual steers.
Abstract: The physical disintegration of five mature, chaffed roughages (barley straw, oat straw, pea straw, ryegrass hay and lucerne hay) in chewing during eating was examined using four oesophageal-fistulated steers. Measurements were made of intake, chemical composition, modulus of fineness and grinding energy of the feeds, and of particle size distribution, modulus of fineness and the proportion of particles greater than 1 mm in the oesophageal extrusa. Significant differences between steers and between feeds occurred in modulus of fineness and the proportion of particles greater than 1 mm. Between steers, there were decreases, with chewing, of 30-40% in the mean proportion of particles greater than 1 mm. The order of proportionate particle size reduction for the different roughages was as follows: pea straw <: oat straw < ryegrass hay < lucerne hay < barley straw. Expressed in terms of the modulus of fineness, the mean decreases in particle size ranged from 46 to 52% for the different roughages. Some interactions occurred between the different roughages and individual steers. The critical characteristics responsible for the variation that occurred have not been defined either in the roughages or in the steers.
TL;DR: Germinability in harvest-mature wheat grain showed a marked dependence on temperature and decreased with increasing levels of grain dormancy, and the implications for the utilization of dormancy in the development of preharvest sprouting damage tolerant varieties and their subsequent use in practice are discussed.
Abstract: Germinability in harvest-mature wheat grain showed a marked dependence on temperature. The optimum temperature for the complete germination of all grains ranged from 20¦C for the non-dormant variety, Timgalen, to 10¦C for the strongly dormant red wheat RL 4137, whereas the optimum in terms of the shortest lag period ranged from 25¦ to 15¦C for the same varieties. Germinability gradually increased during post-harvest storage and, for after-ripened grain, the optimum temperature for both complete germination and shortest lag period were greater than 30¦C. Germinability could also be increased by pre-treating imbibing grains at temperatures of 5¦, 10¦ or in some cases 15¦C. This treatment was only effective for grain at moisture contents >25% (dry weight) and the effect was not reversed by redesiccation. The pre-treatment temperature required for maximum germinability decreased with increasing levels of grain dormancy. Complete removal of dormancy required a pre-treatment period of c. 48 h; however, lesser periods gave the shortest lag period in the case of the dormant varieties. The implications of these results for the utilization of dormancy in the development of preharvest sprouting damage tolerant varieties and their subsequent use in practice are discussed.
TL;DR: It is concluded that in M. lathyroides, C. pubescens, and possibly Schofield stylo, nodulation is more sensitive to aluminium toxicity than is host plant growth.
Abstract: Effects of aluminium concentrations of 0, 12.5, 25, 50, 100 or 125 ¦M on the nodulation and growth of Centrosema pubescens cv. Belalto, Macroptilium lathyroides cv. Murray, Stylosanthes guianensis cv. Schofield and Stylosanthes guianensis cv. Oxley were studied in solution cultures maintained at pH 4.5. The strains of Rhizobium used were CB1923, CB756, CB756 and CB1650 respectively. Solutions containing >25 ¦M aluminium (Al) delayed the appearance of nodules and reduced the percentage of plants which nodulated and the number and dry weight of nodules produced by all four legumes. At 125 ¦M Al, the proportion of plants which nodulated ranked in the order M. lathyroides (42%) > C. pubescens (29%) > Schofield stylo (16%) > Oxley stylo (0%). However, there were no significant effects of Al on dry matter production in M. lathyroides or C. pubescens. In Schofield stylo 250 ¦M A1 caused a small but significant yield reduction. In Oxley stylo, the yield reduction was significant at 25 ¦M , but became large only at 125 ¦M. It is concluded that in M. lathyroides, C. pubescens, and possibly Schofield stylo, nodulation is more sensitive to aluminium toxicity than is host plant growth. In Oxley stylo, threshold concentrations were similar for significant effects of aluminium toxicity on nodulation and growth.
TL;DR: The results indicate that soil tillage associated with cropping should build up a useful soil seed reserve of the harder seeded varieties, making them more amenable to softening once they are subjected to wide diurnal temperature fluctuations.
Abstract: Burrs of eight varieties of subterranean clover (Trifolium subterraneum L.), which had experienced one summer at the soil surface, were placed on the soil surface and at depths of 2, 6 and 10 cm in the soil. The numbers of residual hard seeds were determined after 1, 2 and 3 years. The effects of laboratory treatment at a diurnally fluctuating temperature of 60/15¦C on the softening of buried seeds and of seeds stored in the laboratory for 1 and 3 years were determined. Rate of seed softening in all varieties decreased with increasing depth of burial, apparently because the soil insulated the seeds from high soil surface temperatures. Few seeds of the varieties Northam and Geraldton softened during 3 years of burial at 6 or 10 cm; while, at the other extreme, few seeds of Yarloop survived 3 years at any depth. Some evidence was found for microbial decomposition of hard seeds in the field. Seeds softened more readily at 60/15¦C (in the laboratory) as the preceding periods of either laboratory storage or field burial increased. Such storage or burial experiences have a preconditioning effect on hard seeds, making them more amenable to softening once they are subjected to wide diurnal temperature fluctuations. The results indicate that soil tillage associated with cropping should build up a useful soil seed reserve of the harder seeded varieties.
TL;DR: A range of crop plants, pasture legumes and weeds, mostly with yellows symptoms similar to those caused by luteoviruses, were collected from the field around Tasmania and checked for infection with beet western yellows virus (BWYV) and subterranean clover red leaf virus (SCRLV) using aphids and indicator plants.
Abstract: A range of crop plants, pasture legumes and weeds, mostly with yellows symptoms similar to those caused by luteoviruses, were collected from the field around Tasmania and checked for infection with beet western yellows virus (BWYV) and subterranean clover red leaf virus (SCRLV) using aphids and indicator plants. BWYV was recovered from 216 of 897 plants tested, representing 30 different species and including 16 not previously recorded as natural hosts. SCRLV was recovered from 163 of 637 plants, representing twelve species including four not previously recorded as natural hosts. BWYV was isolated most often from composites and crucifers, while SCRLV was recovered most frequently from legumes. Eight plants were found infected with both viruses together. In host range studies, Tasmanian isolates of BWYV caused symptoms in lettuce, subterranean clover and sugar beet like those seen on these plants in the field from which the virus was isolated, and were thus similar to isolates of BWYV from North America. The Tasmanian isolates of BWYV were also closely related serologically to Californian isolates of BWYV; these were serologically quite distinct from isolates of SCRLV, and both these groups were serologically distinct from legume yellows virus and from potato leaf roll virus.
TL;DR: There was a direct relationship between mean linear growth rate of isolates from Fitzroy in pure culture, and virulence on Fitzroy, and the recovery ofhighly virulent Isolates from pods of a Fitzroy seed crop is discussed in relation to the rapid spread of highly virulent physiologic races.
Abstract: A survey of anthracnose of Stylosanthes scabra cvv. Fitzroy and Seca, caused by Colletotrichurn gloeosponoides, at 31 sites in Queensland found a wide range of disease severity. Disease was present at each of the 26 sites surveyed for Fitzroy, and inoculation experiments with an isolate from each site indicated that the isolates varied markedly in their virulence on Fitzroy. Some of the variation in disease severity between sites could be explained by differences In virulence of the isolates. Disease was observed In only one of the five fields of Seca surveyed. When nine of the isolates from Fitzroy were tested on SIX genotypes of S. scabra, there was no evidence of pathogenic specialization, and all isolates were avirulent on Seca. The isolate from Seca, when tested on the same genotypes, was moderately virulent on Seca and highly virulent on Fitzroy, indicating further pathogenic specialization within the Type A forms of C. gloeosporioides in Australia. There was a direct relationship between mean linear growth rate of isolates from Fitzroy in pure culture, and virulence on Fitzroy. The recovery of highly virulent Isolates from pods of a Fitzroy seed crop is discussed in relation to the rapid spread of highly virulent physiologic races.
TL;DR: The relationship between grain yield and grain quality was studied amongst sets of random Fj lines from seven wheat crosses, indicating that high-yielding, good-quality wheats could be obtained from the population.
Abstract: The relationship between grain yield and grain quality was studied amongst sets of random Fj lines from seven wheat crosses. The quality measures used included grain hardness, flour yield, flour protein content, farinograph and extensograph properties, and small-scale empirical measures such as Zeleny and sodium dodecyl sulfate sedimentation volume, residue protein content, and Pelshenke fermentation time. A significant negative correlation was found between grain yield and flour protein content. Thus selection for either characteristic would be to the detriment of the other. However, grain yield was not significantly correlated with the other quality measures, indicating that high-yielding, good-quality wheats could be obtained from the population. Most of the small-scale tests were correlated with farinograph and extensograph properties, but the correlation coefficients were not as high as those obtained with varieties or advanced breeding lines. The relationships were not dependent on differences in flour yield, grain hardness or flour protein content, thereby simplifying their application to breeding programs. Concurrent breeding for higher grain yield and improved functional quality would appear feasible. However, flour protein content would, at best, be maintained at current levels as yield increased.
TL;DR: It is concluded that lignin may be preferable to 103Ru-P as a particulate marker when certain coarsely chopped roughages are given to sheep, and when samples of digesta from the abomasum are obtained through a simple cannula.
Abstract: Five sheep with simple cannulae in the rumen and abomasum were given a diet of chopped oaten hay at 95-98% of ad libitum intake from continuously moving belts. Flows of digesta from the abomasum were estimated by a double marker method by reference to 51Cr-EDTA as the fluid marker, and either 103Ru-P, lignin, or acid insoluble ash (AIA) as the particulate marker. Estimates were also made by reference to lignin as a single marker. Estimates of the weight of digesta leaving the abomasum daily were unaffected by the choice of particulate marker when used with 51Cr-EDTA, but were 25% lower when lignin was used alone. The estimated flows of dry matter and acid detergent fibre (ADF) were dependent upon the choice of markers. Compared with estimates of ADF flow given by 51Cr-EDTA and lignin, estimates given by AIA were lower (-24.6%) and those given by 103Ru-P were higher (+26.2%). Lignin alone gave estimates 1.6% higher. Observations on the distribution of 103Ru-P in digesta dry matter indicated a markedly higher concentration on fine than on large particles. It is concluded that lignin may be preferable to 103Ru-P as a particulate marker when certain coarsely chopped roughages are given to sheep, and when samples of digesta from the abomasum are obtained through a simple cannula.
TL;DR: Stress due to high day temperatures before flowering prevented early flowers from developing pods, but later flowers were able to compensate, and the adaptability of the narrow-leafed lupin plant is discussed in view of environmental restraints.
Abstract: Plants of Lupinus angustifolius cv. Unicrop, with branches excised to eliminate competition between branches and the primary inflorescence, were exposed to three temperature treatments: 33/28, 33/13 and 18/28¦C. Each treatment continued for 1, 3 or 5 days, and was begun as flowers were starting to open, or 5 days before, or 10 days after that time. Control plants remained at 18/13¦C throughout. Stress due to high day temperatures before flowering prevented early flowers from developing pods, but later flowers were able to compensate. Temperature stress as flowering began substantially reduced numbers of seed-containing pods, and little compensation was observed, either in later pod set or in seed number per pod. After flowering, high day temperatures did not affect the most developed pods, but ovule abortion reduced seed production in the less developed pods. These findings are discussed in relation to assimilate availability and hormone effects, and the adaptability of the narrow-leafed lupin plant is discussed in view of environmental restraints. Breeding implications are briefly considered.
TL;DR: The concentration of copper in the youngest fully emerged leaf was a sensitive and accurate indicator of the copper status of wheat and the critical concentration for copper in this leaf did not change with the age of the plant.
Abstract: A glasshouse experiment was conducted to define critical concentrations of copper in young leaves of wheat and to investigate the effect of water stress after anthesis on the relationship between yield and copper concentrations in young leaves. The concentration of copper in the youngest fully emerged leaf was a sensitive and accurate indicator of the copper status of wheat. The critical concentration for copper in the youngest fully emerged leaf did not change with the age of the plant. Copper deficiency occurred whenever the concentration of copper in the youngest fully emerged leaf fell below 1.3 ¦g g-I (dry weight). Water stress after anthesis did not change the relationship between copper concentrations in young leaves and grain yield, although this stress markedly decreased grain yield. In the field there was considerable variability among plants given the same copper treatment in copper concentrations in young leaves. Nevertheless, whenever copper deficiency decreased growth, the average concentration of copper in the youngest fully emerged leaf was less than 1.3 ¦g g-1.
TL;DR: Isozyme surveys should provide critical evidence on the role such factors as introduction, natural selection, mutation and outcrossing have had in the origin of variation within subterranean clover in Australia.
Abstract: Isozyme patterns for the 22 registered cultivars of Trifolium subterraneurn L. are described for 15 enzymes. The patterns discriminated among all cultivars except that Uniwager was isozymically identical with Geraldton, from which it was derived by deliberate mutation. The 17 cultivars which originally came from naturally occurring isolates, as well as Uniwager, appeared to be isozymically homogeneous, whereas three of the five bred cultivars (Nungarin, Esperance and Howard) were polymorphic for at least one locus. The cultivars indicated that T. subterraneum is highly polymorphic at isozyme loci. Excluding the complex esterase patterns, the species was polymorphic at 21 of 26 putative loci, with an average of 2.3 alleles detected per locus. Estimates of genetic distance between the cultivars stemming from natural isolates strongly supported the classification into three subspecies. In addition, the cultivar Woogenellup (syn Marrar) was well separated from all other cultivars of the subspecies subterraneum. Isozyme surveys should therefore provide critical evidence on the role such factors as introduction, natural selection, mutation and outcrossing have had in the origin of variation within subterranean clover in Australia.
TL;DR: Segregation within some S, progenies for stipule hairiness and for disease reaction suggests that at least some natural outcrossing was occurring in the sampled S. guianensis population.
Abstract: Sixteen first-generation selfed (S,) progenies from Stylosanthes guianensis plants collected from a natural population were inoculated with each of 16 Colletotrichum gloeosporioides isolates in a replicated glasshouse experiment. Both host and pathogen collections were obtained from a single site in the Department of Valle, Colombia (76" 25'W.; 3' 55'N.; altitude 1720 m). Genetic differences among S, progenies were detected based on differential disease reaction and on phenotypic differences in two morphological characters. No evidence of major resistance gene effects among or within S, progenies was found. Both quantitative and qualitative differences among C. gloeosporioides isolates were detected: one isolate type was uniformly pathogenic across the S, progenies, while a second type elicited large differences in resistance among the progenies. ~ulturai characteristics of the isolates also differed. Segregation within some S, progenies for stipule hairiness and for disease reaction suggests that at least some natural outcrossing was occurring in the sampled S. guianensis population. The implications of the results with respect to the design of a disease control strategy for S. guianensis cultivars are discussed.
TL;DR: Echlum feeding induced a high rate of destruction of pyrrolizidine alkaloids in the sheep rumen, and the conversion of the Echium alkaloid metabolites by microsomal preparations from livers of the experimental sheep taken at necropsy was unaffected by the feeding schedule.
Abstract: Groups of 10 Merino wethers were pen-fed pelleted diets containing 80 or 20% Echium plantagineum, for four periods of 12 weeks alternating with four similar periods on control diet. Mild liver damage, characteristic of pyrrolizidine alkaloid poisoning, aas induced in one wether consuming 80% E. plantagineum. The other animals on the 80% diet showed only a small increase in the size of the hepatocytes, which was not unequivocally due to alkaloids. There were no effects on liver function, serum enzymes, weight gain or wool growth attributable to alkaloids. The 80 and 20% Echium diets contained 0.11-0.15 and 0.032-0.047% alkaloid respectively, indicating that approximately onequarter to one-third of the alkaloid of the fresh plant was lost during diet preparation and storage. Echlum feeding induced a high rate of destruction of pyrrolizidine alkaloids in the sheep rumen. The conversion of the Echium alkaloids into pyrrolic metabolites by microsomal preparations from livers of the experimental sheep taken at necropsy was unaffected by the feeding schedule.